Effects of habitat types and within lake environmental gradients on the diversity of chironomid assemblages

Publication date: Available online 30 May 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Diána Árva , András Specziár , Tibor Erős , Mónika Tóth
Understanding the distribution of biotic diversity across various spatial scales and environmental gradients is important from fundamental, practical and conservation biological aspects. We applied a hierarchical diversity partitioning framework to quantify the variability of sample level α- and β 1 -diversity, and environment related β 2 -diversity of benthic chironomid assemblages within and among a priori defined habitat types, and along the gradients of individual environmental factors in a large and shallow lake (Lake Balaton, Hungary). Taxon richness (both additive and multiplicative) and Shannon index based diversity approaches yielded highly concordant results. The α-diversity was much lower and β 1 -diversity higher than predicted by null model and both measures varied substantially among habitat types and along most individual environmental gradients. The β 2 -diversity indicated a marked variability of taxon (identified at species to genus level) pool among habitat types and higher than predicted taxon turnover along all examined environmental gradients. Moreover, the observed β 2 -diversity varied greatly among individual environmental gradients. The difference between the expected and observed β 2 -diversity values suggests that taxon turnover was most influential (in decreasing order) along the algae coverage gradient, the lake bed substratum gradient and the macrophyte coverage gradient among others. We argue that within-lake environmental heterogeneity and its effect on the taxon richness should receive more attention in biodiversity assessment and conservation. Management could benefit from the identification of within lake gradients along which taxonomic turnover maximizes.

Dynamics and sources of dissolved organic carbon during phytoplankton bloom in hypereutrophic Lake Taihu (China)

Publication date: Available online 29 May 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Linlin Ye , Xiaodong Wu , Bo Liu , Dezhi Yan , Fanxiang Kong
To establish the influence of phytoplankton blooms on the dynamics and sources of dissolved organic carbon (DOC) in Lake Taihu, the concentrations and stable carbon isotope values (δ13C) of DOC and particulate organic carbon (POC) were analyzed, along with environmental factors, including water temperature, chlorophyll a (Chl a ) concentration, phytoplankton community and total bacterial abundance, from March to August 2013 at five sites in Lake Taihu. Significant differences were observed in the DOC concentrations and δ13C DOC values at the sampling sites. On average, the proportion of DOC in the total organic carbon (TOC) pool ranged from 30% ± 10% to 81% ± 7%. POC was positively associated with both Chl a concentration and cyanobacteria biomass, suggesting that cyanobacteria blooms contribute to the POC pool in Lake Taihu. Depleted 13C in DOC relative to POC was observed in August, indicating that DOC was partially derived from POC in August. However, Chl a explained only 40% of the variation in DOC in the entirety of Lake Taihu, and at two sites far from the estuary, the contribution of allochthonous carbon was less than 50% in August. These results suggested a greater influence of allochthonous sources on the DOC pool. Moreover, the biodegradability of DOC was further determined by the total dissolved carbohydrates to DOC ratio (TCHO/DOC), specific UV absorbance (SUVA 254 ), and the concentrations of bioavailable DOC (BDOC). On average, 17% of the variation in DOC was attributable to the BDOC pool, and the BDOC concentration correlated positively with Chl a , cyanobacteria biomass, and total bacterial abundance, suggesting that cyanobacteria – derived DOC is biodegradable and is preferentially utilized by bacteria.

Impacts of hydroelectric power stations on Trichoptera assemblages in four rivers in NW Spain

Publication date: Available online 23 May 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Romina Álvarez-Troncoso , Cesar João Benetti , Amadou Babacar Sarr , Amaia Pérez-Bilbao , Josefina Garrido
In this work, we studied Trichoptera assemblages in different rivers in NW Spain affected by hydroelectric power stations, and assessed the influence of environmental variables on the distribution of species. Twenty sites in four rivers were sampled during eight sampling campaigns (2001-2002). The fauna was collected with a quantitative Surber sampler. In addition, several physical, chemical and habitat variables were measured at each site. A distance-based redundancy analysis (dbRDA) was done to investigate the relationship between the assemblages and the environmental variables. Assemblage composition was analyzed by non-metric Multi-Dimensional Scaling (NMDS) and differences between groups were tested using the analysis of similarity (ANOSIM) considering two grouping variables, the river basin and the position of the site (location). The SIMPER routine was used to verify species contribution to dissimilarity. A total of 53 taxa of Trichoptera belonging to 16 families were found, 52% of which were Iberian endemics. The dbRDA revealed that altitude, conductivity, total suspended solids, temperature and location were the variables that most influenced the studied fauna. According to the NMDS analysis, significant differences in faunal composition were recorded between up and downstream sites and between river basins. The fauna seems to respond to a longitudinal gradient, but also to the impact of hydropower stations. The main effects we observed were variations in water temperature and changes in fauna composition, which may be due to the presence of hydropower stations.

Stream macroinvertebrate communities change with grassland afforestation in central Argentina

Publication date: Available online 23 May 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): J.A. Márquez , L. Cibils , R.E. Principe , R.J. Albariño
Lotic ecosystems are highly affected by land use changes such as afforestation of natural areas for management or commercial purposes. The aim of this study was to analyse the effect of pine plantations on benthic invertebrate communities in mountain grassland streams. Additionally, we assessed if the hydrological period modifies the effect of afforestation on stream invertebrates. Three headwater streams draining grasslands (reference streams) and three draining plantations of Pinus elliottii were selected in a mountain watershed of Córdoba province (Argentina). Hydrologic and physicochemical variables were registered and benthic invertebrate samples were collected in each stream at two different hydrological periods. Total invertebrate abundance, richness and diversity were reduced in afforested streams as well as the number of indicator taxa. In addition, invertebrate functional structure (i.e. taxonomic richness and total and relative abundance of Functional Feeding Groups, FFG) showed differences between streams with different riparian vegetation and between hydrological periods. Total abundance of all FFGs was lower in afforested streams and scraperś relative abundance was higher in grassland streams at the low water period. In addition, in most FFGs richness was diminished in afforested streams. Changes in light intensity, hydrology and coarse organic matter inputs produced by afforestation alter fluvial habitats and consequently the composition and trophic structure of invertebrate communities in grassland streams of Córdoba mountains.

Inter-basin dispersal through irrigation canals explains low genetic structure in Diplomystes cf. chilensis, an endangered freshwater catfish from Central Chile

Publication date: Available online 19 May 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): C.P. Muñoz-Ramírez , P.F. Victoriano , E. Habit
Biotic homogenization in freshwater ecosystems is a growing concern among conservation biologists. Recent phylogeographic data has shown low genetic structure between some basins from Central Chile, hypothesizing that either current dispersal through irrigation canals or incomplete lineage sorting due to recent divergence might explain the observed patterns. However, these hypotheses remain untested despite their potential implications for freshwater biodiversity and conservation. We used a statistical, model-based framework (approximate Bayesian computation) to investigate the relative support for each of these hypotheses. Our results show strong support for the model involving current migration between basins, and rejected the model of recent divergence without migration. These results strongly suggest that irrigation canals are facilitating the dispersal between basins, posing a serious threat to biodiversity in Central Chile, an area considered a biodiversity hotspot. Finally, these results highlight the utility of model-based approaches for determining demographic processes with potential conservation implications, even with the lack of extensive molecular data.

Decomposition of macrophytes in a shallow subtropical lake

Publication date: Available online 19 May 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Cristiane Carvalho , Luiz Ubiratan Hepp , Cleber Palma-Silva , Edélti Faria Albertoni
Submerged macrophyte detritus is a major component of the organic matter entering shallow lakes. Plant litter decomposition is a complex process that is mediated by microorganisms and some invertebrates. However, the role that aquatic organisms play in the decomposition of macrophytes in shallow subtropical lakes is unclear. This study compared the decomposition rates of Potamogeton pectinatus and Chara zeylanica in a shallow lake (southern Brazil) and assessed the fungal biomass and the macroinvertebrate community associated with the detritus. Aliquots of both species were incubated in litter bags and placed in the lake. After 1, 7, 20, 40, 60, and 80 days of incubation, one set of litter bags was removed from the lake. In a laboratory, plant material was washed for the determination of decomposition rates, chemical characterisation, and quantification of microorganisms and invertebrates. After 80 days of incubation, there was no C. zeylanica detritus, with a decomposition that was four times faster than that of P. pectinatus . The chemical composition was also different between the two detritus, with P. pectinatus showing a higher concentration of nitrogen, phosphorus, organic matter, polyphenols, and carbon. The fungal biomass was similar between the two species. In total, 7,502 invertebrates belonging to 27 taxa were sampled in this study. The composition and abundance of invertebrates was different between the two species. In conclusion, the chemical structure of the macrophyte species studied was important for the microorganisms’ and invertebrates’ colonisation. In addition, leaching had an important function in the initial degradation process.

Dietary-morphological relationships of nineteen fish species from an Amazonian terra firme blackwater stream in Colombia

Publication date: Available online 29 April 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Fernando Ramírez , Thomas Lee Davenport , José Iván Mojica
Small, oligotrophic Amazonian streams support an extremely rich fish fauna. The aim of the current study was to elucidate the relationship between diet and morphology in fishes from an Amazonian terra firme stream in the Colombian Amazon River basin near the city of Leticia. Fish specimens were collected from two locations at the Yahuarcaca terra firme stream. All fish species selected in the morphological analyses were used in the dietary analyses. We analyzed 10 to 60 adult individuals per species based on availability. Morphology and diet were correlated by direct observation (description) of morphological structures and food items found in gut. Only morphological variables presumed to be associated with prey capture and feeding were recorded for each individual. Species diets were classified into six food categories based on stomach content analysis. By comparing morphological characteristics, and dietary data, it was possible to find a relationship between structures and feeding habits and propose a model for explaining these relationships. Morphological and dietary specializations were found among some fishes inhabiting the stream examined. Internal morphological characteristics such as gill rakers, pharyngeal teeth, pyloric caeca and stomach form should be used more often in ecomorphological studies because they are directly associated with resource utilization and linked to feeding habits.

Variation in diet across an elevational gradient in the larvae of two Hydropsyche species (Trichoptera)

Publication date: Available online 17 April 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Thomas Bing , Jörg Müller , Bruno Glaser , Roland Brandl , Martin Brändle
While specialized species are linked to a particular resource, omnivorous species may switch between food items according to the availability and the quality of resources. Here we use larvae of the omnivorous caddisfly genus Hydropsyche (Trichoptera) to analyse changes in diet composition across an elevational gradient. Periphyton and Hydropsyche larvae were sampled from 22 populations at stream orders from 2 to 5 on the German part of the Bohemian Forest. Elevations of sampling sites ranged between 300 m and 900 m a.s.l. Diet composition was estimated by the analyses of the gut content of larvae as well as by stable nitrogen isotopes (δ15N). The δ15N values of the periphyton decreased and the C/N ratio of periphyton increased with increasing environmental harshness (decreasing water pH, temperature and conductivity with increasing elevation) indicating a decrease of periphyton food quality. Across individuals, the proportion of animals in the gut of Hydropsyche larvae was positively related to the difference of δ15N values between larvae and periphyton. The proportion of animals within the gut and (baseline corrected) δ15N values of Hydropsyche populations increased with increasing environmental harshness. We suggest that the (i) low primary production caused by shading, low temperatures and low nutrient levels, (ii) the low nutrient quality of periphyton and (iii) the availability of animal prey due to the input of allochthonous resources in headwaters caused the shift in the diet of Hydropsyche larvae along the river continuum.

Selective predation by benthivorous fish on stream macroinvertebrates – The role of prey traits and prey abundance

Publication date: May 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 52
Author(s): Susanne Worischka , Susanne Isabel Schmidt , Claudia Hellmann , Carola Winkelmann
The prey selectivity of fish depends largely on traits of the prey and the predator. Preferable prey traits might be different for visual predators (such as drift-feeding salmonids) and rather non-visual predators (such as benthic feeders). We evaluated the explanatory power of five prey traits and prey long-term abundance for the prey selection of small benthivorous fish by analysing the macroinvertebrate community and the diet of gudgeon ( Gobio gobio ) and stone loach ( Barbatula barbatula ) in two small submontane streams. Fuzzy principal component analyses, as well as electivity indices, revealed that the fish fed selectively. Prey size and feeding type were the most descriptive variables for the fish diet, followed by mean abundance, whereas microhabitat preference, locomotion mode and current velocity preference were less important. The fish preferred prey that was both small and consistently abundant, grazers and sediment feeders. Larger prey and shredders were avoided. The selection patterns of both fish species differed from those of visual fish predators but strongly resembled each other. Supporting this, in gudgeon which feeds slightly more visually than the strictly nocturnal stone loach, selectivity concerning prey traits as well as prey mean abundance was slightly more pronounced. We analyzed also selectivity for prey clusters based on the three most important variables. The observed selectivity patterns concerning these clusters were less pronounced but supported the other results. The maximum (neutral) electivity index was that of gudgeon for small, abundant grazers or sediment feeders, including chironomids. We conclude that prey selection of benthivorous fish that forage mainly non-visually can largely be explained by a small number of prey traits which probably work in combination. The prey preferences of these predators seem to be closely connected to their active foraging mode and to depend partly on the ability to detect prey visually.

Neuston: A relevant trophic resource for apple snails?

Publication date: Available online 7 April 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Lucía Saveanu , Pablo R. Martín
Apple snails are known for the strong impacts they provoke in wetlands and aquatic crops by their macrophytophagous habits. Interestingly, they are able to persist after they have eradicated most palatable aquatic macrophytes in the invaded wetlands. Pedal surface collecting is a distinctive mechanism that apple snails use to capture materials in the water surface. We were interested in knowing the relevance of neuston, the organisms associated with the air-water interface, as an alternative trophic resource. Using the invasive Pomacea canaliculata as a model, our experiments with simulated trophic resources in the laboratory showed that neuston is highly consumed even in the presence of abundant palatable macrophytes. P. canaliculata was able to grow efficiently using neuston as an alternative trophic resource both under laboratory and natural conditions. Neuston probably plays a relevant role specially when other trophic resources are inedible or absent or have been depleted by apple snails. Pedal surface collecting probably evolved in apple snails as an adaptation to cope with fluctuating trophic resources.

Habitat suitability of the invasive water hyacinth and its relation to water quality and macroinvertebrate diversity in a tropical reservoir

Publication date: Available online 7 April 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Tien Hanh Thi Nguyen , Pieter Boets , Koen Lock , Minar Naomi Damanik Ambarita , Marie Ane Eurie Forio , Peace Sasha , Luis Elvin Dominguez Granda , Thu Huong Thi Hoang , Gert Everaert , Peter L.M. Goethals
In this study, we assessed the relationship between the occurrence of the invasive water hyacinth ( Eichhornia crassipes ) and water quality properties as well as macroinvertebrate diversity in a tropical reservoir, situated in western Ecuador. Macroinvertebrates and physico-chemical water quality variables were sampled at 32 locations (during the dry season of 2013) in both sites covered and non-covered by water hyacinth in the Daule-Peripa reservoir. The results indicated that, in terms of water quality, only turbidity was significantly different between sampling sites with and without water hyacinth (Mann-Whitney U-test, p < 0.01). The habitat suitability model showed that water hyacinth was present at sites with a low turbidity. The percentage water hyacinth cover increased with decreasing turbidity. The Biological Monitoring Working Party-Colombia score and the Margalef diversity index were significantly higher (Mann-Whitney U-test, p < 0.01) at sampling sites where water hyacinth was present compared to water hyacinth absent sites. However, there were no significant differences in the Shannon–Wiener index, Evenness index and Simpson index between the sampling sites with and without water hyacinth. Our results suggest that water hyacinth cover was an important variable affecting the diversity of macroinvertebrates in the Daule-Peripa reservoir, with intermediate levels of water hyacinth cover having a positive effect on the diversity of macroinvertebrates. Information on the habitat suitability of water hyacinth and its effect on the physico-chemical water quality and the macroinvertebrate community are essential to develop conservation and management programs for large tropical reservoirs such as the Daule-Peripa reservoir and the Guayas river basin, where water resources are being at high risk due to expansion of agricultural and industrial development activities.

Climate driven changes in the submerged macrophyte and phytoplankton community in a hard water lake

Publication date: Available online 3 April 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Wojciech Ejankowski , Tomasz Lenard
We studied the changes in the submerged aquatic vegetation (SAV) and phytoplankton community in a hard water lake during different meteorological conditions. We hypothesised that variations in climatic conditions (precipitation and temperature) can influence the physicochemical parameters of water and, in turn, affect SAV and phytoplankton development. The investigations were performed in Lake Rogóźno (the West Polesie region, Eastern Poland) over 10 years from 2003 to 2013. The physicochemical parameters, the structure of macrophytes and the phytoplankton community in the dry (2003-2006, DP) and wet periods (2007-2013, WP) were analysed. Between the dry and wet periods, the water colour and the concentration of dissolved organic carbon (DOC) increased considerably, whereas water conductivity decreased. Other parameters (concentration of nutrients, water reaction and transparency) were comparable during both periods. When the precipitation and water level were low (DP), charophytes dominated the SAV and cyanobacteria dominated the phytoplankton community. After the precipitation and water level increased (WP), the charophyte population declined and the vascular plants and bryophytes dominated. Furthermore, flagellated algae belonging to the dinophytes and cryptophytes were the most numerous in the phytoplankton community. These changes in the SAV and phytoplankton were linked with the variations of physicochemical parameters determined by the total precipitation and mean air temperature in March.

Morphometric variation of the oriental river prawn (Macrobrachium nipponense) in Taiwan

Publication date: Available online 20 March 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Po-Cheng Chen , Tzong-Der Tzeng , Chun-Han Shih , Ta-Jen Chu , Ying-Chou Lee
Morphometric differences were used to elucidate the stock geographic variations and phylogeography of Macrobrachium nipponense in Taiwan. Eight samples were collected from three estuaries (Tamsui River Estuary [TSE], Kaoping River Estuary [KPE], and Houlung River Estuary [HLE]) and five reservoirs (Shimen Reservoir [SMR], Mingde Reservoir [MDR], Deji Reservoir [DJR], Tsengwen Reservoir [TWR], and Chengqing Lake Reservoir [CLR]). Twelve morphometric measurements were size-standardised by the allometric method and analysed via cluster analysis and canonical variate analysis (CVA). Randomisation tests were used to verify the morphometric variation between groups. The results clustered the eight samples into a minimum of three groups. The first group included four reservoir samples (i.e. DJR, MDR, CLR, and TWR); the second included the SMR sample, and the third comprised the remaining estuarine samples (i.e. TSE, HLE, and KPE). Morphometric variation among the three groups was significant for each sex. Significant differences between these three groups may be derived from evolutionary origins, geographic events or environmental adaption which was discussed in the paper. The difference between multivariate allometric coefficients in both sexes and sites were also tested based on the eight group data sets, and the result showed that the difference between sexes was significant.

A sensitivity analysis of lake water level response to changes in climate and river regimes

Publication date: March 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 51
Author(s): Ali Torabi Haghighi , Bjørn Kløve
Lake water level regimes are influenced by climate, hydrology and land use. Intensive land use has led to a decline in lake levels in many regions, with direct impacts on lake hydrology, ecology and ecosystem services. This study examined the role of climate and river flow regime in controlling lake regimes using three different lakes with different hydraulic characteristics (volume-inflow ratio, CIR). The regime changes in the lakes were determined for five different river inflows and five different climate patterns (hot-arid, tropical, moderate, cold-arid, cold-wet), giving 75 different combinations of governing factors in lake hydrology. The input data were scaled to unify them for lake comparisons. By considering the historical lake volume fluctuations, the duration (number of months) of lake volume in different ‘wetness’ regimes from ‘dry’ to ‘wet’ was used to develop a new index for lake regime characterisation, ‘Degree of Lake Wetness’ (DLW). DLW is presented as two indices: DLW 1 , providing a measure of lake filling percentage based on observed values and lake geometry, and DLW 2 , providing an index for lake regimes based on historical fluctuation patterns. These indices were used to classify lake types based on their historical time series for variable climate and river inflow. The lake response time to changes in hydrology or climate was evaluated. Both DLW 1 and DLW 2 were sensitive to climate and hydrological changes. The results showed that lake level in high CIR systems depends on climate, whereas in systems with low CIR it depends more on river regime.

Underwater light climate, thermal and chemical characteristics of the tropical soda lake Chitu, Ethiopia: Spatio-temporal variations

Publication date: May 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 52
Author(s): Tadesse Ogato , Demeke Kifle , Brook Lemma
Soda lakes are known for their extreme environmental conditions and unique assemblage of biota and provide great ecological and economic values. Although they are highly sensitive to environmental changes, soda lakes are among the least frequently studied inland water bodies. In this study, temporal and spatial (vertical) patterns of underwater light climate, thermal and chemical characteristics of a little known soda were studied. Parameters of underwater light climate showed light-limited conditions with more marked inter-monthly variations, associated with the accumulation of Arthrospira biomass in the shallow trophogenic zone. Water column conditions indicated superficial thermal stratification (0–3 m depths) with weak temperature gradients and weak mixing pattern. Dissolved oxygen (DO) varied considerably among months, ranging from subsurface supersaturation on certain occasions to persistent deoxygenation of most of the water column on other occasions, with the variations being attributable to the high productivity, high metabolic rates of microbes and weak vertical mixing. Alkalinity, conductivity and pH were generally high with moderate temporal and vertical variations, which were presumably associated with precipitation, evaporation and high algal biomass. In most cases, CO 3 2−:HCO 3 was high (>1), suggesting lower concentration of HCO 3 . Most of the major algal nutrients showed considerable inter-monthly and vertical variations. NO 3 and NH 3 in the euphotic zone were often very low or undetectable while soluble reactive phosphate (SRP) and total phosphorus (TP) were considerably high throughout the study period. The observed dramatic increase in the levels of NH 3 and SRP with depth is attributable to internal loading, which is enhanced by increased microbial activities and largely anoxic water column. The concentration of SiO 2 was remarkably low, which was probably due to organic matter accumulation within the lake that tends to preclude internal loading. In general, the notable temporal and vertical variations in physicochemical parameters, associated chiefly with the lake’s productivity, microbial activity, anoxic water column and meteorological conditions, probably suggest that Lake Chitu is sensitive to perturbations and that any environmental changes occurring in the lake are likely to affect the key planktonic alga ( Arthrospira ) and its ecosystem values.

Benthic macroinvertebrates based new biotic score “ETHbios” for assessing ecological conditions of highland streams and rivers in Ethiopia

Publication date: May 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 52
Author(s): Aschalew L. , Otto Moog
The study describes the development of a macroinvertebrate based biotic score system (ETHbios) for assessing the ecological status of rivers in the Ethiopian highlands. The ETHbios is basically developed on the principle of the BMWP approach (version of the South African Scoring System) but excludes taxa that don’t occur in Ethiopia and includes some of Ethiopian fauna. Macroinvertebrates were collected from 104 sites distributed in a total area about 98,000 square kilometers in the upper Awash, Rift-Valley, Wabi-Shebele and Genale basins. A sensitivity score was assigned to 59 taxa based on guide score, taxon distribution across river quality classes, reference score and autecological knowledge. To define the ranges of the five river quality classes (high, good, moderate, poor and bad), the ETHbios values of sites were correlated with the corresponding ecological status of the sites derived by the Ethiopian Multimetric Index. The validation procedure was done by comparing the ETHbios with selected environmental parameters (conductivity, dissolved oxygen, biological oxygen demand and total phosphorus); the analysis showed significantly high correlations ( r > 0.5; p < 0.05). ETHbios can be considered as rapid, inexpensive but scientifically sound monitoring method that can be used to evaluate the ecological conditions of running waters in the highlands of Ethiopia.

Temporal abiotic variability structures invertebrate communities in agricultural drainage ditches

Publication date: May 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 52
Author(s): Merrin H. Whatley , J. Arie Vonk , Harm G. van der Geest , Wim Admiraal
Abiotic variability is known to structure lotic invertebrate communities, yet its influence on lentic invertebrates is not clear. This study tests the hypothesis that variability of nutrients and macro-ions are structuring invertebrate communities in agricultural drainage ditches. This was determined by investigating invertebrate adaptations to disturbance using insect life-history strategies. Many low-lying agricultural areas contain drainage ditches which potentially provide suitable habitat for aquatic invertebrates. In the province of North Holland (The Netherlands) the extensive network of eutrophic ditches are hydrologically managed, creating seasonal variability of water quality arising from agricultural run-off and the inlet of mineral rich, river derived water. This temporal variability was analysed from monitoring data, collected over a 7 month period (February till August) and covering 84 ditches in three soil regions; sand, clay and peat. Invertebrate diversity was determined as local ( α diversity), regional ( γ diversity) and species-turnover ( β diversity). We ran canonical correspondence analysis and linear mixed models to determine correlations between invertebrate diversity, functional community composition and specific abiotic parameters, including variability (expressed as the Median Absolute Deviation). Invertebrate α diversity was positively correlated to variability in water transparency and negatively correlated to average pH, with the two parameters reflecting a water quality gradient in the environment. Insect life-history strategies expressed adaptations to abiotic variability and harsh (eutrophic) conditions. These adaptations were mainly achieved through good dispersal abilities and developmental trade-offs. The results support measures to reduce influxes of excess nutrients to this network of ditches.

Long-chain n-alkenes in recent sediment of Lake Lugu (SW China) and their ecological implications

Publication date: May 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 52
Author(s): Zhang Yongdong , Su Yaling , Liu Zhengwen , Chen Xiangchao , Yu Jinlei , Di Xiaodan , Jin Miao
Long-chain n -alkenes showing a predominance of n -C 25:1 and n -C 27:1 were detected in recent sediment of Lake Lugu, an oligotrophic alpine lake in Yunnan Province, SW China. The abundances of n -C 25:1 and n -C 27:1 alkenes varied considerably in the sediment core, most obviously in showing higher values during the period of 1821–1982, followed by a significant decrease between 1982 and 2012. Such variations were similar to those of long-chain 1,15-alkyl diols, biomarkers of eustigmatophytes, and a significant correlation was observed between n -C 25:1 (or n -C 27:1 ) alkene and C 32 1,15-alkyl diol in the sediment core. This correlation and the fact that long-chain n -alkenes in some eustigmatophytes (e.g., Nannochloropsis sp.) were dominated by C 25 and C 27 compounds indicates that eustigmatophytes were the most likely contributor of the long-chain n -alkenes (especially the n -C 25:1 and n -C 27:1 alkenes) in Lake Lugu sediment. Chlorophytes, on the other hand, cannot be excluded as a possible contributor of the long-chain n -alkenes because these algae are common in Lake Lugu and they are known to biosynthesize n -C 27:1 alkene. Productivities for some species of eustigmatophytes and chlorophytes considerably decreased when the lake water was heavily influenced by catchment soil erosion and anthropogenic sewage inputs.

Management options of invasive Elodea nuttallii and Elodea canadensis

Publication date: Available online 10 February 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Andreas Zehnsdorf , Andreas Hussner , Frank Eismann , Helmut Rönicke , Arnulf Melzer
Elodea nuttallii and Elodea canadensis , two invasive submerged and rooted aquatic macrophyte species, are receiving increasing attention for their rapid and lasting invasion of many freshwater habitats throughout Europe, Asia and Australia. This review summarizes the present scientific knowledge about means of controlling Elodea nuttallii and Elodea canadensis within of aquatic weed management programs. Both species exhibit high growth rates with a high tolerance to wide ranges of environmental conditions, low vulnerability to grazing and other stress factors, high distribution and reproduction potential, and relatively high resistance to common conventional aquatic weed management procedures. Possibilities for the further use of harvested Elodea biomass are presented and novel approaches to the improvement of the monitoring and management of Elodea plagues are discussed.

Fine sediment deposition affects biodiversity and density of benthic macroinvertebrates: A case study in the freshwater pearl mussel river Waldaist (Upper Austria)

Publication date: Available online 29 December 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): P. Leitner , C. Hauer , T. Ofenböck , F. Pletterbauer , A. Schmidt-Kloiber , W. Graf
Fine sediment deposition in stream beds frequently generated by certain land use practices has become an increasing stressor for rivers throughout the world. In this study, the role of fine sediment deposition and its impact on the benthic macro-invertebrate assemblages was investigated in a low mountain freshwater pearl mussel stream, the Waldaist. Communities of unaffected sites and sites under high fine sediment deposition were compared. Distinct reactions of benthic assemblages in fine gravelly habitats were ascertained demonstrating a severe but still underestimated threat for invertebrate biodiversity.

Influence of nitrate and dissolved organic carbon loading on the interaction of Microcystis aeruginosa and heterotrophic bacteria from hyper-eutrophic lake (Taihu Lake, China)

Publication date: Available online 20 January 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Du Jingjing , Ma Xu , Pu Gaozhong , Kong Xiangshi , Akbar Siddiq , Jia Yanyan , Tian Xingjun
To investigate the interaction between cyanobacteria and heterotrophic bacteria under gradients of glucose and nitrate, a cyanobacterial strain of Microcystis aeruginosa was grown in microcosms with and without a freshwater bacterial mixture, which was collected from Lake Taihu. Concentrations of glucose (1350, 975, 600, 300, 150, and 37.5 μmol C L−1) and nitrate (150, 300, and 9000 μmol N L−1) were used in a range of combinations giving 9 different treatments of glucose:nitrate. In the microcosm without the bacterial mixture, M . aeruginosa abundance gradually increased with days in all treatments. However, M. aeruginosa had much lower density in some treatments with the bacterial mixture. The difference in M. aeruginosa growth could be explained by competition with bacteria in the cultures in which these were added. The abundance of M. aeruginosa and bacteria when grown together was nearly equal and the number of the bacterial species was highest in the treatment with 300 μmol C L−1 and 150 μmol N L−1. Our results suggest that at this glucose:nitrate ratio M . aeruginosa and the bacterial mixture maintain a balance, and bacteria maintain diversity. In conclusion, we propose that dissolved organic carbon and nitrate availability fundamentally affects the structure as well as stoichiometry of pelagic associations.

Spatial Arrangement and Metrics of Freshwater Coastal Rock Pools Applied to Amphibian Conservation

Publication date: Available online 17 January 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Alexander T. Egan , Leonard C. Ferringtona Jr. , Toben Lafrançois , Mark B. Edlund , Jenna McCullougha
Coastal habitats are an ecotone between aquatic and terrestrial ecosystems. Depressions on volcanic bedrock shores of Lake Superior form small pool habitats that are influenced to various degrees by their spatial context and that relate to differences in mechanisms of disturbance. A total of 71,931 coastal pools were mapped and measured, and amphibian occupants were identified along 48 km of shoreline at Isle Royale National Park, where coastal rock pool habitats were abundant. Generally, mean depth of pools was 0.11 m, with a mean surface area of 0.6 m2, although maximum measurements were 1.5 m and 378 m2, respectively. Three strongly defined zones occurred, with bedrock near the lake having a low slope and more numerous, smaller, and shallower pools; bedrock near the forest edge had a steeper slope and fewer, larger, and deeper pools; and a median zone occurring between. A single offshore location, Passage Island, had nearly 63% of all pool abundance. Two amphibian species were typical of coastal pools, the chorus frog ( Pseudacris triseriata ) and blue-spotted salamander ( Ambystoma laterale ), while spring peeper ( Pseudacris crucifer ) was uncommon and probably incidental to coastal habitats. These three species were significantly more abundant in mid-shore pools. Four other amphibian species were only rarely detected. Both coastal habitat density and chorus frog abundance were highest at localities directly adjacent to an international shipping lane. As a result of intriguing spatial distributions and potential for impacts from coastal pollution, chorus frog in particular reveals that coastal ecology can be unique from inland contexts and have important management implications at the land-water interface.

Determining useful benchmarks for the bioassessment of highly disturbed areas based on diatoms

Publication date: Available online 13 January 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Carmen L. Elias , Ana R. Calapez , Salomé F.P. Almeida , Maria J. Feio
Modern ecological assessments of running waters are based on the a priori definition of ecological benchmarks, given by reference-quality sites. Such benchmarks are established at the level of ecoregions, typologies, or site. Yet, in highly disturbed regions, such as coastal areas of European countries, the assessment of streams’ water quality based on the reference condition concept is very difficult, due to the lack of undisturbed sites. Among others, the reduced number of reference sites may have as a consequence the definition of imprecise ecological benchmarks. Here we tested the hypotheses that 1) the increase in the number of potential reference sites 2) the definition of more precise abiotic thresholds using the Least Disturbed Condition approach (LDC), and 3) the use of diatom assemblages, as the most ubiquitous element in lowland areas, would result in refinement and eventual sub-division of existing river types of a highly disturbed area, such as the Portuguese centre-western region. For this purpose, abiotic data characterising natural conditions of 55 sites from a littoral highly disturbed region were used in a hierarchical classification analysis that revealed the existence of three different sub-groups. In addition, a three-step approach was used to define thresholds for the pressure variables in LDC. Based on these new thresholds, sites in LDC were selected. A hierarchical classification performed to the LDC diatom spring assemblages revealed the existence of two sub-groups, concordant with two of the abiotic sub-groups. Several species contributed to the dissimilarity between the two sub-groups (e.g., Achnanthidium minutissimum and Karayevia oblongella ). Differences between the sub-groups were also found in the trait proportions of stalked species. New benchmark values for these two sub-groups, based on the scores of the official diatom index, the Indice de Polluo-sensibilité Spécifique (IPS), were different from the previous reference value used. Yet, no biological benchmark values were established for one of the groups due to the absence of sites in the LDC. Our study suggests that streambed substrate is an important characterisation variable in the river type definition and highlights that, in spite of the potential refinement in reference conditions and typology obtained, an alternative approach that does not require the use of reference sites should be explored in the future.

Live bait capture and crayfish trapping as potential vectors for freshwater invasive fauna

Publication date: Available online 7 January 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Filipe Banha , Pedro Manuel Anastácio
Fishing activities strongly contribute to biological invasions in freshwaters. The purpose of this study was to investigate the potential risks of live bait capture using dip nets and of crayfish trapping as vectors for invasive freshwater macrofauna dispersal. In the Tagus river basin (Portugal), where both activities are common, we evaluated the probability of capture and the electivity of the local aquatic macrofauna according to the method used. During the compulsory removal of the invasive species captured we also quantified fish desiccation survival capacities. We found, for both vectors, that the species exhibiting the highest probability of capture and the highest electivity were invasive, respectively Gambusia holbrooki and Crangonyx pseudogracilis with the dip net, Procambarus clarkii and several invasive species with special relevance for Ameiurus melas with the crayfish trapping. Moreover, the desiccation survival capacities, of all invasive fishes analyzed, are compatible with long distance dispersal out of water, with special relevance to G. holbrooki. This study demonstrates that fishing activities contribute to long-distance dispersal of invasive fauna. Therefore, according to our findings, it is important to update the fishing regulation and simultaneously to raise fishermen awareness of this problem.

Conservation of the freshwater pearl mussel (Margaritifera margaritifera) in the river Rede, UK: Identification of instream indicators for CAtchment-scale issues

Publication date: Available online 5 January 2015
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Marie-Pierre Gosselin
The freshwater pearl mussel ( Margaritifera margaritifera ) is declining throughout its entire range. On the river Rede, North-East England, the population has been equally declining and shows no apparent recruitment. The study presented here aimed at characterizing water quality and habitat conditions for pearl mussels to identify possible indicators of pressures on the population and inform a restoration and conservation strategy. Water quality monitoring revealed levels of turbidity and suspended sediments to be above the limit set for functional pearl mussel rivers. Substrate sampling revealed silt was present at all sites. A loss of redox potential between the water column and the substrate occurred at all sites, indicating non suitable conditions for juvenile pearl mussels. These investigations suggest that fine sediment input in the river could be one of the factors preventing the development and survival of juvenile mussels while adults face water quality largely affected by high turbidity and high phosphate load. Restoration strategy for the Rede pearl mussel population should focus mainly on limiting sediment and nutrient input in the river throughout the catchment in order to improve habitat for juvenile pearl mussels. This work highlights the need for a catchment based approach in order to succeed in the conservation of a fragile species.

Fine sediment deposition affects biodiversity and density of benthic macroinvertebrates: 1: A case study in the freshwater pearl mussel river Waldaist (Upper Austria)

Publication date: Available online 29 December 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): P. Leitner , C. Hauer , T. Ofenböck , F. Pletterbauer , A. Schmidt-Kloiber , W. Graf
Fine sediment deposition in stream beds frequently generated by certain land use practices has become an increasing stressor for rivers throughout the world. In this study, the role of fine sediment deposition and its impact on the benthic macro-invertebrate assemblages was investigated in a low mountain freshwater pearl mussel stream, the Waldaist. Communities of unaffected sites and sites under high fine sediment deposition were compared. Distinct reactions of benthic assemblages in fine gravelly habitats were ascertained demonstrating a severe but still underestimated threat for invertebrate biodiversity.

Natural variation of macrophyte vegetation of lowland streams at the regional level

Publication date: Available online 27 December 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Gerhard Wiegleb , Wolfgang Herr , Bärbel Zander , Udo Bröring , Holger Brux , Klaus van de Weyer
In the present study, we present a synopsis of two macrophyte surveys of physiographic units in northwest Germany carried out over one decade. Data were used to test a set of hypotheses on macrophyte distribution at the regional level. Rank-frequency curves resembled the broken stick model. Twenty-one species of the 59 most frequent species occurred at high frequencies above 15 percent. Helophytes made up a high percentage (12 of 21) of the frequent species. Phalaris arundinacea was the most frequent species in both sampling periods. Most species showed no considerable change in frequency over time, among them the core hydrophytes. Spatial variation of species frequencies among physiographical units showed a unimodal distribution in relation to frequency. Spatial variation of frequencies of functional groups was significantly lower. Most uneven distribution among physiographical units was found in cryptogams. DCA ordinations of physiographical units showed a spatial gradient from alluvial plains to higher grounds units, which remained constant over time. CCA ordination of physiographical units in relation to environmental parameters identified two main axes, an altitudinal gradient and an alkalinity gradient. Species composition of units corresponded to the main landscape pattern of alluvial plains, glacial lowlands, and higher grounds on Mesozoic rock. Species diversity showed a complex behavior. Diverse units were found both in alluvial plains and glacial lowlands of intermediate elevation. The study may help defining regionally differentiated reference states for stream management, benchmarking indicator scores of species and avoiding application of assessment methods outside their range of applicability.

Influence of host fish age on a mussel parasite differs among rivers: Implications for conservation

Publication date: Available online 24 November 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): E. Martin Österling
Unionoid mussels are obligate parasites on one or more fish species. The objective was to compare growth and survival of encysted mussel larvae of the freshwater pearl mussel ( Margaritifera margaritifera ) on young-of-the-year (YOY) versus one-year old brown trout ( Salmo trutta ). YOY and one-year old trout from the Brattefors and Lärje Rivers, Sweden, were infested with mussel larvae from their home river. The mass-normalized encystment abundance was higher on YOY trout than on one-year old trout. The proportional decrease in mass-normalized encystment abundance was larger on YOY brown trout from the Brattefors River than on YOY brown trout from the Lärje River. Encystment per individual fish was higher on YOY trout than on one-year old trout from the Brattefors River, whereas this relationship was reversed for trout from the Lärje River. Larval growth was higher on YOY trout than on one-year old trout. There was a larger difference in larval growth between YOY trout and one-year old trout from the Brattefors River than on the brown trout from the Lärje River. The ability to use both YOY and older fish, such as in the Lärje River, may increase the reproduction potential of mussel populations, compared to a reduced ability to use more than one year class, such as in the Brattefors River. This may also affect the dispersal of mussels, as older brown trout often move and migrate to a higher degree within and between rivers. The dispersal potential of mussels may therefore be relatively high in the Lärje River, but low in the Brattefors River. In rivers where the mussels have to rely on YOY brown trout, it could be worth facilitating passage through migration obstacles for YOY brown trout. Infested YOY brown trout could be artificially re-distributed within rivers, to places with former mussel distributions. It could also be worth testing the suitability of brown trout of different age classes when starting breeding programs.

The status of freshwater pearl mussel in the Czech Republic: several successfully rejuvenated populations but the absence of natural reproduction

Publication date: Available online 24 November 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Ondřej P. Simon , Ivana Vaníčková , Michal Bílý , Karel Douda , Hana Patzenhauerová , Jaroslav Hruška , Alena Peltánová
The freshwater pearl mussel was historically abundant in many streams and rivers in the Elbe, Oder and Danube Basins in the Czech Republic, Central Europe. By the 21st century, the mussels had become extinct in the lower and middle altitudes, and current populations are only present near the upper limit of their natural range. The current population of this mussel is estimated to be only 1% of the historical abundance. The population decline was related to the negative impacts of pollution from industry, intense agriculture, forestry and sewage water. The freshwater pearl mussel habitat has also been impacted by watercourse regulations and has been fragmented by dams and weirs. All of these impacts have resulted in failure of the reproductive cycle; the last significant cohort of juveniles settled approximately 30-40 years ago. Therefore, this species is considered critically endangered, and an action plan was developed to conserve the populations in the Czech Republic. Special measures were conducted between 1984 and 2005 to improve the age structure of elderly populations. Fish infected with millions of glochidia were released in two locations, and over 50,000 captive-bred juveniles that were three to five years old were released in 7 locations. Only the latter approach resulted in a small number of subadults that gradually emerged from the substratum to the bottom surface, as confirmed by monitoring efforts. Despite simultaneous efforts to restore mussel habitat over the last 25 years, natural reproduction still does not occur in the Czech Republic. Therefore, complete restoration of oligotrophic streams is the key to the future presence and natural reproduction of freshwater pearl mussels in the Czech Republic.

Aquatic prey subsidies to riparian spiders in a stream with different land use types

Publication date: March 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 51
Author(s): Bonny Krell , Nina Röder , Moritz Link , René Gergs , Martin H. Entling , Ralf B. Schäfer
Land use related habitat degradation in freshwater ecosystems has considerably increased over the past decades, resulting in effects on the aquatic and the riparian communities. Previous studies, mainly in undisturbed systems, have shown that aquatic emergent insects contribute substantially to the diet of riparian predators. To evaluate the effect of land use on aquatic prey subsidies of riparian spiders, we performed a longitudinal study from June to August 2012 along a first order stream (Rhineland-Palatinate, Germany) covering three land use types: forest, meadow and vineyard. We determined the contribution of aquatic and terrestrial resources to the diet of web-weaving (Tetragnathidae spp.) and ground-dwelling ( Pardosa sp.) riparian spiders using stable isotope analyses of aquatic emergent insects and terrestrial arthropods. The contribution of aquatic and terrestrial sources differed between Tetragnathidae spp. and Pardosa sp. as well as among land use types. Tetragnathidae spp. consumed 80–100% of aquatic insects in the meadows and 45–65% in the forest and vineyards. Pardosa sp. consumed 5–15% of aquatic insects in the forest, whereas the proportions of aquatic and terrestrial sources were approximately 50% in the meadow and vineyard. Thus, aquatic emergent insects are an important subsidy to riparian spiders and land use is likely to affect the proportion of aquatic sources in the spider diet.

Influence of host fish (Salmo trutta) age on a mussel (Margaritifera margaritifera) parasite differs among rivers: Implications for conservation

Publication date: Available online 24 November 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): E. Martin Österling
Unionoid mussels are obligate parasites on one or more fish species. The objective was to compare growth and survival of encysted mussel larvae of the freshwater pearl mussel ( Margaritifera margaritifera ) on young-of-the-year (YOY) versus one-year old brown trout ( Salmo trutta ). YOY and one-year old trout from the Brattefors and Lärje Rivers, Sweden, were infested with mussel larvae from their home river. Larval encystment was higher on YOY trout than on one-year old trout. The proportional decrease in mass-normalized encystment abundance was larger on YOY brown trout from the Brattefors River than on YOY brown trout from the Lärje River. Encystment per individual fish was higher on YOY trout than on one-year old trout from the Brattefors River, whereas this relationship was reversed for trout from the Lärje River. Larval growth was higher on YOY trout than on one-year old trout. There was a larger difference in larval growth between YOY trout and one-year old trout from the Brattefors River than on the brown trout from the Lärje River. The ability to use both YOY and older fish, such as in the Lärje River, may increase the reproduction potential of mussel populations, compared to a reduced ability to use more than one year class, such as in the Brattefors River. This may also affect the dispersal of mussels, as older brown trout often move and migrate to a higher degree within and between rivers. The dispersal potential of mussels may therefore be relatively high in the Lärje River, but low in the Brattefors River. In rivers where the mussels have to rely on YOY brown trout, it could be worth facilitating passage through migration obstacles for YOY brown trout. Infested YOY brown trout could be artificially re-distributed within rivers, to places with former mussel distributions. It could also be worth testing the suitability of brown trout of different age classes when starting breeding programs.

Contrasting decay rates of freshwater bivalves’ shells: Aquatic versus terrestrial habitats

Publication date: March 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 51
Author(s): M.I. Ilarri , A.T. Souza , R. Sousa
Freshwater flow regimes are particularly vulnerable to global climate change with changes to the volume and regime of water contributing to global declines in freshwater biodiversity. Droughts or floods can cause massive mortalities of freshwater bivalves, facilitating the accumulation of shells in the aquatic but also in adjacent terrestrial habitats. In order to fully understand the long term impact of these massive mortality events, it is important to assess how bivalve shells persist in the environment. Given that, the present study aimed at studying the shell decays of four different bivalve species ( Anodonta anatina , Corbicula fluminea , Potomida littoralis and Unio delphinus ) in aquatic (i.e. river) versus terrestrial (i.e. sand soil) habitats. Shell decay rates were significantly different among species and habitats. In the aquatic habitat the shell decay rates varied among species, with the native species A . anatina , which have the largest and thinnest shell, showing the highest decay rate. Alternatively, in the terrestrial habitat the shell decay rates were more even among species and not related to a particular shell feature or morphology, with the native U . delphinus showing the fastest decay. The shell decay rates were 6 to 12 times higher in aquatic than in the terrestrial habitat. These results suggest that bivalve shells can persist for long periods of time on both habitats (but mainly in terrestrial), which may perhaps trigger significant changes on the ecosystem structure and functioning.

Small leaf breakdown in a Savannah headwater stream

Publication date: Available online 11 November 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Elisa Araújo Cunha Carvalho Alvim , Adriana de Oliveira Medeiros , Renan Souza Rezende , José Francisco Gonçalves Jr.
The chemical nature and nutritional quality of leaves influence microbial colonization, microbial activity and consequently leaf breakdown rates. In the present study, we compared the decomposition of Baccharis concinna and Baccharis dracunculifolia leaves and the influence of leaf quality on the microbial activity during the decomposition process. This investigation was conducted in a Brazilian savanna headwater stream with a riparian zone composed predominantly of herbaceous and shrubs. The breakdown coefficient was higher in B. dracunculifolia than in B. concinna ; for both species, increases in leaf mass were observed after the 60th day. The secondary compounds were quickly leached in the first seven days, but the structural compounds persisted longer and served as the main carbon source for the detritus-associated microorganisms. The highest values of ergosterol were observed in the final stages of leaf breakdown and indicated the difficulty of colonization on the detritus; these values were related to the increase in leaf mass. The ATP content increased without corresponding increase in ergosterol content, suggesting a biofilm formation during leaf breakdown. These results indicated that the total microbial biomass can assimilate organic compounds released from detritus by the enzymatic action of fungi, demonstrating the importance of this group for releasing the energy stored in small leaves.

Changes in the epipelic diatom assemblage in nutrient rich streams due to the variations of simultaneous stressors

Publication date: March 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 51
Author(s): Joaquín Cochero , Magdalena Licursi , Nora Gómez
Benthic diatoms are often used for assessing environmental conditions, such as water quality and habitat conditions in stream and river systems. Although laboratory experiments have shown that each diatom species have different levels of tolerance to different stressors, few studies have been conducted in laboratory settings that analyze the responses of the diatom assemblage to the effects of multiple simultaneous variables. The aim of this study was to evaluate some structural responses (such as species composition and diversity) of the diatom assemblage on a short time scale to the effects of the simultaneous increase in four variables that are directly linked to the environmental changes affecting the Pampean streams: turbidity, nutrients (phosphorous and nitrogen), water velocity and temperature. To this end we conducted a five-week laboratory experiment using artificial channels where we simulated two environmental conditions (LOW and HIGH) employing epipelic biofilm from a mesotrophic stream. The results obtained in the experiment show that the structure of the diatom assemblage in the epipelic biofilm is affected by the simultaneous modification of temperature, water velocity, nutrient concentration and turbidity. These modifications in the assemblage included moderate decreases in diversity, small decreases in the proportion of species sensitive to eutrophication and saprobity, moderate increases in the IDP (Pampean Diatom Index) values and moderate changes in the percentages of the stalked growth-forms. The relative abundance of species such as Luticola mutica, Navicula cryptocephala and Navicula lanceolata were negatively affected by both treatments; other species such as Planothidium lanceolatum, Caloneis bacillum, Encyonema minutum, Humidophila contenta, Luticola kotschyi, Nitzschia amphibia, Navicula veneta, Pinnularia subcapitata var . subcapitata were positively affected by the HIGH treatment; and Nitzschia fonticola was positively affected by both treatments. The results suggest that, in the very short term of the bioassay conducted, the diatom assemblage can modify its structure to respond in a sensitive manner to the abrupt changes in multiple physical–chemical variables.

Fish distribution patterns and habitat availability in lakes Moreno Este and Moreno Oeste, Patagonia, Argentina

Publication date: November 2014
Source:Limnologica – Ecology and Management of Inland Waters, Volume 49
Author(s): Magalí Rechencq , Pablo Horacio Vigliano , Patricio Jorge Macchi , Gustavo Enrique Lippolt
Andean Patagonian lakes are ultraoligotrophic and deep, have simple food webs and low fish diversity and abundance. In this work the distributional abundance data of fish was studied in two interconnected Andean Patagonian lakes with varying proportions of contrasting habitat types. Hydroacoustic data (120 kHz) were used to analyze fish abundance and habitat use during the mixis and stratification periods. Three types of habitat (near shore, surface pelagic and deep pelagic) and two groups of fish, based on size (Big Fish >12 cm total length and Fish Larvae and Small Fish <12 cm total length) were defined. The distribution of both fish groups in these lakes revealed differences in habitat use for each lake and period. Fish group abundance was related to the availability of habitat types, according to the morphology of each lake. The Big Fish group showed preference for the near shore habitat during lake stratification and always appeared as individual targets. The Fish Larvae and Small Fish group used mainly the pelagic habitat during mixis, where they formed dense sound scattering layers. However, during lake stratification many individual targets from this group were found both in pelagic and near shore habitats, which would seem to indicate a change in distributional behavior. This is possibly associated with niche changes in the Galaxiids ( Galaxias spp), a key component of Northern Patagonian lake food webs. Lakes like Moreno Oeste, which are morphologically and structurally more complex, could have more diverse fish ensembles with higher abundances. In contrast, lakes of simple morphology with low development of near shore habitats and ample deep zones, like Lake Moreno Este, could present lower Big Fish abundance. The contrasting habitat availability between lakes accounts for the abundances and distribution patterns of each fish group. While in these lakes fish assemblage species composition could depends on the environmental filter, the particular structure of a fish assemblage in terms of the proportional abundances of species depends on proportional habitat type availability. We can speculate that in Andean Patagonian lakes Galaxiids mediate a habitat coupling process critical for the transfer of energy and matter in oligotrophic lakes. We may also consider that the Small Puyen in this type of lake is a keystone prey species that relieves predation pressure on other potential prey. The existence of deep pelagic habitats in numerous deep lakes in the Northern Patagonian Andean region provides not only daytime refuge for Galaxiids, which allows them to maintain their high numbers in the lakes, but could also, in the long term, act as a Galaxiid source for other water bodies.

Experimental assessment of predation by native and exotic fish on stream invertebrates in Northern Patagonia

Publication date: March 2015
Source:Limnologica – Ecology and Management of Inland Waters, Volume 51
Author(s): Domink Geray , Ricardo Albariño , Daniela Milano
During the last decades invasive species became a matter of concern all over the world. Established salmonid populations make sport fishery in Patagonia one of the top in the world, but there is increasing evidence that these populations have negative impacts on native ecosystems. Predation rates and feeding preferences of native catfish Hatcheria macraei and invasive trout Oncorhynchus mykiss were compared by exposing three stream benthic invertebrate species with contrasting ecological roles to direct predation. Secondly, feeding and escaping behaviours of the mayfly Meridialaris chiloeensis belonging to either non-naive or naive populations to predators were investigated in the presence of predation chemical cues, i.e. non direct predator access. Total predation by trout was 2–3 times higher than by native catfish. Trout had clear prey preferences while catfish changed its preferences with shifting prey composition. Invertebrate species showed different responses to predation by native and exotic fish due to the different strategies of fish and invertebrates which resulted from the combination of predator efficiency and prey vulnerability. Feeding activity of non-naive nymphs was significantly lower than that of naive nymphs. In addition, mayfly nymphs from both populations showed higher emigration rates in presence of trout chemical cues than in presence of catfish cues or in fishless treatment. Consequently, the reduced feeding activity observed in non-naive mayflies exposed to rainbow trout cues resulted from their inactivity in channels, as both nymph populations had similar emigration rates. Due to high predation rates, prey preferences (i.e. high potential to exploit prey resources) and induced strong predation avoidance behaviour of prey, invasive trout may have a stronger influence on the abundance and species composition of native macroinvertebrates than native catfish. In just about one century, invertebrate species such as the ubiquitous M. chiloeensis show behavioural adaptations to this exotic predator.

Impact of deforestation on pearl mussel habitats in the Russian section of the Baltic Sea basin

Publication date: Available online 1 November 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Igor Popov
Changes in the vegetation cover associated with intensive forest extermination may have a strong effect on the riverine environment, including the chances of survival for bivalve mollusc populations in small streams and rivers. In order to check this hypothesis, drainage area properties of the rivers with extinct and existing pearl mussel populations in the Russian section of the Baltic Sea basin were compared. Preservation of forest vegetation along the river banks of the studied rivers was correlated with the presence of pearl mussel populations. Traditional agriculture turned out to be, in some cases, more harmful for river ecosystems than urbanization and industrialization.

New data on the zoogeography of Aphanius sophiae (Teleostei: Cyprinodontidae) in the Central Zagros (Southwest Iran)

Publication date: Available online 12 December 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Zeinab Gholami , Hamid Reza Esmaeili , Bettina Reichenbacher
The clade of the Iranian freshwater Aphanius species from endorheic and exorheic drainage basins contains three subclades, of which the A. sophiae subclade with seven species is the most specious one. Recently, two previously not known populations of Aphanius were discovered in two isolated basins; one in the Arjan Wetland (Helleh subbasin), and the other in the Semirom spring (Karun Basin), both are located in the Central Zagros Mountains (SW Iran). The objective of this study is to investigate their taxonomic status, to elucidate their phylogenetic relationships and to contribute to future conservation strategies and habitat management of the freshwater species of Aphanius in Iran. Methods include analysis of genetic data based on mtDNA ( cyt b ), combined with meristics, morphometrics, scale sizes (J-indices) and otolith data. The results based on cyt b clearly indicate that two species are present in the Arjan Wetland, one is closely related to A. sophiae (currently thought to be restricted to the Kor Basin), the other represents A. shirini (previously only known from its type locality Paselari spring). However, significant phenotypic differences are not present between these two species. The second population from the Semirom spring is sister to A. sophiae (Kor Basin) according to cyt b data, but differs significantly from this species with regard to the phenotype. The presence of A. shirini in the Arjan Wetland is most likely be explained by man-made introduction because of the recent droughts. The similarity of the two species present in the Arjan Wetland may be due to phenotypic plasticity, but also hybridization could have played a role. The isolation of populations of A. sophiae is discussed in the context of the active geological history and climate change, and it is likely that their divergence happened in the Early or Middle Holocene (c. 11,700–4,000 y. ago). The presence of A. sophiae in the Helleh subbasin and Karun Basin extends the currently known zoogeographic range of this species, which previously has only been reported from the Kor Basin. Such knowledge is important for future conservation strategies and habitat management.

Human waterborne protozoan parasites in freshwater bivalves (Anodonta anatina and Unio tumidus) as potential indicators of fecal pollution in urban reservoir

Publication date: Available online 6 December 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Anna Słodkowicz-Kowalska , Anna C. Majewska , Piotr Rzymski , Łukasz Skrzypczak , Anna Werner
The presence of environmentally robust dispersive stages of intestinal protozoan parasites in waters represents an important public health threat since these pathogens have caused numerous outbreaks related to either drinking or recreational waters. The purpose of this study was to evaluate the presence of Cryptosporidium oocysts, Giardia and Blastocystis cysts, and microsporidian spores in mussels collected from municipal reservoir, Lake Malta (Poland, Europe). Two species of freshwater bivalves ( Anodonta anatina and Unio tumidus ) were tested for the enteropathogens. A direct wet smear and smears stained with chromotrope 2R, Ziehl-Neelsen and iron hematoxylin made from each pellet of the hemolymph, gills and gastrointestinal homogenates of mussels were examined microscopically. In the study the immunofluorescence antibody test kit MERIFLUOR Cryptosporidium/Giardia was also used for all bivalve samples. None of investigated parasites were found in U. tumidus . In A. anatina , Cryptosporidium oocysts and Blastocystis cysts were detected in 15.4 and 5.1% of mussel samples, respectively. The present results indicate contamination of Lake Malta with Cryptosporidium and Blastocystis , which is important from the point of view of public health threats because of different human uses of studied reservoir.

A new fish-based multi-metric assessment index for cyprinid streams in the Iranian Caspian Sea Basin

Publication date: Available online 1 December 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Hossein Mostafavi , Rafaela Schinegger , Andreas Melcher , Karl Moder , Carina Mielach , Stefan Schmutz
A major issue for water resource management is the assessment of environmental degradation of lotic ecosystems. The overall aim of this study is to develop a multi-metric fish index for the cyprinid streams of the Caspian Sea Basin (MMICS) in Iran. As species diversity and composition as well as population structure in the studied streams are different to other regions, there is a substantial need to develop a new fish index. We sampled fish and environmental data of 102 sites in medium sized streams. We analysed human pressures at different spatial scales and determined applicable fish metrics showing a response to human pressures. In total, five structural and functional types of metrics (i.e. biodiversity, habitat, reproduction, trophic level and water quality sensitivity) were considered. In addition, we used 29 criteria describing major anthropogenic human pressures at sampling sites and generated a regional pressure index (RPI) that accounted for potential effects of multiple human pressures. For the MMICS development, we first defined reference sites (least disturbed) and secondly quantified differences of fish metrics between reference and impaired sites. We used a Generalized Linear Model (GLM) to describe metric responses to natural environmental differences in least disturbed conditions. By including impaired sites, the residual distributions of these models described the response range of each metric to human pressures, independently of natural environmental influence. Finally, seven fish metrics showed the best ability to discriminate between impaired and reference sites. The multi-metric fish index performed well in discriminating human pressure classes, giving a significant negative linear response to a gradient of the RPI. These methods can be used for further development of a standardised monitoring tool to assess the ecological status and trends in biological condition for streams of the whole country, considering its complex and diverse geology and climate.

Test of the host fish species of a unionoid mussel: A comparison between natural and artificial encystment

Publication date: Available online 27 November 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): E. Martin Österling , Niklas Wengström
Many of the unionoid mussel species are threatened, and to be able to develop strategies for effective conservation, one of the needs is to distinguish host fish species from non-host fish species using reliable methods. Margaritifera margaritifera lives as a parasite on brown trout ( Salmo trutta ) and/or Atlantic salmon ( Salmo salar ). The aim was to compare the reliability of two methods measuring the host specificity of M. margaritifera in two rivers that flow out into Skagerrak in the Atlantic Ocean. A second aim was to compare the time- and cost-efficiency of the two methods. The methods were (1) natural encystment abundances on fish in their native streams using electrofishing, and (2) encystment abundances from controlled artificial infestation in aquaria, on fish that were sacrificed. In both rivers, young-of-the-year (YOY), but not older brown trout, were naturally infested with relatively low loads of glochidia larvae, while the Atlantic salmon was not infested at all. When using artificial infestation, both YOY and older brown had encysted glochidia larvae on their gills, while glochidia larvae were not able to develop in Atlantic salmon at all. Here, the encystment was higher on the brown trout from the Lärje River, and older brown trout from the Lärje River did not seem to have as strong immunity response compared to older brown trout from the Brattefors River. In summary, brown trout is the only host fish for M. margaritifera in these rivers. Both methods can be used to discriminate between host fish species, but the method measuring natural encystment seems most time- and cost-efficient. In addition, natural encystment can be measured using a non-destructive photo-method, and is therefore suggested to be used when discriminating between host fish species for M. margaritifera .

Sustainable catchment restoration for reintroduction of captive bred freshwater pearl mussels Margaritifera margaritifera

Publication date: Available online 25 November 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Mark Horton , Alan Keys , Lisa Kirkwood , Francis Mitchell , Rebecca Kyle , Dai Roberts
The Ballinderry River, Co. Tyrone (SAC), is one of only six rivers in Northern Ireland that still supports a population of the globally endangered freshwater pearl mussel, Margaritifera margaritifera . Fewer than 1000 individuals still exist in the river; without intervention it is predicted the Ballinderry pearl mussel will be extinct by 2098. This paper aims to identify key catchment pressures on remaining mussel stocks and prioritise tributaries within the catchment for remediation work to ensure effective targeting of limited resources. A combination of redox assessment, river surveys and SCIMAP modelling was used to rank tributaries, taking into consideration their size and proximity to the main mussel population at the “sanctuary site”. Diffuse and point sources of sediment were identified within the prioritised catchment. The Tulnacross tributary was selected as the highest priority tributary and has been used in a pilot remediation study. A number of different hard and soft engineering techniques have been used for remediation as well as replacing cattle drinkers with pasture pumps and fencing alongside the river. Initial observations suggest river substrate is cleaner. This study is an example of how to tackle problems within a large-scale catchment with limited resources with participation of local stakeholders and riparian landowners.

Review of Hydro-morphological management Criteria on a river basin scale For preservAtion and restoration of freshwater pearl mussel habitats

Publication date: Available online 25 November 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): C. Hauer
Increases in the fine sediment supply and fine sediment deposits have been highlighted as one of the main pressures affecting the ongoing degradation of Freshwater Pearl Mussel Margaritifera margaritifera (L.) (FWPM) habitats. Those impacts, however, have been mostly investigated on a local scale without considering catchment scale boundaries that might decisively influence sediment production over the short to the long term. Hence, the aim of this review study was to reveal the importance of scaling sedimentological and morphological processes especially in terms of the preservation and restoration of freshwater pearl mussel habitats. The focus was on the Austrian territory, where the crystalline catchments of the Mühl- and Waldviertel exhibited site specific characteristics of sediment production and sediment transport. The importance of the variability in the grain size distribution as well as the variability in river morphology for evaluating freshwater pearl mussel habitats are reviewed, especially in terms of the implementation of possible mitigation measures. For evaluating FWPM rivers, a revised sedimentary link concept is discussed, considering the main driving processes to be an increase in the fine sediment supply from tributaries. As possible mitigation measures, structural measures, such as transversal obstructions or boulder placement, and non-structural measures, such as initiation of the overbank deposition of fines and land use changes, are presented. The validation of mitigation is discussed based on monitoring the results of boulder placements and overbank deposits of tributaries after a 10-year flood in 2013. Based on a review of habitat needs of FWPM and the variability of the abiotic environment, it could be concluded that it is necessary to consider the catchment scale approach in the preservation and restoration of freshwater pearl mussel rivers, linked from the headwater tributaries to the selected habitats over the mid to the long term.

Do installed stream logjams change benthic community structure?

Publication date: November 2014
Source:Limnologica – Ecology and Management of Inland Waters, Volume 49
Author(s): Todd Wellnitz , Se Yeon Kim , Eric Merten
Installed logjams constructed of wood are commonly used in stream restoration projects to provide habitat for lotic organisms. Macroinvertebrate densities are known to increase on logjam surfaces; however, less is known about the influence logjams have on benthic organisms inhabiting the surrounding streambed. To examine this, we conducted a before-after-control-impact (BACI) study in a stream in northern Minnesota, USA, to determine how an installed logjam affected the richness and abundance of three insect orders commonly used in biotic indices, the Ephemeroptera, Plecoptera, and Trichoptera (i.e., EPT taxa). A spanning logjam composed of three logs bound together was installed perpendicular to stream flow at the impact site. Initial sampling of the impact site and an upstream control found no differences among the ETP taxa. A year after installation, the logjam accumulated woody debris and altered flow so that near-bed current at the impact site was faster and more heterogeneous than at the control site. Although the richness and abundance of the macroinvertebrate community as a whole did not differ between sites after one year, it did for the Ephemeroptera and Plecoptera at the impact site. By contrast, Trichoptera richness and abundance did not change. Our results lend support to the hypothesis that installed logjams may enhance stream habitat not only by providing colonization surfaces for macroinverbrates, but also by altering the benthic environment of the surrounding habitat.

Application of the new multimetric MMI_PL index for biological water quality assessment in reference and human-impacted streams (Poland, the Slovak Republic)

Publication date: Available online 16 September 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Iga Lewin , Szymon Jusik , Krzysztof Szoszkiewicz , Izabela Czerniawska-Kusza , Agnieszka Ewa Ławniczak
A new multimetric MMI_PL index, which is based on the macroinvertebrate composition and combines six single key metrics, has already been implemented in Poland according to the requirements of the EU Water Framework Directive. The objectives of our survey were to assess the biological water quality using the new multimetric MMI_PL index in both reference and human-impacted streams, to analyse whether the values of the new multimetric index properly reflect the ecological status of the water in upland and mountain streams as well as to determine which environmental factors influence the distribution of benthic macroinvertebrates and the values of the metrics. The study was carried out from 2007 to 2010 in three Ecoregions that were established by the EU WFD. A total of 60 sampling sites: 36 reference sites that were situated in the headwaters of mountain streams at mid- and high altitudes and 24, human-impacted sampling sites were selected. The benthic macroinvertebrate surveys were supported by both a hydromorphological and macrophyte assessment according to the River Habitat Survey (RHS) and to the Macrophyte Methods for Rivers. Canonical correspondence analysis (CCA) showed that the values of the Habitat Quality Assessment (HQA) index, conductivity, pH and altitude were the parameters most associated (statistically significant) with the distribution of benthic macroinvertebrate taxa and the values of the metrics in both the reference and human-impacted (impaired) sections of the streams in Ecoregions 9, 10 and 14. The new MMI_PL index was useful for biological water quality assessment and was also important for separating both the reference and impaired sections of streams. The MMI_PL index and some key metrics performed contrary to what was expected in relation to the reference high-altitude siliceous streams (the High Tatra Mts., Ecoregion 10). Low values of multimetric index and key metrics did not properly reflect their high ecological status and pristine character as reflected by the hydromorphological (RHS) and macrophyte surveys or the physical and chemical parameters of the water.

Effects of internal phosphorus loading on nutrient limitation in a eutrophic reservoir

Publication date: Available online 6 September 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Stephen J. Nikolai , Andrew R. Dzialowski
While lake and reservoir management has historically focused on controlling external nutrient loads to improve water quality, internal mechanisms can also contribute to the processes of eutrophication. We assessed how the release of phosphorus (P) from anoxic sediments in the hypolimnion of a eutrophic reservoir affected epilimnetic nutrient concentrations and ratios. We also conducted nutrient bioassay experiments to determine if water column total nitrogen:total P (TN:TP) ratios could be used to predict nutrient limitation in the reservoir. We estimated that anoxic sediments from the lacustrine zone of the reservoir released 7.1 mg P/m2/day into the reservoir during stratification. This internal load was an important source of P to the epilimnion of the reservoir that helped to lower TN:TP ratios and create N limiting conditions following thermocline erosion. With respect to the enrichment bioassays, we found that nutrient limitation varied both spatially and temporally in the reservoir with observed periods of no nutrient limitation, N limitation, P limitation, and N and P co-limitation. However, corresponding water column TN:TP ratios correctly identified the limiting nutrient in less than 50% of the nutrient bioassays. As such, total nutrient ratios should be used with caution when trying to predict nutrient limitation in individual systems.

Internal waves and mixing in a stratified reservoir: insights from three-dimensional modeling

Publication date: Available online 2 September 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Serghei A. Bocaniov , Christian Ullmann , Karsten Rinke , Kevin G. Lamb , Bertram Boehrer
In this study, the 3-dimensional (3D) Estuary and Lake Computer Model (ELCOM) was used to model a mid-sized reservoir (Rappbode Reservoir, Germany) during the period of summer stratification to identify and illustrate the source of internal waves as well as to characterize the water exchange between the hypolimnion and epilimnion under different wind speed conditions with a focal point on one episode of high and sustained winds. The modeling revealed that wind stress was the key driver of the observed internal waves while the role of water withdrawal was negligible. Our results also showed that within the range of wind speeds considered, wind-induced upwelling greatly enhanced mixing between the hypolimnion and epilimnion with a rate that varies approximately as the square of the wind speed. This numerical correlation affirmed that processes connected to wind stress, i.e. internal waves or direct upwelling, were responsible for the mixing of the hypolimnetic water into the surface water rather than direct input of turbulent kinetic energy.

Conservation status of the freshwater pearl mussel Margaritifera margaritifera in Portugal

Publication date: Available online 27 August 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Ronaldo Sousa , Ângela Amorim , Elsa Froufe , Simone Varandas , Amílcar Teixeira , Manuel Lopes-Lima
Based on new information, the current conservation status of the freshwater pearl mussel Margaritifera margaritifera (Linnaeus, 1758) in Portugal is revised. Between 2010 and 2013 surveys were conducted in eight different rivers to assess distribution, abundance, size-frequency and preferential habitat of this species. Rivers Neiva, Cávado and Terva presented very low abundances (in the Cávado no specimens were found) and showed acute signs of ageing, calling into question the future survival of these populations. Although abundances were low in Rivers Beça, Paiva and Mente, juveniles were present and populations may improve their conservation status in the future, if appropriate management measures are applied. Rivers Rabaçal and Tuela presented the highest abundances of adults and juveniles and these two rivers have the highest potential for the conservation of freshwater pearl mussels in Portugal. However, these two populations have suffered severe declines in several stretches due to the construction of dams in recent years. Given that the Portuguese pearl mussel populations are at the southern range of the species distribution, their conservation should be a priority. This current description of the conservation status of M. margaritifera in Portugal can be used as a reference, and guide future research and management initiatives to better conserve this species.

River bed stability versus clogged interstitial: Depth-dependent accumulation of substances in freshwater pearl mussel (Margaritifera margaritifera L.) habitats in Austrian streams as a function of hydromorphological parameters

Publication date: Available online 27 August 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Christian Scheder , Birgit Lerchegger , Peter Flödl , Daniela Csar , Clemens Gumpinger , Christoph Hauer
Substrate conditions are considered crucial for the survival of juvenile freshwater pearl mussels ( Margaritifera margaritifera L.)–and therefore for the recovery of overaged populations in danger of extinction–as fine sediments can clog the interstitial habitat and hamper water and oxygen circulation to the juveniles. Watercourses and their bed sediments must meet two seemingly diametrically opposite requirements in order to offer the freshwater pearl mussel appropriate habitats: stable substrates for all live stages and an unclogged interstitial for the juveniles. As only few scientific publications deal with subsurface conditions in pearl mussel brooks, the present preliminary study tries to contribute to this topic by compiling a variety of chemical and hydromorphological data from several Austrian watercourses with distinctly different characteristics. It was clearly shown that discharge patterns, hydraulic pressure, water depths and flow velocities affect both river bed stability and the perfusion of the hyporheic zone: In an artificial millrace with permanent low flow conditions and a permanently stable substrate a distinct barrier was detected within the first 5 cm substrate depth that totally blocks the interchange between surface and interstitial water, resulting in an accumulation of substances of all kinds, among them potentially toxic substances. Such a barrier was also found to be building up in several natural watercourses, clearly indicating the danger of adverse land-use and of long-term low flow conditions in smaller brooks (given that the local decrease in precipitation, proven in long-term studies, proceeds). Significant differences in substrate concentrations in the interstitial water were detected between watercourses, whereas chemical conditions in the surface water exhibited no differences at all. An accompanying biomonitoring study showed high survival rates all over the study area, indicating the suitability of juvenile freshwater pearl mussels as bioindicators in terms of surface water, but not of interstitial water.

Influence of stock origin and environmental conditions on the survival and growth of juvenile freshwater pearl mussels (Margaritifera margaritifera) in a cross-exposure experiment

Publication date: Available online 27 August 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Marco Denic , Jens-Eike Tauebert , Michael Lange , Frankie Thielen , Christian Scheder , Clemens Gumpinger , Juergen Geist
The freshwater pearl mussel ( Margaritifera margaritifera ) is a highly specialized and sensitive freshwater bivalve, whose survival in the juvenile phase is indicative of high quality habitats. This contribution investigates the use of juvenile freshwater pearl mussels as bioindicators, considering the influence of mussel stock and study stream conditions on juvenile performance, as described by survival and growth rates. A standardized cross experiment was carried out investigating juvenile performance in four different pearl mussel stocks originating from the Rhine, Danube and Elbe drainages, representing distinct genetic conservation units. The juveniles were exposed in five study streams which were selected to integrate pearl mussel streams with different water qualities and recruitment status of the mussel population. Per study stream, five standard mesh cages containing an equal number of 20 (10 × 2) juvenile pearl mussels per stock in separate chambers were installed. Survival and growth rates of juveniles were checked after three months (i.e. before their first winter) and after nine months (i.e. after their first winter). Mussel stock and study stream conditions significantly influenced juvenile performance. Growth rates were determined by study stream conditions and increased with stream water temperature, organic carbon and C/N ratios. Survival rates varied stock-specifically, indicating different levels of local adaptation to their native streams. Due to the detection of stream-specific differences in juvenile performance, freshwater pearl mussels appear suitable as bioindicators. However, a careful of consideration of stock-specificity is necessary to avoid false interpretation of bioindication results. The comparison of stock-specific survival in native versus non-native streams implicates that exposure of juveniles outside their native habitats is able to increase breeding success or else serve for risk spreading in breeding programs.

Does grazing change algal communities from grassland and pine afforested streams?: A laboratory approach

Publication date: Available online 27 August 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Luciana Cibils Martina , Javier Márquez , Romina Principe , Noemí Gari , Ricardo Albariño
Drastic changes in the composition and physiognomy of riparian vegetation, such as the conversion of grassland to forest, are expected to alter interactions among light availability, primary producers and herbivores. Our aim was to examine in laboratory the influence of a ubiquitous grazer on periphyton grown in a grassland unshaded stream (reference) vs. periphyton from a nearby pine afforested stream. Besides, we evaluated how the community responds to the removal of grazing. Given that grassland streams are exposed to higher light intensity and grazers are more abundant compared to afforested streams, we proposed that if biofilm grown in the afforested stream are dominated by grazing-vulnerable algal species, grazing pressure by Helicopsyche sp. should be stronger. In addition, if biofilm from the afforested stream has low quality or is less abundant as food for consumers, the effects of Helicopsyche sp. may be stronger or weaker depending on their feeding decisions. Helicopsyche sp. caused a decrease in richness and diversity in periphyton grown in the grassland stream and its net grazing effect on chlorophyll a (Chl a ) was higher. Algal community composition from grassland stream was strongly changed after grazing, with a decrease in the proportion of overstory algae. In contrast, algal community structure of periphyton from the afforested stream was neither affected by grazing nor by grazing exclusion. Helicopsyche sp. produced significant changes in a short time in structural attributes of algal communities, mainly in periphyton from the grassland stream suggesting that herbivory, as a functional factor, is diminished following afforestation.

A typology for fish-based assessment of the ecological status of lowland lakes with description of the reference fish communities

Publication date: Available online 21 August 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): David Ritterbusch , Uwe Brämick , Thomas Mehner
We compared the potential of different lake typologies to discriminate fish communities in least disturbed sites. The typologies tested were based on morphometric and geographical descriptors. The best discrimination was achieved by distinguishing three lake types according to depth and mixis regime: polymictic lakes, stratified lakes with less than 30 m of maximum depth and deep, stratified lakes with maximum depths above 30 m. We conclude that the proposed typology is appropriate for a system to assess the ecological status of German lakes with the fish fauna according to the Water Framework Directive and might well be transferable to other European assessment systems. The fish communities in all lake types were similar and dominated by few fish species. Perch and roach were the most abundant ones, followed by ruffe, bream, rudd and pike. The fish communities in least disturbed sites might be used as reference conditions in future fish-based assessment systems.

Hydrological connectivity as most probable key driver of chlorophyll and nutrients in oxbow lakes of the Bug River (Poland)

Publication date: March 2014
Source:Limnologica – Ecology and Management of Inland Waters, Volume 46
Author(s): Lech Kufel , Szymon Leśniczuk
Concentrations of chlorophyll, dissolved inorganic nitrogen and phosphorus, total phosphorus and suspended solids were analysed in 10 oxbow lakes of the Bug River in spring and summer. According to their connectivity with the river, all lakes were divided into 3 categories – lakes connected with the river channel but separated from the floodplain inputs, lakes connected with the river but receiving inputs from the floodplain and totally isolated lakes. Connected lakes showed significantly higher concentrations of available nutrients and chlorophyll but the relationship between the two variables was weak in the spring and non-existent in the summer. Suspended solids were also more abundant in connected than in isolated lakes. Analyses of the proportion of chlorophyll and particulate phosphorus in suspension led us to the conclusion that water movement in connected lakes inhibited sedimentation and kept algae in the water column. Isolated oxbow lakes devoid of wind-driven mixing were more susceptible to algal sedimentation which would explain the differences observed between the two lake categories.

Empty native and invasive bivalve shells as benthic habitat modifiers in a large river

Publication date: Available online 21 July 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): E. Bódis , B. Tóth , J. Szekeres , P. Borza , R. Sousa
Bivalves are remarkable ecosystem engineers and their long-lasting shells may provide important physical structures for benthic organisms. In the last decades the Danube River has experienced great changes in the bivalve fauna, i.e. several native species have been declining and several invasive species have been introduced. The invasive Corbicula fluminea and Sinanodonta woodiana are now widespread and produce large amounts of shells. In this study, we investigated empty shells of native ( Anodonta anatina , Unio tumidus ) and invasive ( C. fluminea , S. woodiana ) bivalves (including their mixtures) as benthic substrates and compared them to clay granules (control), which mimics the natural hard substrates in the Danube River (Hungary). Macroinvertebrate colonization was compared between i) empty shells and control substrate; ii) different bivalve species (native and invasive) and iii) three scenarios (before invasion, and short and long time after invasion) by using a mix of empty shells (native, native plus invasive, and invasive species). In comparison to control treatments the empty shells facilitated the presence of amphipods, caddis larvae and isopods, which contributed to a shift in the trophic structure by decreasing the proportion of gathering collectors while increasing the presence of shredders and predators. Several shell traits such as size, outer-shell surface roughness, hardness, thickness, 3D shape and chemical composition may be important attributes in the habitat modifying effects; however, this study could not disentangle which contribute most for the differences found. Given the capability of invasive C. fluminea and S. woodiana to accumulate large amounts of empty shells on several sites of the Danube, its habitat modifying effects can be particularly important, especially on the macroinvertebrate community structure. Moreover, these effects may increase in near future due to the predicted more frequent and severe extreme climatic conditions, which have been responsible for massive mortalities in both species.

A floodplain-scale lake classification based on characteristics of macroinvertebrate assemblages and corresponding environmental properties

Publication date: Available online 20 July 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Baozhu Pan , Hongzhu Wang , Haijun Wang
Floodplain lakes have been experiencing great pressures by human activities, and ecological functions in different types of lakes show different degrees of degradation. For facilitating conservation and management of different types of floodplain lakes, it is necessary to classify the lakes into similar groups according to certain standards. In this study, on basis of consideration of macroinvertebrate assemblages and corresponding environmental properties, the Yangtze floodplain lakes were classified into three major types grouping five groups of lakes: 1) river-disconnected lakes (algal lakes, macrophytic-algal transition lakes, and macrophytic lakes), 2) semi-connected lakes (oxbow lakes), 3) river-connected lakes. The classification of floodplain lakes mainly reflects the gradients of trophic and hydrological connectivity. The key factors structuring macroinvertebrate assemblages in the Yangtze floodplain lakes were mainly hydrological (connectivity rating, water depth), trophic (total phosphorus, macrophytes biomass) and morphometric (development of lake shoreline). Among the floodplain lakes, ecological status of river-connected lakes, where biodiversity, biomass and production of macroinvertebrates reached maxima, has been confirmed to be the best. From the view of conservation and management of the entire floodplain lakes, it is suggested that protecting the remnants of river-connected lakes, controlling eutrophication and linking disconnected lakes freely with the mainstream are crucial.

Environmental factors associated with heterotrophic nitrogen-fixing bacteria in water, sediment, and riparian soil of Suquía River

Publication date: Available online 9 July 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Merlo Carolina , Reyna Luciana , Abril Adriana , Amé María Valeria , Genti-Raimondi Susana
In this study we investigated the environmental factors associated with biological nitrogen (N) fixation (BNF) in water, sediments, and riparian soil along a polluted river (Suquía River of Córdoba, Argentina). Here, we screened heterotrophic nitrogen-fixing bacteria and assessed the magnitude of BNF at different sites of Suquía River. To this aim, samples of the three habitats (riparian soil, water, and sediment) were collected from five polluted sites and one reference site during low and high flow water periods. In all samples the abundance of N-fixing bacteria was evaluated in solid nitrogen-free medium and the biological N fixation was measured by nitrogenase (Nase) enzyme activity using the acetylene reduction method. To identify the heterotrophic N-fixing taxa DNA of nine cultures isolated from sites with different Nase enzyme activity was extracted and the 16S rRNA gene was amplified and sequenced. In addition, the ammonia and organic carbon (C) content in all samples, the dissolved O 2 concentration in water, and the water content in riparian soil were measured. The N-fixing bacteria were detected in all study sites and habitats. The abundance of them correlated significantly with organic C content in sediment, and with water and organic C contents in riparian soil, whereas in water a negative correlation with dissolved O 2 was observed. In addition, the water and sediment Nase enzyme activity varied among sites during low flow period presenting significant correlation with ammonia and organic C contents in sediment. The identified taxonomic groups in the Suquía River are related to Alphaproteobacteria , Betaproteobacteria, Gammaproteobacteria , and Actinobacteria although the N-fixing capacity of them was not established. Altogether these findings demonstrate that BNF occurs in all habitats of Suquía River, being in sediments influenced mainly by the higher organic C present in the most polluted sites, while in riparian soil the organic C and water contents were the major abiotic factors that control the abundance of N fixing bacteria. In Suquía River water the density of N fixing bacteria were associated with low dissolved O 2 concentration. These data suggest that the BNF in Suquía River is a complex process that depends on numerous environmental factors that act together.

Does filter type and pore size influence spectroscopic analysis of freshwater chromophoric DOM composition?

Publication date: Available online 9 July 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Jorge Nimptsch , Stefan Woelfl , Brian Kronvang , Ricardo Giesecke , Humberto E. González , Luciano Caputo , Jörg Gelbrecht , Wolf von Tuempling , Daniel Graeber
Dissolved organic matter (DOM) in freshwater ecosystems has its origin in a multitude of terrestrial and aquatic sources which determine amount, composition and thereby its functions. Spectroscopic methods are used to characterize chromophoric DOM. Among these methods, absorbance and fluorescence spectroscopy can provide indications of sources, behavior, and biogeochemical cycling of DOM. Since DOM is defined as the part of the organic matter pool which passes filters from 0.22 to 0.7 μm, sample filtration is required before spectroscopic measurements can be done. However, the use of different filter types might be influencing the results of DOM composition measurements. In order to assess the effect of different filters, we used three filter types with nominal pore sizes of 0.7, 0.45 or 0.22 μm, measured difference spectra, calculated spectroscopic indexes (S 275-295 , S 350-400 , S r , SUVA 254 , E2:E3, fluorescence index, β: α, humification index) and fluorescence components (parallel factor analysis, PARAFAC), obtained via spectroscopic measurements from water with different characteristics (e.g. river water, wetland, sewage effluent). Our results show that the filter types had significant but small effects on the chromophoric DOM composition and that meta-analyses of DOM composition based on studies with different pore size can be done, when keeping potential minor filtration effects in mind. This is important for further meta-analysis which might inter-compare data sets on spectroscopic characterization of DOM

Can recently-hatched crayfish cling to moving ducks and be transported during flight?

Publication date: Available online 9 July 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): M. Águas , F. Banha , M. Marques , P.M. Anastácio
The red swamp crayfish ( Procambarus clarkii ) is a freshwater invasive species which has become a worldwide problem. Recent work on ectozoochory of freshwater macrocrustacean species indicated that there might be a possibility of transport of recently-hatched crayfish by birds. In this context, we applied a new set of methods to quantify the probability of transport of recently-hatched crayfish, namely with moving animal vectors. First, we tested the desiccation resistance of crayfish and the capacity of crayfish to cling to mallard’s feet, depending on the standing time of the feet. We also determined the ability of recently-hatched crayfish to cling to an artificially moving freshly dead mallard ( Anas platyrhynchos ) and finally, we determined the time required for the death of 50% and 90% of the individuals of recently-hatched crayfish under conditions similar to those of mallard flight. Recently-hatched crayfish were able to survive up to 225 minutes out of water, withstanding longer at a lower temperature and therefore transport does not seem to be limited by desiccation survival. The duration of the standing period of duck’s feet positively affected the probability of transport of crayfish. Recently-hatched crayfish were able to cling to a moving duck and the probability of clinging was significantly affected by the water depth, being lower at greater depths. Moreover, when transported on a freshly dead duck under flight simulation conditions the time required for the death of 50% and 90% of the individuals were 2 min 14 sec and 4 min 53 sec respectively. These flight durations correspond to transport distances of 2.8 km and 6.1 km respectively, which is enough for transport to another aquatic system. The results demonstrate that passive transport of recently hatched P. clarkii by actively moving waterbirds is possible, and therefore it will likely enhance the local process of invasion.

Intra- and interspecific variations in life strategies of Erpobdella octoculata and Erpobdella vilnensis in different habitats along the longitudinal gradient of stream

Publication date: July 2014
Source:Limnologica – Ecology and Management of Inland Waters, Volume 48
Author(s): Pavel Beracko , Alexandra Rogánska
Our study examines intra and interspecific variations in life histories, reproduction parameters, secondary production and feeding biology of two erpobdellid leech species ( Erpobdella octoculata and Erpobdella vilnensis ) across longitudinal gradient of streams. These species frequently cohabit in streams of Central Europe and present a very high niche overlap in terms of spatial distribution and trophic resources. In both species, a shift from biennial to annual life cycle was noted, as well as from iteroparity to semelparity. In general, annual erpobdellid populations invested more in reproduction than the biennial populations and E. octoculata invested more in reproduction than any E. vilnensis . The absolute individual growths of studied species were described by the von Bertalanffy growth model with seasonal oscillations. The highest values of daily growths (6.1–8.6% of dry mass per day) were noted during the first month after hatching. Annual production ranged for E. vilnensis from 3.48 to 10.01 g formalin mass m−2 year−1 and for E. octoculata from 11.29 to 19.29 g formalin mass m−2 year−1. The prey diversity and overlap of prey composition and potential prey resources of leeches indicate that, compared to older leeches, the younger leeches are more selective feeders.

Structural and functional response to metal toxicity in aquatic Cyperus alopecuroides Rottb

Publication date: Available online 18 June 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Riffat Batool , Mansoor Hameed , Muhammad Ashraf , Sana Fatima , Tahira Nawaz , Muhammad Sajid Aqeel Ahmad
Morpho-anatomical and physiological response of Cyperus alopecuroides Rottb. (Family Cyperaceae), occurring in industrial-polluted water near Sheikhupura, Pakistan to metal (Ni and Cd) stress was examined. Two levels (30 and 60 mg L−1) of each of Ni and Cd were maintained during the experiment. Growth and development was severely affected by both metals, however, Cd was more toxic than Ni, although Ni was absorbed readily by the roots and its considerable amount was translocated to aerial plant parts due to its mobile nature. In contrast, high amount of Cd were retained in the roots. Specific root physio-anatomical modifications for Ni tolerance were found result from leaf turgor potential, high accumulation of organic osmolytes, enhanced sclerification, and aerenchyma formation, while leaves were more developed bulliform cells and stellate parenchyma. Cd tolerance was found to be related to accumulation of organic osmolytes, thick epidermis and endodermis, enhanced sclerification, and stellate cell formation in stem, and well developed bulliform cells in leaves. The structural and functional response of metal toxicity was very specific in C. alopecuroides depending on the type of metal which enabled this species to survive successfully in metal-polluted wetlands.

Long-term macrophyte mapping documents a continuously shift from native to non-native aquatic plant dominance in the thermally abnormal River Erft (North Rhine-Westphalia, Germany)

Publication date: Available online 2 June 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Andreas Hussner
Macrophyte mappings of a 37 km stretch of the thermally abnormal Erft River in 2003, 2005, 2007, 2011 and 2013 documented the presence of nine alien ( Azolla filiculoides , Egeria densa , Eichhornia crassipes , Hydrocotyle ranunculoides , Hygrophila polysperma , Lemna minuta , Myriophyllum aquaticum , Pistia stratiotes and Vallisneria spiralis ) in addition to 15 native species. During the study period, the number of native plant species decreased significantly in the river sections, while the number of alien species remained constant. The relative plant mass (RPM) of native species decreased from 67 to 33%, while that of the alien species increased. Only two of the nine reported alien species ( V. spiralis and P. stratiotes ) increased their abundances within the study period and became the most dominant species in the Erft River, while the other introduced species did not show mass development. The highest decline in RPM have been found for native Sparganium emersum and alien E. densa. Summarizing, the evergreen alien V. spiralis and recently P. stratiotes were the most successful invader within this thermally abnormal river since 2003, most likely profiting from the high winter temperatures >10 °C and displacing native vegetation, particularly formerly widespread native S. emersum .

The influence of biotope on invertebrate assemblages in lentic environments: a study of two perennial alkaline wetlands in the Western Cape, South Africa

Publication date: Available online 2 June 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Matthew S. Bird , Jenny A. Day , Heather L. Malan
As a step towards the biological assessment of wetlands in South Africa, this study investigates the influence of biotope characteristics on the spatial distribution of aquatic invertebrates. The aim was to assess whether different wetland biotopes support significantly different invertebrate assemblages in terms of the composition and abundance of microcrustaceans and macroinvertebrate taxa. During October 2006, three different biotopes were sampled within Verlorenvlei and Wave’s Edge wetlands (Western Cape, South Africa) using a long-handled sweep net. Composition and abundance of invertebrate assemblages were compared between and within sites for each of the wetlands. Assemblage composition generally differed among biotopes within each wetland, as revealed by cluster analysis and MDS plots. At Verlorenvlei, biotopes formed distinctive clusters with low site-specific variability. Assemblage composition at Wave’s Edge revealed coarser groupings with clusters distinguishing between vegetated and non-vegetated biotopes only. Biotopes within each wetland differed significantly in terms of taxon richness, Shannon diversity and mean total invertebrate biomass (g.m−3), whilst mean total density (ind.m−3) differed only between biotopes in Verlorenvlei. Considerable shifts in invertebrate assemblage structure corresponded to differences in conductivity among sites at Verlorenvlei. For large physico-chemically heterogeneous wetlands such as Verlorenvlei, it is suggested that smaller physico-chemically homogenous zones should be identified a priori and within these areas vegetated biotopes should be sampled over the broadest possible spatial scale, whilst open-water biotopes can be sampled more narrowly. For small, reasonably homogenous wetlands such as Wave’s Edge, we suggest a less broad spatial representation of biotopes and instead one should concentrate on increasing the number of sample repetitions per site.

Intra- and Interspecific variations in life strategies of Erpobdella octoculata and E. vilnensis in different habitats along the longitudinal gradient of stream

Publication date: Available online 29 May 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Pavel Beracko , Alexandra Rogánska
Our study examines intra and interscpecific variations in life histories, reproduction parameters, secondary production and feeding biology of two erpobdellid leech species ( Erpobdella octoculata and Erpobdella vilnensis ) across longitudinal gradient of streams. These species frequently cohabit in streams of Central Europe and present a very high niche overlap in terms of spatial distribution and trophic resources. In both species, a shift from biennial to annual life cycle was noted, as well as from iteroparity to semelparity. In general, annual erpobdellid populations invested more in reproduction than the biennial populations and E. octoculata invested more in reproduction than any E. vilnensis . The absolute individual growths of studied species were described by the von Bertalanffy growth model with seasonal oscillations. The highest values of daily growths (6.1–8.6% of dry mass per day) were noted during the first month after hatching. Annual production ranged for E. vilnensis from 3.48 to 10.01 g formalin mass m-2 year-1 and for E. octoculata from 11.29 to 19.29 g formalin mass m-2 year-1. The prey diversity and overlap of prey composition and potential prey resources of leeches indicate that, compared to older leeches, the younger leeches are more selective feeders.

Drivers of phytoplankton, bacterioplankton, and zooplankton carbon biomass in tropical hydroelectric reservoirs

Publication date: Available online 20 May 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Lúcia H.S. da Silva , Vera L.M. Huszar , Marcelo M. Marinho , Luciana M. Rangel , Jandeson Brasil , Carolina D. Domingues , Christina C. Branco , Fábio Roland
Studies of carbon sources in plankton communities are important because carbon content has become the main currency used in functional studies of aquatic ecosystems. We evaluated the contribution to the total organic carbon pool from different plankton communities (phytoplankton, bacterioplankton, and zooplankton–C-biota) and its drivers in eight tropical hydroelectric reservoirs with different trophic and hydrological status and different physical features. Our systems were separated into three groups based on trophic status and water residence time: i) mesotrophic with low residence time (ML); ii) mesotrophic with high residence time (MH); and iii) eutrophic with low residence time (EL). Our hypothesis that reservoirs with low water residence times and low nutrient concentrations would show the lowest C-biota was supported. Phytoplankton carbon (C-phy) showed the highest concentrations in the EL, followed by MH and ML systems. The EL group also showed significantly higher zooplankton carbon (C-zoo). No significant difference was observed for bacteria carbon (C-bac) among the three system groups. In addition to trophic status and water residence time, regression analyses revealed that water temperature, light, pH, and dissolved organic carbon concentrations were the main drivers of plankton communities in these large tropical hydroelectric reservoirs.

Humic Substances: the answer to improved mayfly survivorship in acidic environments?

Publication date: Available online 15 May 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Aleicia Holland , Leo J. Duivenvoorden , Susan H.W. Kinnear
Acidification of freshwaters via anthropogenic means is a global problem. Decreases in pH in these systems have devastating effects on macroinvertebrate fauna especially Ephemeropterans. However, fauna in naturally acidic waters with high concentrations of humic substances (HS) appear to be less affected by acidification. This study investigated the ability of HS to decrease toxicity of low pH to mayflies ( Atalophlebia spp.) in both hard and soft water environments. Laboratory trialling with both hard and soft water was conducted to represent water chemistries commonly associated with anthropogenic and naturally acidic freshwaters. Mayflies were exposed to decreases in pH between 7 (control) and 3.5 in the presence of 0, 10 and 20 mg/L HS (Aldrich humic acid). HS increased mayfly survival by up to 45% in soft water and up to 39% in hard water. HS were also shown to increase 96 hour LC 50 values in both soft (4.29, 0 mg/L; 3.99, 10 mg/L and 3.97, 20 mg/L) and hard water (4.58, 0 mg/L; 4.22, 10 mg/L and 4.07, 20 mg/L). The results of this study are important in showing that HS can influence the toxicity of low pH environments; thus providing insight into why contrasting effects on biota are recorded from naturally acidic compared with anthropogenically-acidified environments

Reproductive traits and conservation needs of the endemic gammarid Laurogammarus scutarensis (Schäferna, 1922) from the Skadar Lake system, Balkan Peninsula

Publication date: Available online 4 May 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Michał Grabowski , Karolina Bącela-Spychalska , Vladimir Pešić
Europe is one of the global hotspots of freshwater amphipod diversity with a number of endemic species yet many of European freshwater ecosystems are under extreme anthropogenic pressure. Studying the biology and ecology of endemic species may substantially help to assess risk of extinction and define proxies for their conservation. Laurogammarus scutarensis is a Balkan endemic and the only species within the genus Laurogammarus G. Karaman 1984. Its distribution is restricted to temperature-stable, cool waters of the springs, streams and lower sections of a few rivers emptying to the north-western part of the Skadar Lake in Montenegro–an area under heavy anthropogenic pressure in recent years. We examined life history of the species in a limnocrene spring with year-round stable temperature (10 °C ± 0.5) by estimating its population structure over a year, fecundity, reproductive period and relationship between photoperiod and reproduction. These parameters were compared to those of other gammarids, including invasive species, in order to estimate the role of photoperiod in shaping life history of L. scutarensis , and to give insight into the possible conservation needs for that species. Our results show that the species is univoltine and its reproduction continues round the year. However, its intensity is synchronised with seasonal day length changes with the highest share of females breeding in spring and early summer. The population sex structure is strongly female biased in most of the year. Number of eggs laid depends positively on the female body length; however the mean brood size (15.53 eggs) of L. scutarensis is rather low when compared to other species. Also partial fecundity and mean body length at which individuals start to reproduce indicate that its reproductive potential is much lower than that of many other gammarid species, including those colonizing many European water bodies in recent years. Concluding, the studied life history traits of L. scutarensis combined with its very narrow distribution range and peculiar thermal requirements reported in the literature provide as with the hint to define the species as vulnerable to threats posed by the habitat degradation and competition with other species. Taking into account the risk of invasion by alien species and progressive habitat loss, we are of the opinion that L. scutarensis should be recognised as an endangered species and that a conservation plan should be implement to prevent its possible extinction.

Implementing the Water Framework Directive in overseas Europe: a multimetric macroinvertebrate index for river bioassessment in Caribbean islands

Publication date: Available online 4 May 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Heliott Touron-Poncet , Caroline Bernadet , Arthur Compin , Nicolas Bargier , Régis Céréghino
Neotropical overseas regions of Europe have the same water policy objectives as the continental ones, but were overlooked during recent developments of bioassessment tools that fulfill the Water Framework Directive guidelines. We designed a macroinvertebrate-based multimetric index (IBMA) to assess ecological health in rivers of Martinique and Guadeloupe, two densely populated islands in the Lesser Antilles (Caribbean Sea). Invertebrates were sampled at 114 sites including reference and impacted river reaches following a normalized protocol. Among the 411 biological metrics calculated from our site-specific data, we selected metrics exhibiting the best trade-off between high discrimination efficiency, low specificity, low redundancy, and high stability under reference conditions. We finally retained seven metrics related to taxonomic diversity, species abundance, and preferences for some substratum types. Each metric was weighted by its discrimination efficiency. Using test data sets, we found that the IBMA was sensitive to the full range of disturbances in the area. Also, our index improved the detection of impairments, compared to the former practice by regional administrations. Finally, we suggest that the IBMA might prove relevant to neighboring islands in the biogeographic area.

The importance of species replacement and richness differences in small-scale diversity patterns of aquatic macroinvertebrates in spring fens

Publication date: Available online 6 April 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Vanda Rádková , Vít Syrovátka , Jindřiška Bojková , Jana Schenková , Vendula Křoupalová , Michal Horsák
This study provides new information on beta diversity (variation in species composition across space) of three invertebrate groups (Clitellata, Plecoptera, and Chironomidae) on a small, within-site spatial scale. It was conducted at small-sized spring fens where two contrasting mesohabitats, a flowing-water and a standing-water, can be clearly distinguished. Besides flow conditions, these habitats differed in the amounts of inorganic substratum and dissolved oxygen. Factors related to flow conditions (dissolved oxygen and water temperature) influenced the composition of the studied assemblages at both mesohabitats, while substratum features were important at the standing-water habitat. The water chemistry was important for Clitellata at both mesohabitats and for Chironomidae at the flowing-water. Using a new approach of disentangling beta diversity into two components (species replacement and species richness differences), clear difference in beta diversity patterns among the three assemblages were found, despite their roughly equal total beta diversities. Variation in species composition of those assemblages strongly limited by flow conditions (Plecoptera and partly Clitellata) was induced by differences in species richness, while replacement governed the variation in species rich assemblages that were able to utilise a wide range of conditions (Chironomidae and partly Clitellata). These results indicate that the size of species pool and the level of environmental filtering play an important role in forming beta diversity patterns, and caution that the same amount of beta diversity can be promoted by essentially different mechanisms, even at a very fine spatial scale with no involvement of dispersal limitations.

Modelling Lake Kivu water level variations over the last seven decades

Publication date: Available online 13 March 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Fabrice A. Muvundja , Alfred Wüest , Mwapu Isumbisho , Mwenyimali B. Kaningini , Natacha Pasche , Päivi Rinta , Martin Schmid
This study aimed at analysing the hydrological changes in the Lake Kivu Basin over the last seven decades with focus on the response of the lake water level to meteorological factors and hydropower dam construction. Historical precipitation and lake water levels were acquired from literature, local agencies and from global databases in order to compile a coherent dataset. The net lake inflow was modelled using a soil water balance model and the water levels were reconstructed using a parsimonious lake water balance model. The soil water balance shows that 370 mm yr−1 (25%) of the precipitation in the catchment contributes to the runoff and baseflow whereas 1100 mm yr−1 (75%) contributes to the evapotranspiration. A review of the lake water balance resulted in the following estimates of hydrological contributions: 55%, 25%, and 20% of the overall inputs from precipitation, surface inflows, and subaquatic groundwater discharge, respectively. The overall losses were 58% and 42% for lake surface evaporation and outflow discharge, respectively. The hydrological model used indicated a remarkable sensitivity of the lake water levels to hydrometeorological variability up to 1977, when the outflow bed was artificially widened.

Replacement of culvert styles has minimal impact on benthic macroinvertebrates in forested, mountainous streams of Northern California

Publication date: Available online 13 March 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Justin E. Lawrence , Matthew R. Cover , Christine L. May , Vincent H. Resh
Culvert styles are being replaced on many road-stream crossings to provide long-term (>2 years) benefits, but these projects may result in short-term (0-2 years) biological impacts. We quantified the short-term effects of replacing steel-pipe culverts with open-arch structures on the benthic-macroinvertebrate communities of 6 streams in the Klamath National Forest of Northern California USA. Physical habitat showed notable site-specific effects in channel form and sedimentation, but no significant change among sites. In contrast, we observed small though significant impacts of the culvert style replacement on benthic macroinvertebrates among sites, including a statistically significant reduction in both taxa richness (p = 0.012) and abundance of intolerant taxa (p = 0.004). Moreover, there was also modest evidence of slightly elevated variability in the benthic-macroinvertebrate communities downstream following the replacement of culvert style. The long-term benefits of culvert style replacement that have been observed in other studies may outweigh the minor, short-term biological impacts observed in these streams.

Anthropogenic land-use signals propagate through stream food webs in a California, USA, watershed

Publication date: March 2014
Source:Limnologica – Ecology and Management of Inland Waters, Volume 46
Author(s): Jonathan W. Moore , Timothy D. Lambert , Walter N. Heady , Susanna E. Honig , Ann-Marie K. Osterback , Corey C. Phillis , Angela L. Quiros , Nicolas A. Retford , David B. Herbst
Human development of watersheds can change aquatic ecosystems via multiple pathways. For instance, human rural development may add nutrients to ecosystems. We used naturally occurring stable isotopes in stream food webs to investigate how land use affects stream ecosystems across a gradient of land development in the San Lorenzo watershed, California. Road density was used as a proxy for land development. We found that streams in watersheds with higher road densities had elevated concentrations of phosphate and nitrate. Furthermore, algal δ15N values increased as a function of nitrate concentration, but saturated at approximately 6‰. This saturating pattern was consistent with a two-source mixing model with anthropogenic and watershed sources, fit using Bayesian model fitting. In sites that had >2.6 km roads km−2, anthropogenic sources of N were estimated to represent >90% of the N pool. This anthropogenic N signal was propagated to stream consumers: rainbow trout ( Oncorhynchus mykiss ), signal crayfish ( Pacifasticus leniusculus ), and benthic invertebrate δ15N were positively correlated with algal δ15N. Even relatively low density rural human land use may have substantial impacts on nutrient cycling of stream ecosystems.

Dietary supply with essential lipids affects growth and survival of the amphipod Gammarus roeselii

Publication date: March 2014
Source:Limnologica – Ecology and Management of Inland Waters, Volume 46
Author(s): René Gergs , Nicole Steinberger , Timo Basen , Dominik Martin-Creuzburg
Growth and survival of benthic macroinvertebrates depend on the availability and the quality of potential food sources. The significance of essential biochemical nutrients, such as sterols and polyunsaturated fatty acids (PUFAs), for benthic invertebrates has been insufficiently studied. We investigated the effects of these essential lipids on growth and survival of the benthic gammarid Gammarus roeselii , a widespread species in streams, rivers and lentic waters of Central Europe, in standardized feeding experiments. Juvenile gammarids were fed a mixture of three cyanobacteria with no evidence of toxin production, either unsupplemented or supplemented with cholesterol or the long-chain PUFA docosahexaenoic acid (DHA) using bovine serum albumin (BSA) to load algal or cyanobacterial cells with single lipid, and a mixture of three eukaryotic algae containing various sterols and long-chain PUFAs. Our results revealed that growth and especially survival of gammarids on the cyanobacterial diet significantly increased upon supplementation with cholesterol and DHA, indicating that the nutritional inadequacy of cyanobacteria for gammarids and potentially other benthic invertebrates is at least partially due to a deficiency in these essential lipids. We propose that the expected increase in the frequency of pelagic cyanobacterial mass developments as a consequence of global warming will also affect benthic food web processes to an as-yet-unknown magnitude.

Fecundity of the mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae): A long-term study in the River Rhine

Publication date: Available online 23 February 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Armin Kureck , Rosita Bieg , Rosalinde Wendeler , Jost Borcherding
The fecundity of the mayfly Ephoron virgo in the River Rhine was studied over a period of twelve years (1992-2003) and compared in four European rivers in 1998. The field data were complemented by mass-rearing in flumes with fresh running river water (1999-2001). The dry mass of a single egg averaged to 4.15 ± 0.25 μg, without any significant spatial or temporal differences. Total egg mass per female was found as a reliable measurement of fecundity in E. virgo that significantly increased with increasing weight of a female. Within a sample, individual females differed tremendously in egg numbers. This high variability even remained under more homogenous conditions in a densely populated experimental flume. In 1998, fecundity of E. virgo in the Rhine tributaries Main and Neckar was significantly lower than in the rivers Rhine and Lahn, averaging between about 2500 and 4100 eggs per female, respectively. Fecundity did not differ throughout the flight period at the Rhine. Though differences in fecundity between 1992 and 2003 were observed in the Rhine, no clear temporal tendency could be detected. Under extremely high population densities of E. virgo in experimental flumes, fecundity was slightly lower compared to parallel field samples. Based on these fecundity data, the decline of the population of E. virgo in the Lower Rhine is discussed with respect to some potential environmental factors, giving clear hints that it is not a simple effect of food limitation.

Anthropogenic land-use signals propagate through stream food webs in a California, U.S.A, watershed

Publication date: Available online 9 February 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Jonathan W. Moore , Timothy D. Lambert , Walter N. Heady , Susanna E. Honig , Ann-Marie K. Osterback , Corey C. Phillis , Angela L. Quiros , Nicolas A. Retford , David B. Herbst
Human development of watersheds can change aquatic ecosystems via multiple pathways. For instance, human rural development may add nutrients to ecosystems. We used naturally occurring stable isotopes in stream food webs to investigate how land use affects stream ecosystems across a gradient of land development in the San Lorenzo watershed, California. We used road density as a proxy for land development. We found that streams in watersheds with higher road densities had elevated concentrations of phosphate and nitrate. Furthermore, algal δ15N values increased as a function of nitrate concentration, but saturated at approximately 6‰. This saturating pattern was consistent with a two-source mixing model with anthropogenic and watershed sources, fit using Bayesian model fitting. In sites that had >2.6 km roads km−2, anthropogenic sources of N were estimated to represent >90% of the N pool. This anthropogenic N signal was propagated to stream consumers: rainbow trout ( Oncorhynchus mykiss ), signal crayfish ( Pacifasticus leniusculus ), and benthic invertebrate δ15N were positively correlated with algal δ15N. Even relatively low density rural human land use may have substantial impacts on nutrient cycling of stream ecosystems.

Impact of epilimnetic phosphorus supply and food web structure on phosphorus binding forms in settling material and sediments in a thermally stratified lake

Publication date: Available online 8 February 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Rychła Anna , Gonsiorczyk Thomas , Hupfer Michael , Kasprzak Peter
Knowledge about the contribution of food web structure and nutrient concentration in lakes to phosphorus (P) sedimentation and remobilization at the sediment surface is still poor. Using four large enclosures placed in a eutrophic, thermally stratifying lake, we studied the effects of the structure of the planktonic food web (with and without planktivorous fish, ±F treatments) and nutrient concentration (with and without fertilisation, ±N treatments) on P sedimentation. We investigated the total P content and P binding forms in settling material (TP SM ) and of the uppermost 1 cm sediment layer (TP Sed ) during three consecutive stratification periods (2005–2007). Additionally, epilimnetic P (SRP Epi , TP Epi ), chlorophyll a and biomass of total crustacean and Daphnia were measured. On a seasonal scale, Daphnia biomass tended to negatively influence chlorophyll a, sedimentation rate of total particulate matter and of P, but the latter two criteria did not differ significantly between treatments due to large fluctuations within each enclosure. The contents of TP SM and loosely adsorbed P in settling material decreased in the following order:–F/ + N > +F/ + N > –F/–N > +F/–N, indicating greater effects of nutrient addition than of food web structure. In sediments, organically bound P was 9–23% higher in–F variants compared to the corresponding +F treatments, thus indicating an effect of food web structure. Furthermore, positive correlations between SRP Epi , TP Epi , TP SM , TP Sed , sediment reductant-soluble P and calcite bound P revealed an effect of the epilimnetic P concentration on P sedimentation and specific P binding forms. Compared to the composition of different P binding forms in the settling material, a considerable decrease of loosely adsorbed P (12–26%) and reductant-soluble P (14–21%), as well as an increase of organic P (14–26%) were observed in the uppermost 1cm-layer of the sediments in all treatments. We conclude that both nutrient enrichment (+N) and food web structure (–F) enhance the P sedimentation and P content at the sediment surface. However, in addition to food web effects on organic P content in settling matter and sediments, factors like iron concentration and calcite precipitation might be of importance for P sedimentation and storage in sediments in complex systems such as lakes.

Dietary supply with essential lipids affects growth and survival of the amphipod Gammarusroeselii

Publication date: Available online 5 February 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): René Gergs , Nicole Steinberger , Timo Basen , Dominik Martin-Creuzburg
Growth and survival of benthic macroinvertebratesdepend on theavailabilityand the quality of potential food sources. The significance of essential biochemical nutrients, such as sterols and polyunsaturated fatty acids (PUFAs), for benthic invertebrates has been insufficiently studied. We investigated the effects of these essential lipids on growth and survival of the benthic gammarid Gammarusroeselii , a widespread species in streams, rivers and lentic waters of Central Europe,in standardized feeding experiments.Juvenile gammaridswere fed a mixture of three cyanobacteria with no evidence of toxin production, either unsupplemented or supplemented with cholesterol or the long-chain PUFA docosahexaenoic acid (DHA)using Bovine Serum Albumin (BSA)to load algal or cyanobacterial cells with single lipid, and a mixture of three eukaryotic algaecontainingvarious sterols and long-chain PUFAs.Our results revealed that growth and especially survival of gammarids on the cyanobacterial diet significantly increased upon supplementation with cholesterol and DHA, indicating that the nutritional inadequacy of cyanobacteria for gammarids and potentially other benthic invertebrates is at least partially due to a deficiency in these essential lipids. We propose that the expected increase in the frequency of pelagic cyanobacterial mass developments as a consequence of global warming will also affect benthic food web processesto anas yet unknown magnitude.

The role of food availability and phytoplankton community dynamics in the seasonal succession of zooplankton community in a subtropical reservoir

Publication date: Available online 1 February 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Chun-Wei Chang , Fuh-Kwo Shiah , Jiunn-Tzong Wu , Takeshi Miki , Chih-hao Hsieh
Seasonal patterns of zooplankton succession have been explained by physical factors such as temperature and precipitation. While the influence of biological factors, such as food availability and composition, has been recognized in theory, how food availability and composition affect the seasonal succession of zooplankton communities, especially in tropical/subtropical lakes, is still unclear and under debate. In this study, we applied multivariate analyses to a 3-year time series of physicochemical factors, various food sources (primary and bacterial production), and phytoplankton and zooplankton species composition in a subtropical reservoir in Taiwan. Our results demonstrated that (i) in addition to physical factors, seasonal variation of food availability partly explains zooplankton seasonal succession. In particular, inter-annual variation of food availability proved more important than physical factors in determining the inter-annual variation in the magnitude of seasonal succession. Specifically, limited food supply amplifies the magnitude of seasonal variation of zooplankton community biomass and composition; (ii) a stronger association between zooplankton and phytoplankton was found between their species composition rather than their biomass, implying a strong interaction between zooplankton and phytoplankton at the community level.

Effects of limnoecological changes on the Ostracoda (Crustacea) community in a shallow lake (Lake Çubuk, Turkey)

Publication date: Available online 30 January 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Okan Külköylüoğlu , Necmettin Sarı , Muzaffer Dügel , Şükran Dere , Nurhayat Dalkıran , Cem Aygen , Sırma Çapar Dinçer
We sampled Lake Çubuk, a shallow lake in Bolu (Turkey), for 26 months to investigate the effect of limnoecological changes on the composition of ostracod species. Seventeen ostracod species were identified from the six stations sampled between 2008 and 2010. Numbers of species and individuals were both significantly reduced during 2010, which corresponded to a 3 m water level increase. Ostracod Watch Model (OWM) displayed distinct seasonal occurrences of five species (Candona neglecta, Cypria ophtalmica, Cypridopsis vidua, Limnocythere inopinata, Fabaeformiscandona cf. japonica) when Physocypria kraepelini was the only species encountered all year round. Approximately 77.2% of the relationship between species and environmental variables was expressed by the first two axes of Canonical Correspondence analyses (CCA). Electrical conductivity and water temperature (P = 0.002) were the most influential variables on species. There was a significant negative correlation of seven species to conductivity. Of those, (F. cf. japonica and C. vidua) showed a significant positive correlation to water temperature, while C. candida was negatively correlated to water temperature (P < 0.05). Candona neglecta was the only species to show a positive correlation to dissolved oxygen. Tolerance limits for the most common species were higher than the mean water temperatures, but lower than mean levels of electrical conductivity. Finding the ratio of noncosmopolitan to cosmopolitan species “pseudorichness” as 1.13 suggested significant role of cosmopolitan species to species diversity.

Hydrological connectivity as most probable key driver of chlorophyll and nutrients in oxbow lakes of the Bug River (Poland)

Publication date: Available online 29 January 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Lech Kufel , Szymon Leśniczuk
Concentrations of chlorophyll, dissolved inorganic nitrogen and phosphorus, total phosphorus and suspended solids were analysed in 10 oxbow lakes of the Bug River in spring and summer. According to their connectivity with the river, all lakes were divided into 3 categories–lakes connected with the river channel but separated from the floodplain inputs, lakes connected with the river but receiving inputs from the floodplain and totally isolated lakes. Connected lakes showed significantly higher concentrations of available nutrients and chlorophyll but the relationship between the two variables was weak in the spring and non-existent in the summer. Suspended solids were also more abundant in connected than in isolated lakes. Analyses of the proportion of chlorophyll and particulate phosphorus in suspension led us to the conclusion that water movement in connected lakes inhibited sedimentation and kept algae in the water column. Isolated oxbow lakes devoid of wind-driven mixing were more susceptible to algal sedimentation which would explain the differences observed between the two lake categories.

No differences between littoral fish community structure of small natural and gravel pit lakes in the northern German lowlands

Publication date: Available online 10 January 2014
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Matthias Emmrich , Svenja Schälicke , Daniel Hühn , Christian Lewin , Robert Arlinghaus
Habitat loss has been identified as a major contributor to declining freshwater biodiversity, resulting in a high thread level among European fishes. Non-natural ecosystems such as pit lakes may compensate habitat loss by providing new habitat for aquatic organisms. We compared the structure of the littoral fish communities of 18 natural and 19 gravel pit lakes located in the northern German lowlands to evaluate whether artificial lakes managed by angling clubs host similar communities as typically observed in natural lakes. The fish community structure was analyzed between the lake types and along gradients of lake morphometry, productivity and littoral complexity. Although the gravel pit lakes differed in morphology (characterized by steeper littoral slopes and less structured littoral habitat), differences in fish community structure between the natural and gravel pit lakes were weak and mainly related to differences in the abundance of the dominant species perch, roach and rudd. Both lake types had similar species richness, community diversity and hosted several small-bodied and endangered species. To conclude, fish communities characteristic of small natural lakes may serve as reference for the development of gravel pit lakes. Moreover, our study reveals that recreational-fisheries management of gravel pit lakes does not result in artificial communities that deviate strongly from the communities present in natural lakes. Therefore, nature conservation and fisheries management goals can be reconciled in relation to fish in small artificial lakes managed by angling clubs.

Fish assemblages in forest drainage ditches: degraded small streams or novel habitats?

Publication date: Available online 30 December 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Raul Rosenvald , Rein Järvekülg , Asko Lõhmus
Artificial drainage of forested wetlands to increase timber production has profoundly altered the hydrology of North-European landscapes during the 20th century. Nowadays, drainage ditches and small dredged streams can comprise most fluvial water bodies there, but the resulting ecological effects are poorly documented. In the current study, we explored, using fish as an indicator group, consequences of the transformation of natural stream networks to a mixture of natural and artificial watercourses. We asked whether the transformation results in impoverishment, enrichment or re-assembling of the communities both at watercourse and the landscape scales. We sampled fish in 98 sites in five well-forested regions in Estonia where ditches formed 83–92%, dredged streams 4–7%, and natural streams 3–10% of the total length of small watercourses. Based on a total of 6370 individual fish of 20 species, we found that, compared to natural streams, ditches had an impoverished fauna at both scales and both in terms of species richness and assemblage composition. Only natural streams hosted characteristic species (with Barbatula barbatula , Lampetra planeri and Lota lota emerging as significant indicators), while dredged streams had intermediate assemblages. The habitat factors explaining those drainage-related differences included a reduced flow velocity, loss of stream channel variability, less transparent water, and abundant aquatic vegetation. Hence, for stream-dwelling fish, drained forest landscapes represent degraded habitats rather than novel ecosystems, which contrasts with the transformation of terrestrial assemblages. Future studies should address whether that reflects the situation for whole aquatic assemblages, and how is the functioning of the hydrological systems affected. We suggest that the critical management issues for environmental mitigation of ditching effects on fish include basin scale spatial planning, protecting of the remaining natural streams, and rehabilitation of ditch channels in flat landscapes lacking beavers.

Aquatic Coleoptera distribution patterns and their environmental drivers in central Portugal, Iberian Peninsula

Publication date: Available online 30 December 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Amaia Pérez-Bilbao , Ana Raquel Calapez , Maria João Feio
Here, we present the distribution patterns of aquatic Coleoptera species collected in Central Portugal (240 samples, 136 stream sites) and their most important environmental drivers. A total of 81 species were identified from which 16 were endemic of the Iberian Peninsula confirming the high species richness and importance for conservation of this area. The families with higher species richness were Dytiscidae (24 species), Hydraenidae (16 species), Elmidae (13 species) and Hydrophilidae (12 species). We found six groups mainly based on altitudinal, conductivity and lithology gradients. We found a replacement of families, filling different niches over the catchments environmental gradients. According to the distribution maps, the families Dytiscidae and Hydrophilidae appeared in lowland streams while Hydraenidae were collected in upper stretches of the rivers. Various species appeared widely distributed along the different watersheds, most of them belonging to the families Elmidae and Hydraenidae. The highest species richness was found for the Hydraena , represented by 13 species in our study area. Some Hydraena species tend to co-occur at the same sites and have a high similarity in their distribution. This first study of ecological patterns of Coleopteran species in Portugal brought thus new insights to knowledge of this invertebrate group.

Population traits of invasive bleak Alburnus alburnus between different habitats in Iberian fresh waters

Publication date: Available online 24 December 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): David Almeida , Paris V. Stefanoudis , David H. Fletcher , Carlos Rangel , Eduardo da Silva
The bleak Alburnus alburnus (L.) is a cyprinid native to most of Europe, mainly inhabiting lentic environments. This fish species is a successful invader in the Iberian Peninsula, where it was first introduced to reservoirs as forage fish during the 1990s. Bleaks threaten the highly endemic Iberian fish fauna by means of trophic competition and hybridization. Yet, little is known about the environmental biology of bleaks in the Iberian Peninsula, particularly far from impounded waters. Thus, the aim of this work was to compare seasonal and gender variation of size structure, body condition and reproductive investment of bleaks between different habitats. Only sexually mature bleaks were seasonally collected and examined from the River Gévora and the Sierra Brava Reservoir (southwestern Spain) to assess more in-depth the adaptive capacity at the population level and the subsequent invasiveness. Bleak was an abundant species in the fish assemblages of both habitat types (i.e. river and reservoir). The proportion of smaller mature bleaks was lower in the river than the reservoir during spring and the opposite pattern was observed during winter. Both male and females were larger in the river during the breeding season in the study areas (i.e. spring), as well as with higher body condition and reproductive investment. These findings suggest that bleaks enhance their reproduction rate in the river to compensate for higher mortality in this habitat, where environmental conditions may be harsher due to the winter floods and summer droughts typical of Mediterranean water courses. Overall results highlight the high degree of plasticity in population traits of the bleak in the Iberian Peninsula, which will surely aid its ability to adapt to a wide variety of Mediterranean ecosystems, including lentic and lotic environments. Consequently, this invasive fish may pose a serious risk for the highly valuable fauna of Mediterranean Europe.

Response of fish and benthic invertebrate communities to constrained channel conditions in a mountain river: Case study of the Biała, Polish Carpathians

Publication date: Available online 21 December 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Bartłomiej Wyżga , Antoni Amirowicz , Paweł Oglęcki , Hanna Hajdukiewicz , Artur Radecki-Pawlik , Joanna Zawiejska , Paweł Mikuś
Following considerable hydromorphological degradation in past decades, the gravel-bed Biała River, Polish Carpathians, is to be restored through establishing erodible corridor in two river sections. In these sections, relatively long, unmanaged channel reaches alternate with short, channelized reaches located in the vicinity of bridges. Effects of the alternating morphologies on physical habitat conditions, fish and benthic invertebrate communities, and ecological river quality were investigated in 10 pairs of unmanaged and channelized cross-sections located between significant tributaries. Unmanaged cross-sections with an average of two low-flow channels exhibited significantly greater variation in depth-averaged and near-bed velocity and bed material size than single-thread, channelized cross-sections. Summer, autumn and winter surveys of benthic invertebrates indicated that the unmanaged cross-sections typically hosted three times more taxa than channelized cross-sections, and this was reflected in distinct appraisal of the two cross-section types by means of invertebrate-based BMWP-PL index. Electrofishing indicated no statistically significant difference in the number of fish species between both types of river cross-sections, and the resultant similar scores of the European Fish Index allowed both cross-section types to be associated with the same class of ecological river quality. This study indicated that short channelized river reaches do not disrupt continuity of fish populations, although they provide worse habitats for fish, reflected in the lower numbers of individuals, especially juveniles. It also highlighted the need of investigating various groups of river biota to determine the response of river biocoenosis to environmental stressors and evaluate the ecological status of the river.

Diet of two invading gobiid species (Proterorhinus semilunaris and Neogobius melanostomus) during the breeding and hatching season: no field evidence of extensive predation on fish eggs and fry

Publication date: Available online 16 December 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Mojmír Vašek , Lucie Všetičková , Kevin Roche , Pavel Jurajda
One of the potential impacts of invasive gobies on native fish fauna is predation on eggs and fry. Therefore, the diet composition of two invading gobiid species, the tubenose goby Proterorhinus semilunaris and round goby Neogobius melanostomus, was examined in the Dyje river system (Danube basin, Central Europe) during the 2011 reproductive season to ascertain the extent of gobiid predation on heterospecific and conspecific eggs and juveniles. Consumption of fish eggs and juveniles by invading gobies was very low. The diets of both species consisted largely of benthic macroinvertebrates, and particularly insect larvae. These results indicate that invading gobies in the Dyje river system are likely to impact native fish fauna more through competitive effects than through direct predation on eggs and juveniles.

Key drivers for phytoplankton composition and biomass in an Ethiopian highland Lake

Publication date: Available online 14 December 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Tadesse Fetahi , Michael Schagerl , Seyoum Mengistou
We studied the temporal phytoplankton community pattern of the deep crater lake Hayq in the highlands of Ethiopia from October 2007 to October 2008. Earlier sporadic surveys indicated that the phytoplankton community was predominantly characterized by heavy diatoms, which characteristically suffer from rapid sedimentation. The trophic status of Lake Hayq was reported to have changed from oligotrophic to eutrophic in 1992. The present study addresses the potential reasons for the diatom dominance as well as causes of the trophic change. Net and integrated water samples were used for determination of physico-chemical parameters and phytoplankton biovolumes. Our results revealed that diatoms and chlorophytes dominated during most of the study period in Lake Hayq and seem to be favored by the mixing regime of the water body, which can be described as partial atelomixis with daily mixing of the epilimnion maintaining the algae within the euphotic depth via regular re-suspension. However, the epilimnion may be decoupled from the hypolimnion by a seasonal chemocline. Nutrients were not limiting in the lake with an overall mean concentration of soluble reactive phosphorus of 22 μg L−1 and total phosphorus of 58 μg L−1 and of dissolved inorganic nitrogen of 305 μg L−1, with ammonium being the primary form. In the 1940-ies only diatoms were reported, but since the 1990’s other phytoplankton groups and taxa have become relevant. Canonical correspondence analysis showed that chlorophytes were mainly associated with nutrients and rainfall, euglenophytes with elevated alkalinity and the diatoms with silica and zooplankton. Chlorophyll a as measure of total phytoplankton biomass was significantly influenced by seasonality and underwater light supply, reflecting the significant role of atelomixis in persistent occurrence of heavy taxa in the epilimnion. The lake is still categorized as a eutrophic system, demonstrating that the trophic change reported in 1992 was not short-lived. In addition to changes in the catchment the eutrophication process was probably primarily triggered by a previous introduction of Tilapia in the lake, causing a cascading effect in the food-web interactions. This implied that the phytoplankton composition and biomass of this tropical deep tropical lake can be controlled through biomanipulation, as has been demonstrated for temperate lakes.

Shading effects on community composition and food web structure of a deforested pasture stream: evidences from a field experiment in Brazil

Publication date: Available online 12 December 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Mônica Ceneviva-Bastos , Lilian Casatti
Experimental manipulations in the field can evidence cause-effect relations from the manipulated variables. In this context, the aim of the present study was to investigate the effects of shading on stream community composition and food web structure. The experiment was conducted in two reaches of a pasture stream: one that remained open (control) and another that was covered with 75% factor shading cloth (treatment), sampled before and after 21 months. At each sampling, algae, macrophytes, plankton, meiofauna, macroinvertebrates, and fish were collected. All heterotrophic organisms were submitted to diet analysis and dietary data was used to calculate food web parameters. Community composition was evaluated through cluster analysis. A total of 7,556 individuals of 148 taxa was identified. The control reach presented lower richness, abundance, and food web parameter values than the treated reach before shading cloth installation, whereas after the experiment the opposite was observed. Despite these differences, both reaches had changed over the experimental period for being under increased siltation as a result of long term land use effects, which resulted in higher similarity of community composition between periods than between treatments. This observation was corroborated by higher food web complexity before the experiment, with decreases in all food web parameters (except connectance) after the 21 months, especially in the treated reach. Hence, decreases in community attributes and food web parameters after the experiment evidenced the effects of siltation, while the strongest decreases observed at the treated reach evidenced the effects of shading. Finally, we stress that the artificial shading itself does not promote allochthonous materials inputs (which add up to food web basis and promote habitat heterogeneity), so full-canopy riparian forest restoration is of fundamental importance for low-order streams.

Predicting Presence and Absence of Trout (Salmo trutta) in Iran

Publication date: Available online 12 December 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Hossein Mostafavi , Florian Pletterbauer , Brian W. Coad , Abdolrassoul Salman Mahini , Rafaela Schinegger , Günther Unfer , Clemens Trautwein , Stefan Schmutz
Species distribution modelling, as a central issue in freshwater ecology, is an important tool for conservation and management of aquatic ecosystems. The brown trout (Salmo trutta) is a sensitive species which reacts to habitat changes induced by human impacts. Therefore, the identification of suitable habitats is essential. This study explores the potential distribution of brown trout by a species distribution modelling approach for Iran. Furthermore, modelling results are compared to the distribution described in the literature. Areas outside the known distribution which may offer potential habitats for brown trout are identified. The species distribution modelling was based on five different modelling techniques: Generalised Linear Model, Generalised Additive Model, Generalised Boosting Model, Classification Tree Analysis and Random Forests, which are finally summarised in an ensemble forecasting approach. We considered four environmental descriptors at the local scale (slope, bankfull width, wetted width, and elevation) and three climatic parameters (mean air temperature, range of air temperature and annual precipitation) which were extracted on three different extents (1/5/10 km). The performance of all models was excellent (≥0.8) according to the TSS (True Skill Statistic) criterion. Slope, mean and range of air temperature were the most important variables in predicting brown trout occurrence. Presented results deepen the knowledge about distribution patterns of brown trout in Iran. Moreover, this study gives a basic background for the future development of assessment methods for riverine ecosystems in Iran.

Food webs of the Paraná River floodplain: assessing basal sources using stable carbon and nitrogen isotopes

Publication date: Available online 11 December 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Mercedes Rosa Marchese , Miguel Saigo , Florencia Lucila Zilli , Soledad Capello , Melina Devercelli , Luciana Montalto , Graciela Paporello , Karl Matthias Wantzen
Food webs in floodplain ecosystems may be based on a variety of aquatic, terrestrial or amphibious food resources. Here, we determined which of the basal resources mostly contribute to the food webs in a floodplain lake of the Middle Paraná River using isotopic composition of C and N (δ13 C and δ15 N) of potential food sources in the Paraná floodplain (Argentina). We analyzed if organic matter sources isotope of C and N differ between flooding and low water seasons, and analyzed the isotopic niche representations of consumers in order to characterize niches width and intraguilds overlapping. To estimate the contribution of different sources of carbon to primary consumers, we measured the stable isotopic compositions of bottom sediment organic matter, coarse particulate organic matter, biofilm, suspended particulate organic matter, epiphyton, phytoplankton, C3 and C4 macrophytes and riparian tree leaves, benthic macroinvertebrates, aquatic orthopterans and fishes in dry and flooding seasons. The packages Stable Isotope Analysis and the Stable Isotope Bayesian Ellipses algorhythm in R were calculated to compare the C and N isotopic variability between the primary consumers and their sources. The energy sources available for benthic organisms mainly originated from autochthonous sources based on the C3 photosynthesis pathway. The isotopic signatures of sources and primary consumers did not differ significantly between low and high water seasons. Our results demonstrated a higher contribution to primary consumers of C3 macrophytes and low contributions of C4 for herbivores; biofilm and benthic organic matter for gatherer collectors (Oligochaeta and Chironominae); epiphyton for ephemeropterans, amphipods and fishes, whereas biofilm was the most important source for mussels.

Leaf litter decomposition in remote oceanic islands: the role of macroinvertebrates vs microbial decomposition of native vs exotic plant species

Publication date: Available online 22 November 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Pedro Miguel Raposeiro , Gustavo Martins , Isadora Moniz , Andreia Cunha , Ana Cristina Costa , Vitor Gonçalves
Freshwater communities on remote oceanic islands can be depauperate due to the influence of biogeographic processes that operate over a range of spatial scales, influencing the colonization of organisms, and events that shape local freshwater assemblages. The consequences of this paucity in organism diversity for the functioning of these ecosystems are, however, not well understood. Here, we examine the relative decomposition rate of leaf litter of native vs. exotic origin by aquatic macroinvertebrates and microbial communities in an isolated and depauperate oceanic environment. Bags containing a standard amount of leaf litter of each of 10 tree species (5 native and 5 non-native species) were deployed on two streams. Two types of bags differing in mesh size were used to allow or prevent the access of leaf litter to macroinvertebrates, respectively. Over a period of 28 days, mass loss of leaf litter was similar in the two bag types suggesting that macroinvertebrates had little influence on the break down of leaf litter in this system. In addition, there was no difference in mass loss of leaf litter of native and exotic origin. Decomposition rates were highly species-specific suggesting that decomposition rates were related to inhibitory substance specific of each leaf species. Our results add to the wider literature by showing that in depauperate and isolated ecosystems, and in contrast to temperate continental ecosystems, decomposition of plant litter by aquatic macroinvertebrates is negligible.

Flight distance of mosquitoes (Culicidae): A metadata analysis to support the management of barrier zones around rewetted and newly constructed wetlands

Publication date: Available online 20 November 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Piet F.M. Verdonschot , Anna A. Besse-Lototskaya
Society responds to changes in climate and land use via mitigation measures, including rainwater retention and storage in rewetted and newly constructed wetlands. Humans living close to these wetlands express concerns about future mosquito nuisance situations, and request the necessary distance between human occupation and wetlands to avoid such problems. Wetland managers need to know the distance required, as well as the type of management needed for such buffer or barrier zones. Here we performed an extensive literature survey to collect quantitative information on mosquito flight distance and the relevant environmental conditions. Mosquitoes have an average maximum flight distance of between 50 m to 50 km, depending on the species. Long-distance or migratory flights are strongly related to species ecological preferences and physiology, are survived by few specimens, and do not relate to nuisance situations. Nuisance-related or non-oriented flights are also species-specific and cover much shorter distances-between 25 m and 6 km for the 23 species analyzed. Based on these results, we made regression-based estimations of the percentages of the population that cross certain distances. A 90% reduction in breeding site population density would require minimal distances of 56 m for Anopheles saperoi and 8.6 km for Anopheles sinensis, and much greater distances for Aedes vexans, Culex quinquefasciatus, and Culiseta morsitans. Little useful information was available regarding the environmental conditions under which non-oriented flights took place. Qualitatively, the review showed that flight capacity was influenced by landscape structure, meteorological conditions (temperature, humidity, and illumination), and species physiology (energy available for flight). Overall, our findings suggest that predictions regarding the construction of barrier zones around breeding sites can be made based on mosquito and host density and human nuisance perception, and that barrier zone usefulness strongly depends on the mosquito species involved. Additional quantitative research is needed to better document the non-oriented dispersal patterns of the mosquitoes that populate rewetted and newly constructed wetlands, and the effects of vegetation types in barrier zones on mosquito densities.

COLONISATION OF LOW- AND HIGH-QUALITY DETRITUS BY BENTHIC MACROINVERTEBRATES DURING LEAF BREAKDOWN IN A SUBTROPICAL STREAM

Publication date: Available online 20 November 2013
Source:Limnologica – Ecology and Management of Inland Waters
Author(s): Rodrigo König , Luiz Ubiratan Hepp , Sandro Santos
Leaf litter in streams is exploited by benthic macroinvertebrates, and leaf traits may influence colonisation by this group. This study aimed to compare the leaf decomposition rates, structure, and composition of the macroinvertebrate fauna colonising the litter of plant species with contrasting leaf traits. Litter bags from two native plant species ( Sebastiania brasiliensis and Campomanesia xanthocarpa ) and two non-natives ( Hovenia dulcis and Platanus × acerifolia ) were incubated in a subtropical stream. After 7, 14, 21, and 28 days, four leaf bags for each species were removed, and the leaf decomposition rates, density of organisms and trophic guilds, taxonomic richness, and functional composition of the macroinvertebrates were compared. The decomposition rates and densities of organisms, shredders, and collector-gatherers were higher for the leaves considered to be better quality, with lower C:N and Lignin:N ratios (from S. brasiliensis and H. dulcis ). Additionally, the taxonomic and functional compositions of the macroinvertebrates were different for these leaves. In contrast, the species richness and density of the other guilds showed no significant difference between species. This study shows that detritivorous groups prefer leaves of better quality, and most results may be influenced by the high nutritional content and low amount of compounds that complicate fragmentation, such as tannins, lignin, and cellulose. Therefore, the effects of the replacement of riparian plant species on the local macrofauna depend of the traits of the introduced and replaced plant, regardless of their origin