Influence of fish assemblage and shallow lake productivity on waterfowl communities in the Boreal Transition Zone of western Canada

1. Shallow lakes in the Boreal Transition Zone (BTZ) in Alberta, Canada are naturally productive systems that provide important breeding and moulting habitat for many waterfowl (Anseriformes). To examine the relative importance of biotic and abiotic factors on waterfowl population densities, species richness and community composition, we surveyed 30 shallow lakes and evaluated the relationships among fish communities, lake characteristics and waterfowl in both breeding and moulting habitat. Shallow lakes were either fishless (n = 15), contained only small‐bodied fishes (n = 10) or contained large‐bodied, mostly predatory, fish in addition to small‐bodied fish (n = 5). 2. Environmental factors, including water colour, submerged aquatic vegetation, lake area and potassium, explained 24.3% of the variation in breeding waterfowl communities. Fish assemblage contributed independently to a small but significant proportion (13.4%) of the variation, while 13.8% of the explained variation was shared between environmental factors and fish assemblage. In total, 51.5% of the variation in breeding waterfowl communities was explained. 3. Overall, 55.5% of the total variation in moulting waterfowl communities was explained. Environment alone [especially total phosphorus, lake area, maximum depth and dissolved organic carbon (DOC)] and variation shared by fish and environment similarly accounted for most of the explained variation in moulting waterfowl communities (21.7% and 25.7% respectively), while fish assemblage was only one‐third as important (8.1%). 4. Both breeding and moulting waterfowl densities increased with lake productivity, even in eutrophic and hypereutrophic lakes. Breeding waterfowl density was also twice as great in fishless lakes than in lakes with fish, after accounting for lake area. 5. Certain waterfowl taxa were linked to fishless lakes, especially in the moulting season. Canvasback and moulting ring‐necked ducks were linked to small‐bodied fish lakes, whereas moulting common goldeneye were indicators of large‐bodied fish lakes. Knowledge of fish presence and species composition can therefore help guide conservation and management of waterfowl habitat in western Canada. Our results suggest that management efforts to maintain the most productive waterfowl habitat in the BTZ should focus on smaller, shallow, fishless lakes, particularly given that larger fish‐bearing systems have greater regulatory protection.     

An Analysis of Fish Species Richness in Natural Lakes

There is a growing recognition of the need to conserve biodiversity that has been conceptualised in the Convention of Biological Diversity. Maintenance of fish species richness is particularly important, because habitat degradation in inland waters continues to accelerate on a global scale. Here we develop empirical models for predicting fish species richness in natural lakes in various geographical regions of the world. In tropical lakes where fish biodiversity is richer than in temperate lakes, fish species richness can be predicted by a few variables such as lake area and altitude. Low fish species richness in most temperate lakes might be due to the effect of glaciation on colonisation and speciation of fishes. In US, Canadian and northern European lakes, lake acidification is one of the important factors influencing fish species richness. Although limnological characteristics influence fish species richness in temperate lakes, lake area and altitude have greater predictive power. This is in contrast to fish species richness in rivers, which can be reliably predicted by basin area. In the power curves, which describe the relationship between fish species richness and habitat size in lakes and rivers, the exponent is always greater in tropical regions than in temperate regions. Because fish biodiversity is greater in the tropics threats to fish biodiversity through habitat degradation are greater than those in temperate inland waters.     

Lakes and rivers as islands: species-area relationships in the fish faunas of Ontario

Synopsis Fish species richness in 82 lakes in Ontario, Canada was significantly correlated with surface area. In this region, latitude explained only a small amount of the variation in fish species richness. Thus, our study provides a clear demonstration of the relation between fish species richness and lake area without the confounding effects of latitude and physiography inherent in analyses from broader geographic regions. By comparison with the species-area relationship obtained, we show that acidification clearly depressed the number of fish species in 66 acid-stressed lakes in Ontario. Fish species richness was also significantly correlated with both drainage and surface areas of 21 Ontario rivers. Slopes of species-area regressions of lakes and rivers did not differ significantly, suggesting that species are added to these habitats at similar rates. However, our regression analyses show that rivers support more species of fish per unit surface area of water. Although these results are consistent with some predictions of island biogeography theory, we suggest that fish species richness is more likely to be a simple function of habitat diversity, rather than an equilibrial balance between immigration and extinction.     

Patterns and Potential Drivers of Dramatic Changes in Tibetan Lakes, 1972–2010

Most glaciers in the Himalayas and the Tibetan Plateau are retreating, and glacier melt has been emphasized as the dominant driver for recent lake expansions on the Tibetan Plateau. By investigating detailed changes in lake extents and levels across the Tibetan Plateau from Landsat/ICESat data, we found a pattern of dramatic lake changes from 1970 to 2010 (especially after 2000) with a southwest-northeast transition from shrinking, to stable, to rapidly expanding. This pattern is in distinct contrast to the spatial characteristics of glacier retreat, suggesting limited influence of glacier melt on lake dynamics. The plateau-wide pattern of lake change is related to precipitation variation and consistent with the pattern of permafrost degradation induced by rising temperature. More than 79% of lakes we observed on the central-northern plateau (with continuous permafrost) are rapidly expanding, even without glacial contributions, while lakes fed by retreating glaciers in southern regions (with isolated permafrost) are relatively stable or shrinking. Our study shows the limited role of glacier melt and highlights the potentially important contribution of permafrost degradation in predicting future water availability in this region, where understanding these processes is of critical importance to drinking water, agriculture, and hydropower supply of densely populated areas in South and East Asia.     

Species richness and distribution of eastern Australian lake chironomids and chaoborids

1. Chironomids and chaoborids were collected across eastern Australia and Tasmania in dune, glacial, sinkhole and maar lakes. Based on sampling exuviae from these relatively undisturbed freshwater lakes, we observed that species richness on the Australian continent was substantially greater than previously reported, and challenge the long‐standing view that chironomid species richness is depauperate in Australian lakes, compared with the northern hemisphere. 2. While chironomid species richness was equivalent across the four geographical regions sampled (tropical northern Queensland, Fraser Island, south‐eastern mainland Australia and Tasmania), there were only five ‘cosmopolitan’ species found across all regions. In general, species distributions were more closely associated with geographical region than with lake characteristics, and there were species assemblage differences among biogeographical regions. More than half of the 134 identified species were restricted to a single geographical region. Overall, Tasmanian lakes had the highest proportion of locally endemic species. 3. Latitude and altitude more strongly influenced species assemblages than did lake chemistry, although species richness sometimes varied among lake geomorphic types within a region.     

Development of a Fish Based Lake Typology for Natural Austrian Lakes >50 ha Based on the Reconstructed Historical Fish Communities

Based on the reconstructed native fish communities all natural Austrian lakes >50 ha (n = 43) were classified into four groups using cluster analysis methods. Sentinel species (i.e. species with highest discriminating value for lake types and characteristic for a specific lake group) and type specific fish species (accompanying species with additional value for characterising lake groups) were defined by a newly developed index and by similarity analysis. The first group included 16 lakes of high altitude, small surface area and low fish species number with arctic char as a sentinel species. The second group (n = 10) was characterized by intermediate altitude, large surface area and high maximum water depth with the minnow as sentinel species. The third group contained 14 lakes with low maximum water depths and a long retention time. For this group the bleak was found as a sentinel species. The lakes of the eastern part of Austria represented the last group (n = 3) and were characterized by low altitude and very shallow water depth with pike‐perch as a sentinel species. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Homogenization of fish assemblages in different lake depth strata at local and regional scales

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Is the island biogeography model a poor predictor of biodiversity patterns in shallow lakes?

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Rotifer species richness along an altitudinal gradient in the Alps

Aim Biodiversity patterns along altitudinal gradients are less studied in aquatic than terrestrial systems, even though aquatic sites provide a more homogeneous environment independent of moisture constraints. We studied the altitudinal species richness pattern for planktonic rotifers in freshwater lakes and identified the environmental predictors for which altitude is a proxy. Location Two hundred and eighteen lakes of Trentino–South Tyrol (Italy) in the eastern Alps; lakes covered 98% (range 65–2960 m above sea level) of the altitudinal gradient in the Alps. Methods We performed: (1) linear regression between species richness and altitude to evaluate the general pattern, (2) multiple linear regression between species richness and environmental predictors excluding altitude to identify the most important predictors, and (3) linear regression between the residuals of the best model of step (2) and altitude to investigate any additional explanatory power of altitude. Selection of environmental predictors was based on limnological importance and non‐parametric Spearman correlations. We applied ordinary least squares regression, generalized linear, and generalized least squares modelling to select the most statistically appropriate model. Results Rotifer species richness showed a monotonic decrease with altitude independent of scale effects. Species richness could be explained (R²= 51%) by lake area as a proxy for habitat diversity, reactive silica and total phosphorus as proxies for productivity, water temperature as a proxy for energy, nitrate as a proxy for human influence and north–south and east–west directions as covariates. These predictors completely accounted for the species richness–altitude pattern, and altitude had no additional effect on species richness. Main conclusions The linear decrease of species richness along the altitudinal gradient was related to the interplay of habitat diversity, productivity, heat content and human influence. These factors are the same in terrestrial and aquatic habitats, but the greater environmental stability of aquatic systems seems to favour a linear pattern.     

Surface water connectivity drives richness and composition of Arctic lake fish assemblages

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Lake size and fish diversity determine resource use and trophic position of a top predator in high‐latitude lakes

Prey preference of top predators and energy flow across habitat boundaries are of fundamental importance for structure and function of aquatic and terrestrial ecosystems, as they may have strong effects on production, species diversity, and food‐web stability. In lakes, littoral and pelagic food‐web compartments are typically coupled and controlled by generalist fish top predators. However, the extent and determinants of such coupling remains a topical area of ecological research and is largely unknown in oligotrophic high‐latitude lakes. We analyzed food‐web structure and resource use by a generalist top predator, the Arctic charr Salvelinus alpinus (L.), in 17 oligotrophic subarctic lakes covering a marked gradient in size (0.5–1084 km²) and fish species richness (2–13 species). We expected top predators to shift from littoral to pelagic energy sources with increasing lake size, as the availability of pelagic prey resources and the competition for littoral prey are both likely to be higher in large lakes with multispecies fish communities. We also expected top predators to occupy a higher trophic position in lakes with greater fish species richness due to potential substitution of intermediate consumers (prey fish) and increased piscivory by top predators. Based on stable carbon and nitrogen isotope analyses, the mean reliance of Arctic charr on littoral energy sources showed a significant negative relationship with lake surface area, whereas the mean trophic position of Arctic charr, reflecting the lake food‐chain length, increased with fish species richness. These results were supported by stomach contents data demonstrating a shift of Arctic charr from an invertebrate‐dominated diet to piscivory on pelagic fish. Our study highlights that, because they determine the main energy source (littoral vs. pelagic) and the trophic position of generalist top predators, ecosystem size and fish diversity are particularly important factors influencing function and structure of food webs in high‐latitude lakes.     

Presence of fish affects lake use and breeding success in ducks

Several previous studies indicate that presence of fish has negative effects on waterbirds breeding on lakes, owing either to competition for common invertebrate prey or fish predation on ducklings/chicks. However, others have reported results to the contrary and it remains unresolved what factors trigger, inhibit, and modulate fish–waterbird interactions. The present study was designed to test the effect of fish presence per se, with a minimum of variation in possibly confounding environmental variables. Thus, after stratifying for area, depth, altitude, pH, and total phosphorus we compared 13 lakes with and 12 without fish (mainly pike Esox lucius and perch Perca fluviatilis) with respect to (i) general species richness of waterbirds, (ii) species-specific utilization and breeding success of two dabbling ducks (mallard Anas platyrhynchos and teal Anas crecca) and a diving duck (goldeneye Bucephala clangula). General species richness of waterbirds was higher on fishless lakes. Overall use (bird days) and brood number of teal and goldeneye were higher on fishless lakes. The latter also had more benthic and free-swimming prey invertebrates compared to lakes with fish. Mallard use, mallard brood number, and abundance of emerging insects did not differ between lake groups. Generalized linear models including fish presence as factor and considering seven environmental variables as covariates, confirmed that all waterbird variables except mallard days and broods were negatively correlated to fish presence. There was also a residual positive relationship of lake area on general species richness, teal days, and teal broods. Our data demonstrate a stronger effect of fish presence on diving ducks and small surface feeding ducks than on large surface-feeding ducks. We argue that observed patterns were caused by fish predation on ducks rather than by fish–duck competition for common prey.     

Lake depth and geographical position modify lake fish assemblages of the European 'Central Plains' ecoregion

1. Classification of European lake fish assemblages can be based on fish‐assemblage structure or morphological, geographical, physical and chemical lake attributes. However, substantial gaps in knowledge exist with respect to the correspondence between both classification approaches. 2. Here, we compiled fish assemblage data from 165 lakes situated in the European ‘Central Plains’ ecoregion. Cluster analysis of fish abundances was performed to compare fish assemblage types of the entire ecoregion with those from previous country‐specific studies. Nonparametric group comparisons, classification trees and partial canonical ordinations were used to infer the correspondence between fish assemblage types and morphology, geographical position and nutrient concentration of the lakes. 3. Three distinct fish assemblages were revealed: vendace (Coregonus albula), ruffe (Gymnocephalus cernuus) and roach (Rutilus rutilus) lake types. Both latitude and lake depth were the best determinants of lake type, but total phosphorus (TP) concentrations were also important. Vendace lakes were deep and had low TP concentrations, whereas the shallower ruffe and roach lakes had higher TP values. Roach lakes were more frequent in the north‐west area of the ecoregion, whereas ruffe lakes were more often found south of the Baltic Sea. 4. Controlling for the influence of nutrient concentration showed that lake morphology and geographical position were important determinants of fish assemblages. However, the variance explained was low (<20%), implying that biological interactions may also be important in forming the lake‐specific fish assemblages. 5. The results suggest that fish assemblages differ between deep and shallow lakes, and between the north‐west and south‐east locations within the Central Plains ecoregion. Accordingly, establishment of depth‐related lake morphotypes is needed, and the European ecoregions recommended to be used in evaluation systems according to the Water Framework Directive seem to be too coarse to reflect the subtle differences of fish species richness along geographical gradients.     

Native and introduced fish species richness in French lakes: local and regional influences

Aim To analyse the importance of local and regional influences on the patterns of species richness in natural and man‐made lakes and to infer the impacts of human‐mediated introductions on these patterns. Location France. Methods Species occurrence data were gathered for 25 natural and 51 man‐made lakes. Analysis is based on regression models of local richness against their related regional richness and lake environmental variables. Results Local native richness was mostly controlled by the regional richness. Conversely, local total richness was mainly explained by local variables. These statements apply to both natural and man‐made lakes. Lacustrine systems displayed weak resistance to invaders. Main conclusions Species introductions have apparently contributed to saturate fish communities in these systems even if no clear negative effect on the survival of native species (i.e. species extinction) is detectable so far.     

The role of environmental and spatial processes in structuring native and non‐native fish communities across thousands of lakes

Quantifying the role of spatial patterns is an important goal in ecology to further understand patterns of community composition. We quantified the relative role of environmental conditions and regional spatial patterns that could be produced by environmental filtering and dispersal limitation on fish community composition for thousands of lakes. A database was assembled on fish community composition, lake morphology, water quality, climatic conditions, and hydrological connectivity for 9885 lakes in Ontario, Canada. We utilized a variation partitioning approach in conjunction with Moran's Eigenvector Maps (MEM) and Asymmetric Eigenvector Maps (AEM) to model spatial patterns that could be produced by human‐mediated and natural modes of dispersal. Across 9885 lakes and 100 fish species, environmental factors and spatial structure explained approximately 19% of the variation in fish community composition. Examining the proportional role of spatial structure and environmental conditions revealed that as much as 90% of the explained variation in native species assemblage composition is governed by environmental conditions. Conversely on average, 67% of the explained variation in non‐native assemblage composition can be related to human‐mediated dispersal. This study highlights the importance of including spatial structure and environmental conditions when explaining patterns of community composition to better discriminate between the ecological processes that underlie biogeographical patterns of communities composed of native and non‐native fish species.     

Classification of the Tatra Mountain lakes (Slovakia) using chironomids (Diptera,Chironomidae)

Chironomid assemblages in thirty-three mountain lakes situated above tree line in the Slovakian part of the Tatra Mountains were studied during 2000–2002. Chironomid species/taxa, collected as pupal exuviae, were correlated with physical, chemical, and lake morphometry variables of 22 lakes. Two-way indicator species analysis (TWINSPAN) was used to classify the lakes into four distinct groups: higher situated alpine lakes, lower situated alpine lakes, subalpine lakes and acidified lakes. Presence/absence of eight taxa was identified as indicative for this classification. In discriminant function analysis, pH, dissolved organic carbon, altitude and lake area were the most significant variables reflecting differences among groups of lakes. This model of four variables allowed 77% success in the prediction of group membership. A multiple regression model with lake area, concentration of magnesium and total phosphorus accounted for 37% of the variance in taxa richness. Lakes with greater area contained more chironomid taxa than smaller ones. Lakes with higher alkalinity and higher trophic status tend to support more taxa. Canonical correspondence analysis (CCA) indicated that most variation in the composition of chironomid assemblages was related to pH and to altitude. The results can be used as reference data for long-term monitoring of the Tatra lakes, especially in connection with a recovery from acidification and global climatic change.     

Intraspecific phenotypic variation in a fish predator affects multitrophic lake metacommunity structure

Contemporary insights from evolutionary ecology suggest that population divergence in ecologically important traits within predators can generate diversifying ecological selection on local community structure. Many studies acknowledging these effects of intraspecific variation assume that local populations are situated in communities that are unconnected to similar communities within a shared region. Recent work from metacommunity ecology suggests that species dispersal among communities can also influence species diversity and composition but can depend upon the relative importance of the local environment. Here, we study the relative effects of intraspecific phenotypic variation in a fish predator and spatial processes related to plankton species dispersal on multitrophic lake plankton metacommunity structure. Intraspecific diversification in foraging traits and residence time of the planktivorous fish alewife (Alosa pseudoharengus) among coastal lakes yields lake metacommunities supporting three lake types which differ in the phenotype and incidence of alewife: lakes with anadromous, landlocked, or no alewives. In coastal lakes, plankton community composition was attributed to dispersal versus local environmental predictors, including intraspecific variation in alewives. Local and beta diversity of zooplankton and phytoplankton was additionally measured in response to intraspecific variation in alewives. Zooplankton communities were structured by species sorting, with a strong influence of intraspecific variation in A. pseudoharengus. Intraspecific variation altered zooplankton species richness and beta diversity, where lake communities with landlocked alewives exhibited intermediate richness between lakes with anadromous alewives and without alewives, and greater community similarity. Phytoplankton diversity, in contrast, was highest in lakes with landlocked alewives. The results indicate that plankton dispersal in the region supplied a migrant pool that was strongly structured by intraspecific variation in alewives. This is one of the first studies to demonstrate that intraspecific phenotypic variation in a predator can maintain contrasting patterns of multitrophic diversity in metacommunities.     

Higher zooplankton species richness associated with an invertebrate top predator

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Geographical Distribution of Testate Amoebae in Tibet and Northwestern Yunnan and their Relationships with Climate

In Asia, especially in China, our knowledge of the distribution of testate amoebae is still limited. In this paper, the geographical distribution of testate amoebae in Tibetan Plateau and northwestern Yunnan Plateau, southwest China and their relationships with the climatic factors have been studied. We found testate amoebae shifted in the most dominant species and increased in species (or genus) richness from northwest to southeast. Further, the linear regression analyses revealed that both species richness and genus richness have higher positive correlations with the mean temperature of the warmest month and annual mean precipitation as contrasted with the mean altitude, which showed weak negative correlation. This indicates that the temperature and precipitation are more significant influences on the richness than the altitude. The cluster analysis based on the community structure, defined by Sørenson’s coefficient matrix, suggested four groups from the 10 physiographical regions. This geographical distribution pattern was also closely related with the climatic regionalization. The present climatic regionalization pattern of the study area originated from the uplift of Tibetan Plateau and mainly occurred in or after the late Pleistocene. Therefore, the geographical distribution of testate amoebae in our study area may have experienced complicated and drastic changes corresponding to the variation of the climate caused by the geological events.     

Landscape-scale Variation in Taxonomic Diversity in Four Groups of Aquatic Organisms: The Influence of Physical, Chemical, and Biological Properties

We evaluated several factors influencing the taxonomic richness of macrophytes, benthic invertebrates, snails, and fish in a series of northern Wisconsin lakes. We chose the study lakes to decouple the potential effects of ionic strength of lake water and stream connection, two factors that are usually highly correlated and therefore have been confounded in previous studies. In addition, our study lakes covered a wide range in a variety of characteristics, including residential development, abundance of exotic species, nutrient concentrations, predator abundance, and lake size. Species richness within each of the four taxonomic groups was significantly positively related to ionic strength (as measured by specific conductance); we also found secondary associations with other variables, depending on the specific group of organisms. The relationship between richness and lake area was dependent on the specific conductance of the lake and the vagility of the organisms; less vagile groups of organisms showed stronger and steeper species–area relationships in low-conductivity lakes. Further, after variance owing to specific conductance was removed, the presence of stream connections was positively related to species richness for fish, snails, and macrophytes as well as familial richness in benthic invertebrates. Our results indicate that lakes with relatively more groundwater input have lower extinction rates for all four groups of taxa and that lakes with stream inlets and outlets have enhanced immigration rates for fish, snails, benthic invertebrate families, and macrophytes. These findings link processes of immigration and extinction of four groups of organisms of varying vagility to landscape-level hydrologic characteristics related to the glacial history of the region.