Lake Assemblages Research Articles

Use of null models to explain crustacean zooplankton assemblages in waterbodies of Alerce Andino National Park (41°S, Chile)

The zooplankton assemblages in deep, mostly oligotrophic northern Patagonian lakes are characterized by low species numbers and a marked dominance of calanoid copepods. In the present study, data collected in field work on six water bodies located in Alerce Andino National Park (41°S) were analysed using the Jaccard Index of community similarity and a co-occurrence of null models, and such with the aim of determining potential regulating factors for the observed crustacean assemblages, using a presence-absence matrix. A significant correlation between species number and surface area was found. The null model used species co-occurrence, and the basis of this model is that the species associations observed are random. The results revealed the absence of regulating factors and indicate that the sites are relatively homogeneous, with low species numbers and similar plankton assemblages at all studied sites. This finding is in accordance with similar descriptions for zooplankton assemblages in other Chilean Patagonian lakes.

Discovering the Hidden Biodiversity of Crustacea (Branchiopoda, Maxillopoda and Ostracoda) Assemblages in the High Mountain Lakes of Kackar Mountains (Turkey)

Discovering the Hidden Biodiversity of Crustacea (Branchiopoda, Maxillopoda and Ostracoda) Assemblages in the High Mountain Lakes of Kackar Mountains (Turkey)

Discussion: a critique of Possible waterways between the Marmara Sea and the Black Sea in the late Quaternary: evidence from ostracod and foraminifer assemblages in lakes İznik and Sapanca, Turkey, Geo-Marine Letters, 2011

The identification of past connection routes between the Black Sea and the Sea of Marmara, other than the traditional one through to the Bosphorus Strait, would be of considerable interest to the international scientific community. Nazik et al. (Geo-Mar Lett 31:75–86 (2011) doi:10.1007/s00367-010-0216-9) suggest the possibility of two alternative waterway connections via lakes Sapanca and Iznik. Their Black Sea to Sea of Marmara multi-connection hypothesis, which is based on undated marine fossils collected in both lakes from surficial grab samples, conflicts with many earlier studies. In this contribution, the hypothesis and the underlying data are discussed in the light of previous tectonic, sedimentological and limnological findings showing that it is impossible to have had marine connections through lakes Sapanca and Iznik during the last 11.5 ka. Global sea-level trends and tectonic uplift rates would accommodate a connection between the Sea of Marmara and Lake Iznik in the middle Pleistocene. Uplift rates for the northern block of the North Anatolian Fault, when compared with the global sea-level curve, clearly indicate that there cannot have been a connection through the Izmit Gulf–Lake Sapanca–Sakarya Valley for at least the past 500 ka. Moreover, borehole sediments along the western shores of Lake Sapanca, which reach down to the bedrock, do not contain any marine fossils.

Seasonal and microhabitat influences on diatom assemblages and their representation in sediment traps and surface sediments from adjacent High Arctic lakes: Cape Bounty, Melville Island, Nunavut

The spatial (i.e. microhabitat) and temporal (i.e. seasonal) characteristics of diatom assemblages in adjacent High Arctic lakes were studied intensively June–August 2004. These baseline data are used to improve understanding of modern diatom community dynamics, as well to inform paleoenvironmental reconstructions. Diatoms were collected approximately weekly through the melt season from each principal benthic substrate (moss/macrophyte, rock scrapes, littoral sediment), plankton, and sediment traps, and were compared to the uppermost 0.5 cm of a surface core obtained from the deepest part of the lake where sediment cores are routinely collected. Water samples were collected concurrently with diatom samples to investigate species–environment relationships. The lakes share approximately half of their common taxa, the most abundant overall in both lakes being small Cyclotella species. Results of detrended correspondence analysis (DCA) indicate that the largest gradient in species turnover existed between benthic and planktonic communities in both lakes, and that sediment trap and the surface core top samples most closely resemble the planktonic assemblage, with an additional contribution from the lotic environment. Our results indicate clear micro-spatial controls on species assemblages and a degree of disconnection between the benthos and deep lake sediments that manifests as an under-representation of benthic taxa in deep lake surface sediments. These findings are particularly relevant in the context of interpreting the paleoenvironmental record and assessing ecosystem sensitivity to continued climate change.

Palaeoecological implication of ostracod and gastropod assemblages of the Holocene lake records from the Ganga Plain

Palaeoecological implication of ostracod and gastropod assemblages of the Holocene lake records from the Ganga Plain

Macrozoobenthic assemblages in relation to environments of the Yangtze-isolated lakes

Eutrophication can shift lakes from a clear, macrophyte-dominated state to a turbid, algae-dominated state, and different habitat condition supports different fauna. Macrozoobenthos are good indicators of water environment, and studies on macrozoobenthic assemblage characteristics can help us to know which state a lake is in, thus provide the basis for its eutrophication control. In this study, a systematic investigation on macrozoobenthos was conducted in 17 Yangtze-isolated lakes to explore the macroecological laws of macrozoobenthic assemblages. Detrended correspondence analysis (DCA) revealed that variance of benthic assemblage structure occurred in two types of lakes. In macrophytic lakes, altogether 51 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2231 individuals.m(-2) and 1.69 g dry weight.m(-2), respectively. Macrozoobenthic assemblage was characterized by dominance of scrapers (i.e. gastropods). In algal lakes, altogether 20 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2814 individuals.m(-2) and 1.38 g dry weight.m(-2), respectively. Macrozoobenthic assemblage was characterized by dominance of collector-gatherers (i.e. oligochaetes). Wet biomass of submersed macrophytes (B-Mac) and phytoplankton chlorophyll a concentration (Chl a) were demonstrated as the key factor structuring macrozoobenthic assemblages in macrophytic and algal lakes, respectively.

Macrophytes assemblages in mountain lakes of Huerquehue National Park (39ºS, Araucania Region, Chile)

The lakes studied (Tinquilco, Verde, Toro, Chico) are located in the Huerquehue National Park (39°08'S, 71°40'W), Chile. An inventory of the aquatic and riparian species was performed between December 2005 and March 2006. A null model analysis was done to determine the existence of regulatory factors of species associations, and the Jaccard index was applied to determine floristic similarities. Seventy- five species were identified. The greatest number (54) and highest percentage of introduced species (37%) occurred at Tinquilco Lake, placing it in the category of high human disturbance. Verde Lake, on the other hand, presented the lowest number of species (21), and the percentage of introduced species did not exceed 20% in the other three lakes, which are considered to have low human disturbance. The analysis of the null model revealed the presence of regulatory factors in one of the three simulations. However, in the other two simulations, the species associations appeared to be random, presumably because many species were repeated at the study sites. According to the Jaccard index, Tinquilco Lake is noticeably different from the other lakes, probably due to its transition from oligotrophy to mesotrophy.

The chironomid‐temperature relationship: expression in nature and palaeoenvironmental implications

Fossils of chironomid larvae (non-biting midges) preserved in lake sediments are well-established palaeotemperature indicators which, with the aid of numerical chironomid-based inference models (transfer functions), can provide quantitative estimates of past temperature change. This approach to temperature reconstruction relies on the strong relationship between air and lake surface water temperature and the distribution of individual chironomid taxa (species, species groups, genera) that has been observed in different climate regions (arctic, subarctic, temperate and tropical) in both the Northern and Southern hemisphere. A major complicating factor for the use of chironomids for palaeoclimate reconstruction which increases the uncertainty associated with chironomid-based temperature estimates is that the exact nature of the mechanism responsible for the strong relationship between temperature and chironomid assemblages in lakes remains uncertain. While a number of authors have provided state of the art overviews of fossil chironomid palaeoecology and the use of chironomids for temperature reconstruction, few have focused on examining the ecological basis for this approach. Here, we review the nature of the relationship between chironomids and temperature based on the available ecological evidence. After discussing many of the surveys describing the distribution of chironomid taxa in lake surface sediments in relation to temperature, we also examine evidence from laboratory and field studies exploring the effects of temperature on chironomid physiology, life cycles and behaviour. We show that, even though a direct influence of water temperature on chironomid development, growth and survival is well described, chironomid palaeoclimatology is presently faced with the paradoxical situation that the relationship between chironomid distribution and temperature seems strongest in relatively deep, thermally stratified lakes in temperate and subarctic regions in which the benthic chironomid fauna lives largely decoupled from the direct influence of air and surface water temperature. This finding suggests that indirect effects of temperature on physical and chemical characteristics of lakes play an important role in determining the distribution of lake-living chironomid larvae. However, we also demonstrate that no single indirect mechanism has been identified that can explain the strong relationship between chironomid distribution and temperature in all regions and datasets presently available. This observation contrasts with the previously published hypothesis that climatic effects on lake nutrient status and productivity may be largely responsible for the apparent correlation between chironomid assemblage distribution and temperature. We conclude our review by summarizing the implications of our findings for chironomid-based palaeoclimatology and by pointing towards further avenues of research necessary to improve our mechanistic understanding of the chironomid-temperature relationship.

Discrete thermal windows cause opposite response of sympatric cold-water fish species to annual temperature variability

Cold-water fish populations in lakes are predicted to be most vulnerable to global warming due to their geographical isolation and their requirement for habitats with low temperatures. In contrast, higher fisheries catches of cold-water species often correlate with warmer winter and spring temperatures. Mechanistic understanding of the relationships between annual temperatures and population densities can only be achieved by integrating physiology and behavioral ecology of the focal species, an approach that has so far not been applied to freshwater fish populations. We took advantage from a unique biological system, the coexistence of two cold-water Coregonus species in a deep lake. These fish species show discrete thermal windows (4–5°C vs. 7–9°C) and life histories (spring- vs. autumn-spawning). We analyzed short (6–11 years) time series of pelagic fish densities obtained by hydroacoustics and trawl catches, their zooplankton prey densities, and water temperature in Lake Stechlin (Germany). Young-of-year fish densities increased after warm winters. In contrast, densities of juveniles and adults were correlated with metalimnetic June temperatures, but an opposite response direction of the sympatric species was caused by their discrete thermal windows. Densities of the species with a 4–5°C thermal optimum increased in years with warm June, whereas densities of the other species with a 7–9°C optimum declined in these warm years. The occupied depths of both populations at night shifted towards less suitable water temperatures if densities of the competing species increased, suggesting interactive niche segregation. Therefore, growth of fishes may be reduced and hence mortality increased by additional metabolic costs induced by occurrence in layers outside of the metabolic optima. Temperature-driven inter- and intra-specific competition in the metalimnetic layer may cause a complex response of cold-water fish assemblages in lakes to warming. More approaches testing the relative performance of interacting species are needed to improve predictions on the consequences of global change on lake ecosystems.

Status of Fishes in Selected Adirondack Lakes: Eight Decades of Changing Assemblage Composition

Twenty-six taxa of fish were present in eighteen lakes in the southwestern quadrant of the Adirondack Park, Herkimer and Hamilton Counties, New York. Species richness in the lakes ranged from 1 to 18 species. Here we assess the condition and composition of the fish assemblages in lakes and compare in-lake changes in species composition over an 80-yr period. To examine assemblage condition we estimated population size of species in the lakes using mark-and-recapture techniques. To examine change in composition we compared the assemblage structure of these lakes to that present in two previous surveys. Populations of all but the rarest species comprised several size classes, indicating successful recruitment for all common species in all lakes. Most lakes support a rich, viable assemblage, although all but one includes, and many are dominated by, exotic species. Although the lakes studied are in one ecoregion and often in the same subdrainage, species composition differed among lakes and composition and abundance differed within lakes over time. Assessments of the fish assemblage composition in these lakes, when compared over time showed marked differences. These differences might be the result of several factors, but the presence of exotic taxa and extirpation of native fishes can explain gross changes in fish assemblage composition in these Adirondack lakes.

Seasonal variation and influence of turbidity and salinity on the zooplankton of a saline lake in central Argentina

The limnology of saline water bodies at other latitudes is fairly well known, but in Argentina such studies have only recently begun. The applicability of many conclusions regarding the functioning of these environments around the world is limited due to the scant ecological knowledge of some endemic species recorded in the assemblages of Argentine lakes. The aims of this work were to determine the effects of salinity and inorganic turbidity on the taxonomic composition, abundance, and zooplankton biomass in a shallow, hypereutrophic, mesosaline lake in the north of La Pampa province characterized by seasonality, variations in level and salinity, and the lack of macrophytes and fishes, and to compare it with other shallow lakes of the province. We found important differences with other saline lakes: the species richness was lower; the mean abundance of zooplankton was between four and six times higher; and rotifers, which were not affected by salinity or the concentration of inorganic suspended solids, were numerically predominant. Crustaceans, on the other hand, were negatively affected by these environmental factors. Biomass was two- fold higher than that recorded in the same period in two shallow lakes of Pampa, with similar nutrient concentrations but lower salinities.

Changes in phytoplankton, benthic invertebrate and fish assemblages of boreal lakes following invasion by Gonyostomum semen

Summary 1. During recent decades, Gonyostomum semen populations have spread in northern temperate regions forming dense blooms that may dominate the phytoplankton assemblage for extended periods. In this study, we investigate the effects of G. semen blooms in boreal brown water lakes with special emphasis on phytoplankton, fish and benthic invertebrate assemblages using data from 10 boreal lakes sampled annually over a 10-year period. 2. Significant differences in phytoplankton and benthic invertebrate assemblages were found between lakes with high (3.01 mm3 L−1; >80% phytoplankton biomass) and lakes with low G. semen biomass (0.03 mm3 L−1; <5% phytoplankton biomass). In particular, high G. semen lakes had lower biomass of smaller, edible phytoplankton and a higher abundance and biomass of benthic invertebrates, especially Chaoborus flavicans, and perch than low G. semen lakes. 3. The length distribution of fish also suggested a tendency towards large and older fish and a lower recruitment success in high G. semen lakes, as denoted by lower abundances of fish shorter than 10 cm and higher biomass and abundance of fish longer than 15 cm in high G. semen lakes. 4. This study shows that high G. semen lakes are characterised by less edible phytoplankton, dominance by a few species and enhanced benthic secondary and fish production. Hence, the conjecture that high biomasses of G. semen create a bottleneck in the energy transfer to higher trophic levels seems less likely in boreal lakes.

Nearshore fish assemblages associated with introduced predatory fishes in lakes

Changes to native fish assemblages in lakes are commonly associated with introduced predatory fishes. How fish assemblages change as multiple predatory species are introduced is not well understood. This study investigated the relationship between the presence of introduced large-bodied predatory fishes (largemouth bass Micropterus salmoides, pike Esox lucius, rock bass Ambloplites rupestris, smallmouth bass Micropterus dolomieu, walleye Sander vitreus) and the composition of native fish assemblages in littoral areas of 40 lakes in Algonquin Provincial Park, Ontario, Canada. Fish assemblages were compared across lakes of different predator composition, and within lakes before and after recent predator invasions. The presence of an introduced predator was associated with significantly different native fish assemblages across lakes, after controlling for environmental and spatial variables. Native fish assemblages did not significantly vary across lakes with more than one predator species. Furthermore, while declines in native species richness over time were observed in a number of lakes, these were not associated with introductions of additional predators. Several small-bodied species (brook stickleback Culea inconstans, fathead minnow Pimephales promelas, finescale dace Chrosomus neogaeus, and northern redbelly dace Chrosomus eos) consistently showed strong negative correlations with predator presence. The results suggest that predatory fish introductions alter native fish assemblages and that this impact is consistent regardless of the number of predatory species introduced. Copyright © 2011 John Wiley & Sons, Ltd and Her Majesty the Queen in Right of Canada.

Assessing lake typologies and indicator fish species for Italian natural lakes using past fish richness and assemblages

In order to establish a fish-based typology of Italian lakes and identify possible reference and indicator fish species for each lake type, we analysed historical data on fish assemblages of all Italian natural lakes >0.5 km2 from the period prior to the major decline in water quality in the 1950s. General linear regression models showed the ecoregion and lake altitude being the best predictors of fish species richness. The number of species was significantly higher in the Alpine than in the Mediterranean ecoregion. Among Alpine lakes, the number of fish species increased significantly with lake volume whilst decreased with altitude. In the Mediterranean lakes, none of the selected parameters was significant. Cluster analysis of fish assemblages (presence/absence) divided the lakes of the Alpine and Mediterranean ecoregions into four and two types, respectively. Pike (Esox lucius), rudd (Scardinius erythrophthalmus) and tench (Tinca tinca) were the main indicator species for the small and mostly shallow lakes in both the Alpine (Type 1) and Mediterranean (Type 6) ecoregions, minnow (Phoxinus phoxinus) for the alpine high altitude lakes (Type 2) and landlocked shad (Alosa fallax lacustris), European whitefish (Coregonus lavaretus) and burbot (Lota lota) for the large and very deep alpine lakes (Type 4). The European whitefish was the only indicator species for the deep Mediterranean lakes (Type 5). These species and associated fish assemblages may be useful indicators in future assessments of the ecological status of Italian lakes according to the European Directives (2000/60/EC and 2008/105/EC).

Spatial variation of modern pollen from surface lake sediments in Yunnan and southwestern Sichuan Province, China

To provide accurate analogues for fossil pollen records from lake cores, we analyzed surface sediments from 42 lakes of Yunnan and southwestern Sichuan Province, China (located between about 1500 and 4600 m elevation) for pollen and spores. The pollen analysis reveals that although large amounts of arboreal pollen, such as Pinus, Picea and Abies, Betula, Juglans, deciduous oaks, evergreen oaks, and Rosaceae, from lower elevations are introduced into sub-alpine and alpine lakes by upslope winds, the pollen assemblages of surface lake sediments among and within different vegetation types can still be distinguished by their pollen spectra and indicator species. For example, Alnus is an indicator of the pollen assemblages of lakes among the Pinus yunnanensis forest-Evergreen broadleaved forest or P. yunnanensis forest-Mixed Pinus and Quercus forest. Tsuga and Ericaceae are indicators of the pollen assemblages of lakes in the Picea and Abies forest or the Picea and Abies forest-Alpine ( Rhododendron) shrubland. Little pollen from Picea, Abies, Larix and Tsuga is transported downhill in lake sediments, indicating that lake cores near the lower limit of the Picea and Abies forest more correctly reflect climatic changes than lake cores near the tree line (namely the upper limit of the Picea and Abies forest) when using fossil pollen data. Principal component analysis basically separates surface lake samples below and above 3200 m a.s.l. However, it does not distinctly distinguish between samples from two different vegetation types above 3200 m a.s.l. because percentages of some dominant pollen types, such as Pinus, Picea and Abies, Betula, Juglans, deciduous oaks, evergreen oaks, and Rosaceae, do not markedly change with strong upslope transport.

Determining algal assemblages in oligotrophic lakes and streams: comparing information from newly developed pigment/chlorophyll a ratios with direct microscopy

Summary 1. Pigment analyses by high performance liquid chromatography (HPLC) are commonly used for determining algal groups in marine and estuarine areas but are underdeveloped in freshwaters. In this study, 15 characteristic pelagic algal species (representing five algal groups) of oligo- / mesotrophic lakes were cultured and pigment / Chl a ratios determined at three light intensities. 2. With the exception of cyanophytes, light treatment had little effect on pigment / Chl a ratios. This justifies the use of the same pigment / Chl a ratios during seasonal studies where light conditions may change. 3. The determined pigment / Chl a ratios were tested on seasonal samples from five oligo- / mesotrophic lakes and three streams using CHEMTAX software. Pigment ratios of both pelagic and benthic algal communities from the lakes and streams were analysed to determine whether the pelagic algae-based ratios can be used for benthic algal communities. 4. HPLC combined with CHEMTAX was useful for identifying freshwater phytoplankton classes and for quantifying the abundance of phytoplankton groups. However, although correlations were significant for six of seven phytoplankton classes studied, they were weak and varied with season. 5. HPLC was valid for quantifying benthic diatom groups in stream samples, whereas for lakes more benthic algal groups were recorded with HPLC than with microscopy and correlations between the two methods were not significant. 6. The use of both HPLC and microscopy is recommended as a cost-efficient method for analysing many samples. It is crucial, however, that the CHEMTAX software is calibrated with the correct information, and the user is aware of the limitations.

A Null Model to Study Community Structure of Microcrustacean Assemblages in Northern Chilean Shallow Lakes

The inland water bodies of northern Chile (18-27°S) are characterized by high salinity levels and impoverished species richness. This study presents field observations of species associations sampled from shallow water bodies in the Antofagasta region of northern Chile (23°S). A species presence-absence matrix was created for calculating the Jaccard Index of community similarity and for testing null models of species associations, with the aim of determining whether species associations are random or not. The results of the Jaccard Index calculations indicated the existence of defined groups, including three sites with Artemia franciscana, two sites with Boeckella poopoensis, and a sixth site only containing the ostracod Sarscypridopsis aculeata. The results of the null model analysis denoted the presence of regulating factors only in fixed-fixed simulation, that is the most robust in comparison to the other two simulations that denoted absence of regulator factors in species associations. The Jaccard indices and significant null model analysis agree with previous ecological descriptions of salinity as a determinant of species associations, whereas the non-significant results of the other two simulations could be due to the low number of species reported. The ecology and biogeography of these communities are also discussed.

Assessing the effects of multiple environmental stressors on zooplankton assemblages in Boreal Shield lakes since pre-industrial times

Zooplankton communities in Boreal Shield lakes of south-central Ontario, Canada, have become increasingly exposed to the effects of multiple anthropogenic stressors, such as declines in calcium (Ca) and total phosphorus (TP) concentrations, shifts in predation regimes, and climate warming. The paleolimnological approach provides an effective means of examining cladoceran zooplankton communities prior to the onset of these major environmental stressors and assessing how the increasing impacts of these stressors have affected zooplankton community composition. We examined the chitinized remains of cladocerans from recent and pre-industrial (pre- ~1850s) sediments in 42 oligotrophic lakes from south-central Ontario and compared these assemblages using ANOSIM and SIMPER. Differences in cladoceran assemblages since pre-industrial times were related to five environmental variables that significantly influence cladoceran community composition in surface sediments. These included measured physical (depth), chemical [Ca, pH, sulphate, dissolved organic carbon (DOC)], and biological (fish community biomass) limnological variables. Two changes were recorded in the cladoceran species assemblages of the study lakes. The first was a significant increase in the ratio of pelagic species compared to littoral species over time in most lakes which we cannot attribute to any measured environmental variable with certainty but it likely represents a multiple stressor effect. The second was changes in relative abundances of daphniid cladocerans in several lakes since pre-industrial times, which we attribute to the interactive effects of several environmental stressors, including: differences in Ca availability within our lakes, resulting in decreased abundances of daphniids over time in lakes with lower Ca levels; long-term increases in DOC concentrations, which may provide refuge for daphniids from visual predators; and long-term declines in TP concentrations which may contribute to the dominance of species that are more efficient grazers, such as daphniids. Overall, this study provides field-based evidence that the modern-day cladoceran communities in south-central Ontario lakes are different than they were prior to human settlement in the region, and therefore these paleolimnological data provide a long-term, historical component to contemporary cladoceran datasets and an extended perspective on how multiple environmental stressors have impacted aquatic organisms from Boreal Shield lakes.

Concordance among assemblages of upland Amazonian lakes and the structuring role of spatial and environmental factors

Conservation planning and biodiversity monitoring rely exclusively on the use of surrogate groups. However, the effectiveness of these groups in representing unknown biodiversity is rarely tested. These tests can be based on cross-taxon concordance (or congruence) analysis. In a second step, the main mechanisms underlying concordance can be investigated. Here, we evaluated the relative influence of local environmental factors and spatial processes on the patterns of beta-diversity exhibited by phytoplankton, zooplankton and benthic invertebrates and the strength of assemblage concordance among these assemblages in 38 upland Amazonian lakes (northern Brazil) over four years. Zooplankton and benthic invertebrates responded exclusively to environmental variables. These results are in accordance with the expected under the species sorting model, where local factors are the main mechanisms shaping assemblage structure. In general, patterns of concordance between the assemblages were weak and varied through time, indicating that the use of surrogates in freshwater ecosystems may be a flawed approach.

Use of Null Models to Explain Crustacean Zooplankton Assemblages in Northern Patagonian Lakes (Chile) with and Without Mixotrophic Ciliates

AbstractThe zooplankton assemblages in deep, mostly oligotrophic northern Patagonian lakes are characterized by a low species number and a marked dominance of calanoid copepods, as well as often by the presence of large mixotrophic ciliates (Stentor). In the present study, data collected in field work on four northern Patagonian lakes were analysed using co-occurrence of null models, with the aim to determine potential regulating factors for the observed crustacean and mixotrophic ciliate assemblages, using a presence-absence matrix. The null model uses species co-occurrence, and the basis of this model is that the species associations observed are random. The results revealed the absence of regulating factors and indicate that the sites are relatively homogeneous, with low species numbers, and similar plankton assemblages at all study sites. This finding coincides with similar descriptions for zooplankton assemblages in other Chilean Patagonian lakes.