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Understanding inter-annual variation in the density of young-of-the-year fish is an important tool for assessing stock status and guiding management decisions. We analyzed data spanning from 2003 to 2022 collected at Lipno Reservoir in Czechia. The study aimed to identify factors influencing the density of pikeperch (Sander lucioperca), a valuable predatory fish species in European waters. A bimodality test for the size class distribution has revealed the existence of two distinct YOY cohorts: extremely small (ES) and ordinary fingerlings. Using the Bayesian horseshoe prior method with 37 potential predictors, followed by linear regression, we observed that certain environmental factors similarly influenced both cohorts. Higher temperatures during spring and summer, coupled with increased densities of large and medium-sized cladocerans, positively affected the density of both cohorts. However, distinct influences were observed: for ordinary fingerlings, increased summer precipitation and a lower abundance of predators were beneficial, whereas, for ES fingerlings, summer copepod density emerged as an additional positive factor. This study emphasizes the importance of a detailed investigation of factors influencing pikeperch recruitment. Examining these drivers provides a clearer insight into the causes of variations in the early life stage, which is crucial for monitoring and managing populations in temperate reservoirs. [ABSTRACT FROM AUTHOR]

We analysed internal dispersal of zooplankton by waterbirds (endozoochory) in New Zealand, quantifying zooplankton eggs in faecal droppings collected at two lakes, Lake Rotoroa (Hamilton) and Lake Rotorua. Sixty-seven faecal droppings were collected from Mallard Ducks (20), Canada Geese (11), Greylag Geese (6), Black Swans (20) and Australian Coots (10). Fifty eggs were found, with a mean of 0.75 eggs per dropping, indicating that waterbirds consume zooplankton eggs, and that these pass through the digestive system. No significant difference was observed in the abundance of eggs among waterbird species, and no eggs hatched in the laboratory. Our results suggest that waterbird dispersal of zooplankton in New Zealand is occurring, but numbers being transported are low. Further, as non-native waterbirds such as mallard ducks and geese do not migrate in New Zealand to the extent they do elsewhere, they are likely not primary vectors for zooplankton dispersal. [ABSTRACT FROM AUTHOR]

Zooplankton provide critical food for threatened and endangered fish species in the San Francisco Estuary (estuary). Reduced food supply has been implicated in the Pelagic Organism Decline of the early 2000s, and further changes in zooplankton abundance, seasonality, and distribution may continue to threaten declining fishes. While we have a wealth of monitoring data, we know little about the abundance trends of many estuary zooplankton species. To fill these gaps, we reviewed past research and then examined trends in seasonality and abundance from 1972 to the present of three key but understudied zooplankton species (Bosmina longirostris, Acanthocyclops spp., and Acartiella sinensis) that play important roles in the estuary food web. We fit Bayesian generalized additive mixed models of each taxon’s relationship with salinity, seasonality, year, and geography on an integrated database of zooplankton monitoring in the upper estuary. We found marked changes in the seasonality and overall abundance of each study species. Bosmina longirostris no longer peaks in abundance in the fall months, Acanthocyclops spp. precipitously declined in all months and lost its strong relationship with salinity, and A. sinensis adult abundance has become more strongly related to salinity while juveniles have developed wider seasonal abundance peaks. Through these analyses, we have documented the relationship of each species with salinity and seasonality since the beginning of monitoring or their introduction, thus increasing our understanding of their ecology and importance in the estuary. These results can inform food-web models, be paired with fish data to model the contributions of these species toward fish abundance trends and be mirrored to elucidate other species’ trends in future studies.

This is the first study related to the zooplankton assemblage in the La García reservoir, an equatorial high Andean reservoir located in the central region of the department of Antioquia (Colombia). The main objective of the work was to know the composition and abundance of the zooplankton assemblage in the reservoir and to establish if there is any relationship between these and the physical and chemical variables measured. It was carried out during a monitoring program between the months of June and September 2014. Monthly samples were taken at three stations, from five depths throughout the water column, with a 10 L capacity sampling bottle. The collected material was filtered through a plankton net with a 30-mm of mesh size, identified and counted under an inverted microscope using a Sedgwick-Rafter counting cell. Depth and rainfall were the variables that exerted more influence on the zooplankton assemblages, reaching the highest density during the driest season, in the shallowest station and the least Secchi transparency. [ABSTRACT FROM AUTHOR]

Zooplankton are a pivotal component of the pelagic community, and their abundance and distribution are often strongly dependent on environmental conditions at sea. However, climate change can pose significant challenges to planktonic organisms. Therefore, in this study, we tried to address the possible effect of short-term climatic anomalies on the zooplankton community in the North Adriatic Sea, comparing mesozooplankton composition in June between two years with very different temperature and rainfall levels, i.e., 2019 and 2022. Environmental conditions at sea were significantly different, since 2022 faced rising temperatures in the northern part of the area and higher salinity and lower chlorophyll values in coastal samples. Our data unveiled a community shift, from a Noctiluca-dominated community to a crustacean-dominated one, and revealed that even offshore areas can be subject to changes, despite having quite stable environmental parameters. Our findings confirmed the influence of river inputs and temperature on the Adriatic community's distribution and composition, highlighting how climate-driven changes could have unpredictable effects on the whole Adriatic ecosystem. Indeed, each species has its own role in ecosystem functioning and climatic anomalies could uncouple the fine-scale connections that make up the pelagic trophic web. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate zooplankton species composition, abundance, and diversity in both natural and artificial lakes with varying trophic levels and to determine the relationship between zooplankton community structure and lake environmental conditions. This study hypothesized that correlations exist between zooplankton community structures and environmental parameters associated with eutrophication in natural and artificial lakes. Sampling was conducted across 16 distinct freshwater lentic ecosystems in Malaysia, including natural lakes/swamps, reservoirs, constructed lakes/ponds, and old mining lakes, spanning a range of trophic levels from mesotrophic to hypereutrophic conditions. Physicochemical parameters were measured in situ, while water and zooplankton samples were collected for nutrient analyses, as well as for zooplankton identification and enumeration. Throughout this study, a total of 58 zooplankton species, consisting of 36 species of rotifers, 12 species of cladocerans, and 10 species of copepods, were recorded. The highest zooplankton density (365.7 ± 13.7 ind L−1) was recorded in constructed lakes/ponds while the lowest density was recorded in natural shallow lakes/swamps (200.5 ± 25.5 ind L−1). On the other hand, significantly higher (p < 0.05) mean species diversity was observed in natural lakes/swamps (H’ = 2.2 ± 0.0); whereas, the lowest diversity was in old mining lakes (H’ = 1.5 ± 0.1). The canonical correspondence analysis (CCA) scores indicated that Polyarthra vulgaris and Chydorus ventricosus were the discriminating species in natural shallow lakes/swamps associated with high water transparency. Meanwhile, the small-sized cladocerans (Ceriodaphnia cornuta) and rotifers (Keratella spp., Brachionus spp., and Trichocerca spp.) were the most discriminating species in lakes with high turbidity, nutrients, and chlorophyll a concentrations, which are the main features of reservoirs and constructed lakes/ponds. Low density and diversity in old mining lakes were due to a low species number and the dominance of two species, Lophocharis curvata (38.8%) and Ptygura libera (39.7%). Overall, the high dominance of a specific zooplankton species resulted in lower biodiversity in artificial ecosystems compared to natural ecosystems. This study elucidated that zooplankton community structure in lakes was significantly influenced by the environmental conditions related to the lake trophic status.

A study was conducted to evaluate zooplankton species composition, abundance, and diversity in both natural and artificial lakes with varying trophic levels and to determine the relationship between zooplankton community structure and lake environmental conditions. This study hypothesized that correlations exist between zooplankton community structures and environmental parameters associated with eutrophication in natural and artificial lakes. Sampling was conducted across 16 distinct freshwater lentic ecosystems in Malaysia, including natural lakes/swamps, reservoirs, constructed lakes/ponds, and old mining lakes, spanning a range of trophic levels from mesotrophic to hypereutrophic conditions. Physicochemical parameters were measured in situ, while water and zooplankton samples were collected for nutrient analyses, as well as for zooplankton identification and enumeration. Throughout this study, a total of 58 zooplankton species, consisting of 36 species of rotifers, 12 species of cladocerans, and 10 species of copepods, were recorded. The highest zooplankton density (365.7 ± 13.7 ind L−1) was recorded in constructed lakes/ponds while the lowest density was recorded in natural shallow lakes/swamps (200.5 ± 25.5 ind L−1). On the other hand, significantly higher (p < 0.05) mean species diversity was observed in natural lakes/swamps (H' = 2.2 ± 0.0); whereas, the lowest diversity was in old mining lakes (H' = 1.5 ± 0.1). The canonical correspondence analysis (CCA) scores indicated that Polyarthra vulgaris and Chydorus ventricosus were the discriminating species in natural shallow lakes/swamps associated with high water transparency. Meanwhile, the small-sized cladocerans (Ceriodaphnia cornuta) and rotifers (Keratella spp., Brachionus spp., and Trichocerca spp.) were the most discriminating species in lakes with high turbidity, nutrients, and chlorophyll a concentrations, which are the main features of reservoirs and constructed lakes/ponds. Low density and diversity in old mining lakes were due to a low species number and the dominance of two species, Lophocharis curvata (38.8%) and Ptygura libera (39.7%). Overall, the high dominance of a specific zooplankton species resulted in lower biodiversity in artificial ecosystems compared to natural ecosystems. This study elucidated that zooplankton community structure in lakes was significantly influenced by the environmental conditions related to the lake trophic status. [ABSTRACT FROM AUTHOR]

The effects of climate-induced, long-term changes on mesozooplankton biomasses were studied based on monitoring data collected since 1966 in the northern Baltic Sea. We found that the biomasses of marine and brackish mesozooplankton had decreased significantly from 1966 to 2019, and a remarkable biomass and functional biodiversity loss took place in the mesozooplankton community. Our results put emphasis on the impact of two climate-driven regime shifts for the region's mesozooplankton community. The regime shifts took place in 1975 and 1976 and in 1989 and 1990, and they were the most important factor behind the abrupt biomass changes for marine mesozooplankton and total and marine Copepoda. Only the latter regime shift influenced the biomasses of brackish Copepoda, marine Cladocera, and total Rotifera. The decreasing length of the ice-cover period drove the decrease of the biomass of limnic Limnocalanus macrurus (Copepoda), while the winter North Atlantic Oscillation was behind biomass changes in the total and the brackish Cladocera. These findings may have important implications for planktivorous fish, such as Baltic herring, particularly in terms of their impact on commercial fishing.

Decadal trends in the zooplankton community were seasonally investigated in multiple monitoring transects of the western Mediterranean Sea during a period of increasing and record-high water temperatures. The transition area around the Baleares archipelago can be separated into two regions: the Alborán Sea and the Balearic Sea. Differences were found in the abundance and structure of the dominant zooplankton groups: the cladocerans and copepods. The highest zooplankton abundances were found during the stratified summer season, when cladoceran numbers peaked. However, copepods were more abundant during the winter. A marked seasonality was found in all groups and the dominant taxa: 114 species of copepods and 5 species of cladocerans were identified, but less than 8 species of copepods and 2 species of cladocerans dominated the populations. During the 2007–2017 study, warm and salty waters were observed in the Balearic Sea. In the Alborán Sea, cool and fresh waters were observed, along with a decline in chlorophyll. Irregular group and species trends were observed in both regions, exhibiting both increases and decreases depending on region and season. Trends differed, often oppositely, for the Alborán versus the Balearic Sea, with the transition region between them mirroring one or the other, switching with the seasons. The most dominant species, including Penilia avirostris and Clausocalanus arcuicornis, but also Evadne spinifera, C. lividus, C. furcatus, Paracalanus parvus, Acartia clausi, Centropages typicus, Subeucalanus monachus, and Calanus helgolandicus, are proposed as biological tracers to be used in further studies on climate and zooplankton community changes in the western Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Arctic landscapes are characterised by their numerous ponds and lakes. With increased climate warming and consequent changes in hydrological connectivity, the ecology of many of these waterbodies is expected to change.We sampled 13 ponds and 22 lakes for zooplankton and various limnological and physical environmental variables in the vicinity of Cambridge Bay, Nunavut (69.1169° N, 105.0597° W), with the aim of testing how well the degree of hydrological connectivity explained patterns in species composition and abundance and contributed to crustacean production. Ponds were hydrologically isolated while the lakes were arranged in four lake chains and ranged from the headwaters to highly inter‐connected lakes receiving water from one to 768 upstream lakes.In all sites combined, 77 zooplankton species were found, including 56 rotifers, six copepods, 11 cladocerans, two fairy shrimp species, a mysid, and a tadpole shrimp. We show that the zooplankton communities differed between hydrologically isolated (ponds) and connected (lakes) systems, with 17 species unique to ponds and 20 to lakes. Furthermore, the communities were more similar within lake chains and hence in lakes closer to each other. In ponds, distances between waterbodies had no impact on community similarity.Zooplankton abundance was higher in lakes (255 ind/L) than in ponds (65 ind/L) due to the higher number of rotifers that accounted for nearly 80% of the zooplankton abundance in lakes. In ponds, rotifers, cladocerans, and copepods were equally abundant. In terms of biomass, cladocerans represented 65% of total biomass in all waterbodies except for a chain of deep lakes that had abundant fish communities. In these lakes, cladoceran abundance and biomass were low and probably limited by fish predation.Zooplankton production was higher in ponds (4.6 mgC m−3 day−1) than in lakes (1.7 mgC m−3 day−1), and within lakes was lowest in the chain composed of large lakes (1.3 mgC m−3 day−1). The high production in ponds was closely linked to high zooplankton biomass and further explained by high gross primary production supported by relatively high nutrient concentrations in these shallow systems.Our study emphasises that hydrological connectivity is key to shaping zooplankton communities, although fish presence also appears to affect them. It shows that isolated ponds (that currently account for c83% of all waterbodies on southern Victoria Island) are hotspots of aquatic biological productivity that probably play an essential role in Arctic freshwater landscapes. Finally, our study provides critical baseline information on the current composition of Arctic zooplankton communities important for estimating climate change impacts. [ABSTRACT FROM AUTHOR]

Zooplankton in the Barents Sea have been monitored annually with a standard procedure with determination of size-fractioned biomass since the mid-1980s. Biomass of copepods and cladocerans was estimated based on measured abundance and individual weights taken from literature. Calanus species were dominant, making up ~85% of the estimated biomass of copepods. The second most important taxon was Oithona spp. (~0.5 g dry weight (dw) m−2, ~10%), followed by Metridia spp. (~0.15 g dw m−2, 2–3%) and Pseudocalanus spp. (0.10–0.15 g dw m−2, 1–5%). Estimated biomass of cladoceran taxa (Evadne and Podon) was low (0.01 g dw m−2). Calanus spp. contributed most of the biomass of the medium size fraction (1–2 mm), whereas small copepod species (Oithona , Pseudocalanus and others) contributed to the small size fraction (<1 mm). Estimated biomass of Calanus spp. and of the sum of small copepod species were both positively correlated with measured total zooplankton biomass (R 2 = 0.72 and 0.34, respectively). The biomass ratio of small copepod species to Calanus was similar in Atlantic and Arctic water masses (~0.15–0.2) but tended to increase with decreasing total biomass. This suggests a shift to relatively larger roles of small copepods as Calanus and total biomass decrease. [ABSTRACT FROM AUTHOR]

Acidification has harmed freshwater ecosystems in Northern Europe since the early 1900s. Stricter regulations aimed at decreasing acidic emissions have improved surface‐water chemistry since the late 1980s but the recovery of biotic communities has not been consistent. Generally, the recovery of flora and fauna has been documented only for a few lakes or regions and large‐scale assessments of long‐term dynamics of biotic communities due to improved water quality are still lacking. This study investigates a large biomonitoring dataset of pelagic and littoral crustacean zooplankton (Cladocera and Copepoda) from 142 acid‐sensitive lakes in Norway spanning 24 years (1997–2020). The aims were to assess the changes in zooplankton communities through time, compare patterns of changes across lake types (defined based on calcium and humic content), and identify correlations between abiotic and biological variables. Our results indicate chemical and biological recovery after acidification, as shown by a general increase in pH, acid neutralizing capacity, changes in community composition and increases in the total number of species, number of acid‐sensitive species and functional richness through time. However, the zooplankton responses differ across lake types. This indicates that the concentration of calcium (or alkalinity) and total organic carbon (or humic substances) are important factors for the recovery. Therefore, assessment methods and management tools should be adapted to the diverse lake types. Long‐term monitoring of freshwater ecosystems is needed to fully comprehend the recovery dynamics of biotic communities from acidification. [ABSTRACT FROM AUTHOR]

The development of a feeding protocol of copepods and cladocerans is of paramount significance nowadays because they are considered nutritionally enriched live feeds for rearing numerous aquaculture species. Two experiments were conducted to evaluate the suitability of the green microalga Monoraphidium littorale on the population density and egg production of copepods (Diaptomus sp., Cyclops sp.) and cladocerans (Moina sp., Diaphanosoma sp.). In the first experiment, three diets including live M. littorale (T1), baker’s yeast (T2), and a combination of live M. littorale and baker’s yeast (T3) were fed to copepods and cladocerans for 10 days to determine the best feed. The results indicated that T1 was the best diet for the population density and egg production of Diaptomus sp. whereas T3 was best for Moina sp., Diaphanosoma sp., and Cyclops sp. In the second experiment, three concentrations of M. littorale including 1 × 105 cells mL−1 (T1), 5 × 105 cells mL−1 (T2), 10 × 105 cells mL−1 (T3), and dried powder of M. littorale (T4) were fed for 10 days to the copepods and cladocerans. T3 was found as the best diet for Diaptomus sp. where the mean maximum population density and egg production was significantly higher (P ˂ 0.05). Moina sp. exhibited the best growth and egg production both in T2 and T3; and Diaphanosoma sp. exhibited the best growth both in T2 and T4 but egg production in T2, T3 and T4. Interestingly, in case of Cyclops sp. the mean maximum population density and egg production were significantly higher (P ˂ 0.05) in T4 where powdered green microalgae M. littorale were used as feed. Based on the findings of the present research, M. littorale both in live and dried powdered form may be used as a suitable feed for the culture of copepods and cladocerans.

The Niger River and its main tributaries (Sirba, Tapoa and Mékrou) in Niger were sampled during high and low water flow with the objectives of (1) comparing the taxonomic structure, diversity and abundance of the zooplankton community (rotifers, copepods, crustaceans) along the river and (2) determining which environmental or biological factors influence the distribution of the zooplankton communities most strongly. The impact of the tributaries at high-flow was also evaluated. Rotifers (32 taxa) were the most abundant and diverse followed by Cladocerans (13 taxa) and Copepods (three taxa). The mean number of taxa (16.5 and 17.6, respectively), the Shannon-Weaver diversity index (2.7 and 2.8, respectively) and the evenness (0.7 and 0.7, respectively) did not vary significantly between the high- or low-flow periods, or along the length of the Niger River and its tributaries. The mean zooplankton abundance was highest during low-flow periods (40 × 103 ± 45 × 103 ind. m−3) but showed no specific spatial pattern. During high-flow sampling, the mean zooplankton abundance (3 × 103 ± 2 × 103 ind. m–3) increased progressively downstream. RDA analysis showed that rotifers are associated with high conductivity and NO2− concentrations, copepods with chlorophyll a, while cladocerans were abundant when conductivity, chlorophyll a and NO2− concentrations were low. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms have been recognized as a problem in fresh water for about 150 years. Over the past 50 years, experimental studies on the subject have gained importance considering the increasing need to control toxic cyanobacterial blooms. This article presents information on the different lines of research that have been undertaken on zooplankton–cyanobacteria interactions over the past 50 years. These include information on filtering/ingestion rates and phytoplankton preferences of small and large rotifers, cladocerans, and copepods; growth rates of zooplankton on cyanobacterial diets; feeding rates of other freshwater invertebrates on cyanobacteria; role of zooplankton in top-down biomanipulation efforts; effect of cyanotoxins on zooplankton; bioaccumulation of cyanotoxins; and physical and chemical control of cyanobacterial blooms. We also highlight measures that have led to successful lake management and improvement of water quality in selected waterbodies. [ABSTRACT FROM AUTHOR]

The artificial propagation of commercially important fish species in Ethiopia is constrained by high mortality rate at the early stage of larval rearing and a subsequent poor growth performance during later stages. This is mainly due to absence of live feeds suited to the requirements of the larvae of the species. Although not organized, several studies have indicated that microalgae, copepods, cladocerans and rotifers are the dominant inhabitants in several water bodies that are the precursors in the larviculture of commercially important finfishes in the world. However, apart from studying the abundance and diversity of these important planktonic organisms, efforts made to culture any of them for use in the larviculture of commercially important fish species in Ethiopia is minimal. This may be due to the lack of comprehensive and organized information on the distribution and abundance of these important species in the context of their potential in aquaculture of live feeds in Ethiopia. The objective of this review is therefore to compile the available information on the abundance and distribution of the major potential live feed organisms in the Ethiopian water bodies with a special emphasis on freshwater live feed organisms currently used in larviculture of commercially important freshwater finfishes. In line with this, four potential live feeds (i.e. microalgae, rotifers, copepods and cladocerans) were included in the review. It is hoped that the review will provide baseline information for future research in the culture of economically important larval live feeds. [ABSTRACT FROM AUTHOR]

The Patagonian region, from the Andes to the steppe, includes a profuse hydrographic network with deep and shallow lakes. Here, we analyze the stoichiometric constraints for the large predaceous copepod Parabroteas sarsi in fish and fishless lakes. For this purpose, we examined previous literature data on the composition of the zooplankton community in different Patagonian lakes with and without fish (mainly introduced in the XX century) and own laboratory and field experiments. The ecological stoichiometry theory predicts that consumers need to attain specific elemental ratios to achieve maximum growth, and the geometric framework of nutrition proposes that consumers may need to combine food items to fulfill nutrient requirements. We show that the predaceous copepod does not necessarily encounter prey that fulfills their stoichiometric requirements, thus growth is impaired. However, through the combination of different prey, this predator can fulfill its requirements. In the presence of fishes, food webs change towards smaller-sized zooplankton species with the loss of low C:nutrient ratio species. In this sense, we demonstrate the direct and indirect impact of fish introduction on the stoichiometric balances and the disappearance of this invertebrate predator in lacustrine food webs. [ABSTRACT FROM AUTHOR]

Zooplankton plays an important role in aquatic food webs and changes in its abundance and diversity under changing climatic conditions can significantly affect the abundance and diversity of other aquatic organisms. The aim of the study was to assess quantitative and qualitative parameters of zooplankton development, dynamics of development of its dominant groups and the effect of water temperature. Species composition and abundance of zooplankton of the Kremenchuk Reservoir were studied in 2006, 2010–2012 and 2020 in relation to water temperature and pollution. Zooplankton species diversity fluctuated significantly over the years of the study. A total of 46 taxa were recorded in the reservoir during the study period. The number of recorded zooplankton taxa ranged 26 to 32 depending on the year. The most abundant zooplankters were Chydorus sphaericus, Copepoda nauplii, Brachionus diversicornis. The abundance of zooplankters in the reservoir during the study period ranged 23·103 to 256·103 ind./m3, and biomass 0.14 to 0.89 g/m3. A significant positive relationship was observed between the abundance of cladocerans, including some individual species (Ch. sphaericus and Ceriodaphnia sp.), and water temperature. Indicator species of water pollution in different years and in different parts of the Kremenchuk Reservoir differed significantly, which probably depended on the presence or absence (in a certain period of time) of polluting discharges. The total saprobity index in different years in different parts of the reservoir was in the range of 1.5–1.9. Structural indicators of zooplankton and its dominant complexes characterize the water in the Kremenchuk Reservoir as β-mesosaprobic. It is probably too early to assess the impact of climate change zooplankton as these changes are still unstable and short in time, but it is necessary to constantly monitor the biota of aquatic ecosystems to further study and summarize the data, which could later allow an identification of such changes.

The Patagonian region, from the Andes to the steppe, includes a profuse hydrographic network with deep and shallow lakes. Here, we analyze the stoichiometric constraints for the large predaceous copepod Parabroteas sarsi in fish and fishless lakes. For this purpose, we examined previous literature data on the composition of the zooplankton community in different Patagonian lakes with and without fish (mainly introduced in the XX century) and own laboratory and field experiments. The ecological stoichiometry theory predicts that consumers need to attain specific elemental ratios to achieve maximum growth, and the geometric framework of nutrition proposes that consumers may need to combine food items to fulfill nutrient requirements. We show that the predaceous copepod does not necessarily encounter prey that fulfills their stoichiometric requirements, thus growth is impaired. However, through the combination of different prey, this predator can fulfill its requirements. In the presence of fishes, food webs change towards smaller-sized zooplankton species with the loss of low C:nutrient ratio species. In this sense, we demonstrate the direct and indirect impact of fish introduction on the stoichiometric balances and the disappearance of this invertebrate predator in lacustrine food webs.

Broad‐scale assessment of biodiversity is needed for detection of future changes across substantial regions of the Arctic. Presently, there are large data and information gaps in species composition and richness of the freshwater planktonic and meiobenthos communities of the Russian Arctic. Analysis of these data is very important for identifying the spatial distribution and temporal changes in species richness and diversity of rotifers, cladocerans, and copepods in the continental Russian Arctic.We investigated biogeographic patterns of freshwater plankton and meiobenthos from c. 67° to 73°N by analysing data over the period 1960–2017. These data include information on the composition of rotifers, cladocerans, and copepods obtained from planktonic and meiobenthic samples, as well as from subfossil remains in bottom sediments of seven regions from the Kola Peninsula in the west, to the Indigirka River Basin (east Siberia) in the east.Total richness included 175 species comprised of 49 rotifer genera, 81 species from 40 cladoceran genera, and 101 species from 42 genera of calanoid, cyclopoid, and harpacticoid copepods. Longitudinal trends in rotifer and micro‐crustacean diversity were revealed by change in species composition from Europe to eastern Siberia. The most common and widespread species were 19 ubiquitous taxa that included Kellicottia longispina (Rotifera), Chydorus sphaericus s. lat. (Cladocera), Heterocope borealis, Acanthocyclops vernalis, and Moraria duthiei (Copepoda). The highest number of rare species was recorded in the well‐studied region of the Bolshezemelskaya tundra and in the Putorana Plateau.The total number of copepod and rotifer species in both Arctic lakes and ponds tended to increase with latitude. Relative species richness of copepods was positively associated with waterbody area, elevation, and precipitation, while relative species richness of cladocerans was positively related to temperature. This result is consistent with known thermophilic characteristics of cladocerans and the cold tolerance properties of copepods, with the former being dominant in shallow, warmer waterbodies of some western regions, and the latter being dominant in large cold lakes and waterbodies of eastern regions. Rotifers showed a negative association with these factors.Alpha‐ and β‐diversity of zooplankton in the Russian Arctic were strongly related to waterbody type. Lake zooplankton communities were more diverse than those in pond and pool systems. Moreover, the highest β‐diversity values were observed in regions that showed a greater breadth in latitude and highly heterogeneous environmental conditions and waterbody types (Bolshezemelskaya tundra and Putorana Plateau).Redistribution of freshwater micro‐fauna caused by human activities occurred in the 1990s and 2000s. As a result of climate warming, a few cladoceran species appear to have extended their range northward. Nevertheless, the rotifer and micro‐crustacean fauna composition and diversity of the majority of Arctic regions generally remain temporally conservative, and spatial differences in composition and species richness are chiefly associated with the differences between the warmer European and colder east Siberian climates. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms have been recognized as a problem in fresh water for about 150 years. Over the past 50 years, experimental studies on the subject have gained importance considering the increasing need to control toxic cyanobacterial blooms. This article presents information on the different lines of research that have been undertaken on zooplankton–cyanobacteria interactions over the past 50 years. These include information on filtering/ingestion rates and phytoplankton preferences of small and large rotifers, cladocerans, and copepods; growth rates of zooplankton on cyanobacterial diets; feeding rates of other freshwater invertebrates on cyanobacteria; role of zooplankton in top-down biomanipulation efforts; effect of cyanotoxins on zooplankton; bioaccumulation of cyanotoxins; and physical and chemical control of cyanobacterial blooms. We also highlight measures that have led to successful lake management and improvement of water quality in selected waterbodies.

In 2018, the faunas of Cladocera and Copepoda of four mountain Sphagnum peatlands in the Republic of North Ossetia and five in the Republic of Kabardino-Balkaria, Caucasus, Russia, were studied. For each area, species complexes peculiar both to the central part of the secondary water body and to the surrounding Sphagnum floating mat, at the edge of the water, were described. Altogether, 31 species of microcrustaceans were found in the material collected. Among them, two species of Cladocera and eight species of Copepoda were recorded from mountain water bodies of the North Caucasus for the first time. Montane Sphagnum peatlands were shown to be an outpost of northern species distributions, as confirmed by finding two Copepoda species typical of more northerly regions. The abundance of microcrustaceans in floating Sphagnum mats was often tens of times higher than in the water column. The habitat type, seasonality, latitude, longitude, altitude, temperature, acidity, and mineralization combined were shown to explain only 32.3% of variations in the species complexes. This indicates a complex factor regulation of the community structure in high-altitude conditions. [ABSTRACT FROM AUTHOR]

This study focuses on changes in zooplankton composition and abundance in Lake Nasser during different flood periods before the construction of the Grand Ethiopian Renaissance Dam (GERD). Field surveys were carried out in August 2016 (flood period), December 2016 (post-flood period), and May 2017 (pre-flood period). Fifteen sampling sites representing five sectors were selected to cover the lake whole area. The results revealed a highly significant difference (p ≤ 0.016) in the density of all identified zooplankton groups among different flood seasons and lake locations. The zooplankton standing crop during the flood was higher, by a factor of approximately 3.7, than that recorded in post-flood and pre-flood periods. Zooplankton was dominated by medium-sized Copepoda, two cyclopoids (Thermocyclops neglectus and Mesocyclops ogunnus) and one calanoid (Thermodiaptomus galebi). The euplanktonic rotifer Keratella cochlearis dominated, during post-flood and pre-flood periods, constituting approximately 83% and 77% of total rotifer densities, respectively. Keratella tropica occurred in greatest density during flood made up 52.6% of total rotifers. Diaphanosoma mongolianum was the main cladoceran during flood and post-flood periods, whereas Ceriodaphnia dubia densities were highest for pre-flood periods. This study found that flood regime affect zooplankton composition and density in Lake Nasser. [ABSTRACT FROM AUTHOR]

We investigated changes in the species richness, abundance, and composition of the zooplankton community in response to the formation of a small reservoir in the Caveiras River, southern Brazil. Zooplankton were collected using a motor-pump and a plankton net (68 μm mesh), with 600 L of water filtered per sample. Sampling occurred during the pre- (April, August, and December 2011) and post-impoundment (July and October 2013, and January 2014) phases of the Caveiras River. We identified 86 taxa in this study, and rotifers were the predominant group. The species richness and abundance of the zooplankton increased after the filling of the reservoir. Furthermore, the zooplankton community showed a clear change in the species composition between the phases before and after the formation of the reservoir, with the emergence of typical planktonic species. Changes in the structure of the zooplankton community were related to changes in limnological characteristics due to the impoundment of the river, mainly in the availability of food and in the concentration of nutrients.

Greece is situated in the East Mediterranean region and in the Balkan peninsula, i.e., a European biodiversity hotspot with high endemism in subterranean and freshwater fauna, highlighting the need to understand its biodiversity. A literature search was undertaken to present a checklist of cladocerans and copepods based on a compilation of published and current data, from 1892 up to 2022 from inland surfaces and subterranean water bodies from different regions of Greece. For Cladocera, 80 species were recorded (9 families with 35 genera). The most diverse families were Chydoridae (20 genera with 33 species) and Daphniidae (5 genera with 27 species). For copepoda, 134 taxa were recorded, in surface water bodies (12 families with 34 genera), subterranean water bodies (7 families with 27 genera), and parasitic copepods (3 families with 3 genera). The most diverse families in surface waters were Cyclopidae (15 genera with 41 taxa) and Diaptomidae (5 genera with 17 species), while those in subterranean waters were Cyclopidae (11 genera with 35 taxa) and Canthocamptidae (6 genera with 17 taxa). More species are expected to be discovered after sampling understudied regions, especially islands, as well as water bodies such as temporary pools, swamps, ditches, puddles, and the littoral parts of lakes, while molecular studies are needed to clarify various cases of complex taxonomy.

We present the presence/absence species list (Table 1) of rotifer, cladoceran, and copepod (Calanoida, Harpacticoida, and Cyclopoida) fauna from seven Arctic regions of Russia (the Kola Peninsula, the Pechora River Delta, the Bolshezemelskaya tundra, the Polar Ural, the Putorana Plateau, the Lena River Delta, and the Indigirka River Basin) based on our own and literature data. Our own records were obtained by analyzing samples of zooplankton, meiobenthos, and two cores of bottom sediments (from the Kola Peninsula and the Bolshezemelskaya tundra lakes) that we collected once in July or August in 1992, 1995–2017. To supplement the list, we used relevant literature with periods of research from the 1960s to the 2010s. The list is almost identical to “Dataset 2: Zooplankton and Meiofauna across Arctic Regions of Russia”, which was analyzed but not published in [1]. The detailed analysis of this list revealed the specific composition of the aquatic fauna associated with the climatic and geographical factors [1]. The data provide information on the current state of biodiversity and species richness in Arctic fresh waters and can serve as the basis for monitoring these environments and predicting how they are likely to change in the future.

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We investigated changes in the species richness, abundance, and composition of the zooplankton community in response to the formation of a small reservoir in the Caveiras River, southern Brazil. Zooplankton were collected using a motor-pump and a plankton net (68 μm mesh), with 600 L of water filtered per sample. Sampling occurred during the pre- (April, August, and December 2011) and postimpoundment (July and October 2013, and January 2014) phases of the Caveiras River. We identified 86 taxa in this study, and rotifers were the predominant group. The species richness and abundance of the zooplankton increased after the filling of the reservoir. Furthermore, the zooplankton community showed a clear change in the species composition between the phases before and after the formation of the reservoir, with the emergence of typical planktonic species. Changes in the structure of the zooplankton community were related to changes in limnological characteristics due to the impoundment of the river, mainly in the availability of food and in the concentration of nutrients. [ABSTRACT FROM AUTHOR]

Background In reservoirs, zooplankton strongly interact with the physical and chemical characteristics of water, and this interaction is mainly influenced by climate variation and the different methods used to manage the dam water level. Therefore, the aim of this study was to evaluate how the distinct operating modes of two cascade reservoirs affected the richness, abundance, and composition of zooplankton, both spatially (intra and inter-reservoirs) and temporally (annual and seasonal). In this study, the upstream reservoir (Salto Santiago) operates using the storage method, with a water retention time (WRT) of 51 days, whereas the downstream reservoir (Salto Osório) operates using the run-of-river method, with a WRT of 16 days. Methods Zooplankton samples were collected for 16 consecutive years from the two reservoirs located on the Iguaçu River, Brazil. A total of 720 samples were collected. Four-way ANOVAs were used to determine the differences in richness and abundance of the zooplankton among years, periods, reservoirs, and environments. Multidimensional non-metric scaling (NMDS) and an analysis of similarities (ANOSIM) were used to describe similarity patterns in species composition. Finally, a canonical correspondence analysis (CCA) was used to select the environmental predictors that best explained the variation in zooplankton abundance data. Results We identified a total of 115 taxa in this study, and rotifers were the richest group. In contrast, the copepods were the most abundant. The four-way ANOVA results showed significant differences in the species richness and abundance of the zooplankton among years, periods, reservoirs, and environments. The NMDS ordination and ANOSIM test indicated that the largest differences in zooplankton species composition were annual and seasonal differences. Finally, the CCA showed that these differences were mainly associated with changes in water transparency, temperature, and the chlorophyll a, phosphorus, and total dissolved solids concentrations. Discussion Inter-annual changes in zooplankton species composition showed that over time, large filters-feeders (e.g., large daphinids and calanoid copepods) were replaced by small cladocerans (e.g., bosminids) and generalist rotifers. The highest species richness was associated with the fluvial environment, whereas the highest abundance was associated with the transitional and lacustrine reservoir environments. Variations in water temperature, nutrients, and food availability explained the annual and seasonal changes in community structure, whereas variations in the water flow characteristics of the environments explained the longitudinal changes in the richness and abundance of zooplankton in reservoirs. The differences in zooplankton structure between the two reservoirs can be explained by the functional differences between the two systems, such as their WRTs and morphometrics.

In Mediterranean temporary ponds, the timing of annual flooding is highly variable and depends on heavy seasonal rains. Ponds can flood in the autumn, winter, or spring, and thus the environmental conditions faced by emerging zooplankton can be very different. We performed an experiment in a climatic chamber where we simulated annual variation in natural temperature and light conditions to study how differences in pond-filling season affected zooplankton assemblage composition. We sampled sediments from a temporary pond and placed them in aquariums that were filled with water during three different seasons: autumn (October), winter (January), and spring (March). Zooplankton abundance, species richness, diversity, and assemblage composition differed significantly among treatments, and post-inundation temperature and pH appeared to be the main drivers of these differences. Diversity was highest in the winter treatment. It was lower in the autumn treatment and the spring treatment, and no indicator species were present in the latter. Our results suggest that interannual variability in initial inundation conditions favours the emergence of different species and thus contributes to high species richness in the egg bank. However, climate change and/or groundwater drawdown could delay pond flooding, impoverishing the zooplankton assemblage in the long term. [ABSTRACT FROM AUTHOR]

Despite the rapidly changing winter conditions in temperate ecosystems, little attention has been devoted to the effects of these changes on lake ecology. Few studies on the seasonal changes in abundance and biomass of the major groups of the metazooplankton community (i.e. rotifers, cladocerans and copepods) in northern oligotrophic lakes include data from the ice-covered winter months. This study reports monthly variation in zooplankton abundance and biomass from June 2010 to October 2011, including winter, in an oligotrophic, subalpine lake in southeastern Norway (Lake Atnsjøen). Changes in rotifer, cladoceran, copepod, and total zooplankton abundances and biomass were related to seasonal variation in water temperature and phytoplankton biomass by means of ordination analysis. The zooplankton abundance and biomass were much lower in winter than during the open water season. However, an under-ice phytoplankton bloom occurred during the final winter months, when snow cover and ice thickness were reduced and (presumably) light penetration increased, leading to an increase in abundance of copepod nauplii. Winter zooplankton abundance was dominated by copepods and rotifers, while winter zooplankton biomass was dominated by copepods and cladocerans. Both phytoplankton and zooplankton had two biomass peaks in 2010 and one peak in 2011. Rotifers dominated zooplankton abundance with a peak in August and total zooplankton abundance followed a similar pattern. In contrast, cladocerans dominated zooplankton biomass with a peak in July and total zooplankton biomass also peaked at this time. Rotifer and total zooplankton abundance and rotifer biomass were most closely correlated to water temperature. However, cladoceran biomass and total biomass were most closely correlated with phytoplankton biomass, but also appeared to be dependent on other carbon sources. Estimates of non-phytoplankton particulate organic carbon indicated that this part of the carbon pool could be an additional food source for zooplankton particularly in early and mid-winter. The longer growing season in 2011 than in 2010, owing to earlier ice-off in 2011, may have contributed to higher phytoplankton and zooplankton biomass in 2011. With climate warming, this is an expected change in temperate lake ecosystems.

Turbidity influences the success of fish feeding, but little is known about the difference in the effects of turbidity as a result of organic and inorganic matter. To assess the feeding behaviour of a native fish, Goodea atripinnis, under turbid conditions (up to 120 NTU) generated by Microcystis aeruginosa or silt, we conducted mesocosm experiments for 25 days using 40-L plastic mesocosms. Each tank received two G. atripinnis individuals (predators) with a mean total length 61 mm and cladoceran zooplankton (prey) (Alona glabra, Chydorus sphaericus, Moina macrocopa, Simocephalus vetulus, Ceriodaphnia dubia, and Daphnia pulex) of 100 ind. L−1. Filtered water from Xochimilco Lake was used to fill the mesocosms. Goodea atripinnis had a selective effect on the zooplankton community in the form of a decrease in the number of pelagic cladocerans. The zooplankton composition, which was least affected by the fish, included small-sized (400–480 µm) benthic cladocerans (e.g. Chydorus sphaericus) and copepods (both calanoids and cyclopoids). Prey consumption by the fish was highest under conditions with inorganic turbidity, while in the fishless treatments, small cladocerans (along with calanoids) had a high density. Organic turbidity offered refuge against fish predation to A. glabra, C. sphaericus, Daphnia pulex, M. alburquerquensis and A. americanus, whereas inorganic turbidity allowed only both test copepods to coexist in the presence of fish. The results suggest that fish predation is a powerful factor regulating zooplankton communities, even in highly turbid waters. [ABSTRACT FROM AUTHOR]

Despite the rapidly changing winter conditions in temperate ecosystems, little attention has been devoted to the effects of these changes on lake ecology. Few studies on the seasonal changes in abundance and biomass of the major groups of the metazooplankton community (i.e,. rotifers, cladocerans and copepods) in northern oligotrophic lakes include data from the ice-covered winter months. This study reports monthly variation in zooplankton abundance and biomass from June 2010 to October 2011, including winter, in an oligotrophic, subalpine lake in southeastern Norway (Lake Atnsjøen). Changes in rotifer, cladoceran, copepod, and total zooplankton abundances and biomass were related to seasonal variation in water temperature and phytoplankton biomass by means of ordination analysis. The zooplankton abundance and biomass were much lower in winter than during the open water season. However, an underice phytoplankton bloom occurred during the final winter months, when snow cover and ice thickness were reduced and (presumably) light penetration increased, leading to an increase in abundance of copepod nauplii. Winter zooplankton abundance was dominated by copepods and rotifers, while winter zooplankton biomass was dominated by copepods and cladocerans. Both phytoplankton and zooplankton had two biomass peaks in 2010 and one peak in 2011. Rotifers dominated zooplankton abundance with a peak in August and total zooplankton abundance followed a similar pattern. In contrast, cladocerans dominated zooplankton biomass with a peak in July and total zooplankton biomass also peaked at this time. Rotifer and total zooplankton abundance and rotifer biomass were most closely correlated to water temperature. However, cladoceran biomass and total biomass were most closely correlated with phytoplankton biomass, but also appeared to be dependent on other carbon sources. Estimates of non-phytoplankton particulate organic carbon indicated that this part of the carbon pool could be an additional food source for zooplankton particularly in early and mid-winter. The longer growing season in 2011 than in 2010, owing to earlier ice-off in 2011, may have contributed to higher phytoplankton and zooplankton biomass in 2011. With climate warming, this is an expected change in temperate lake ecosystems. [ABSTRACT FROM AUTHOR]

Spring and summer open-water crustacean zooplankton communities were examined across all five Laurentian Great Lakes from 1997 to 2016. Spring communities were dominated by calanoid (lakes Superior, Huron and Michigan) or cyclopoid (lakes Erie and Ontario) copepods. Volumetric biomass of summer communities increased along an assumed trophic gradient (Superior, Huron, Michigan, Ontario; eastern, central and western Erie), as did dominance by cyclopoids and cladocerans. Over the time series of the study, summer communities in lakes Michigan, Huron and Ontario shifted towards greater dominance by calanoids and greater similarity with Lake Superior. Trajectories of changes were different; however, reductions in cladocerans accounted for most of the change in lakes Michigan and Huron while reductions in cyclopoids and increases in Leptodiaptomus sicilis were behind the changes in Lake Ontario. Shifts in the predatory cladoceran community in Lake Ontario from Cercopagis pengoi to occasional dominance by Bythotrephes longimanus , a species much more vulnerable to planktivory, as well as the appearance of Daphnia mendotae in a daphnid community previously consisting almost exclusively of the smaller Daphnia retrocurva , suggest impacts of reduced vertebrate predation. In contrast, strong correlations between cladocerans and chlorophyll in lakes Michigan and Huron point to the possible importance of bottom-up forces in those lakes. Large interannual shifts in cladoceran community structure in the central and eastern basins of Lake Erie suggest intense but variable vertebrate predation pressure. The zooplankton communities of lakes Huron, Michigan and Ontario may be approaching a historic community structure represented by Lake Superior. [ABSTRACT FROM AUTHOR]

Functional-approach studies are currently increasing in ecology. However, for zooplankton communities, studies are mostly concentrated in marine environments. This study provides a systematic review to reveal the trends and gaps in scientific literature regarding zooplankton functional-approach in continental aquatic environments, including its main groups (testate amoebas, cladocerans, copepods, and rotifers). We focused on determining which functional traits were evaluated for these groups and whether they were based on direct measurements or on literature. We found that despite the recent increase in publications, most studies were limited to Canada, USA, Brazil, and Italy. Publications have been increasing over the last 3 years, representing an advance toward the understanding of the dynamics of these organisms in relation to environmental variations. Most studies used size-related functional traits. Nonetheless, other studies that deal with dietary and feeding strategies have improved the understanding of the dynamics of these organisms. Therefore, we highlight that the use of functional approach is an important tool to understand ecosystem processes and thus to contribute to the knowledge of biodiversity conservation and ecosystem dynamics. [ABSTRACT FROM AUTHOR]

Cyclomorphosis is a temporal, cyclic or induced morphological change that occurs in the planktonic population, primarily as the outcome of abiotic or biotic factors in the environment. This phenomenon is noted in the dinoflagellates, rotifers, cladocerans and much strikingly in the copepods. In this study, search engines like the Google Scholar, National Science Library, PubMed and journal sites like the journal of freshwater biology were used for the literature search. Search terms include aquatic ecosystem, cyclomorphosis, rotifers, cladocerans, zooplankton, copepods and dinoflagellates. Detailed evidence-based literature was used to review the adaptive mechanisms of cyclomorphosis in an aquatic ecosystem. The research results suggest that the change that occurs in the lorica, size and number of outer ornamentation like spines and the shape of mastax in accordance to body shape is remarkable in zooplankton. The degree to cyclomorphosis which is developed within different populations of the same species is variable. Organisms can produce cyclomorphic variability in the tropical and subtropical regions as there is sufficient temperature difference among the seasons. The total body size may increase, decrease or remain the same throughout the cycle, depending on the species. Organisms produce exuberances that are not retained in all generations. However, little attention has been previously given to the non-exuberant side of cyclomorphosis. This review concludes that studies in cyclomorphosis are gradually going into extinction, as most of the works done were carried out in the past. Hence, the need for a revival of cyclomorphic research interest in this part of the world. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate planktonic microcrustacean species composition, abundance, and diversity in lakes with different trophic status and to determine the relationship between microcrustacean community structure and lake environmental conditions. This study hypothesized that there are correlations between eutrophication levels and microcrustacean community structures in a lake. Three shallow lakes of different trophic status (Sembrong, Putrajaya and Subang lakes) were selected for this study. Two-Way Analysis of similarities (ANOSIM) revealed differences in microcrustacean diversity and density amongst lakes, where the hypereutrophic condition in Sembrong lake resulted in the lowest diversity but the highest density of microcrustaceans. Similarity percentage (SIMPER) analysis identified the discriminator species among lakes where the domination of small-sized microcrustaceans was observed in lakes with high levels of eutrophication; the hypereutrophic Sembrong lake (Ceriodaphnia cornuta, 74.0%); the meso-eutrophic Putrajaya lake (Bosmina longirostris, 46.9%; C. cornuta, 19.4%). Chlorophyll a, total phosphorus and water transparency showed significant roles in the distribution of microcrustaceans. The canonical correspondence analysis (CCA) scores indicated that small-sized C. cornuta and B. longirostris were related to the eutrophic conditions of lakes. This study elucidated that the lake trophic status could be one of the main factors contributing to the community restructuring of microcrustaceans in tropical lakes.

Nitrogen (N) and phosphorus (P) limit primary production in many aquatic ecosystems, with major implications for ecological interactions in plankton communities. Yet it remains unclear how evolution may affect the N∶P stoichiometry of phytoplankton-zooplankton interactions. Here, we address this issue by analyzing an eco-evolutionary model of phytoplankton-zooplankton interactions with explicit nitrogen and phosphorus dynamics. In our model, investment of phytoplankton in nitrogen versus phosphorus uptake is an evolving trait, and zooplankton display selectivity for phytoplankton with N∶P ratios matching their nutritional requirements. We use this model to explore implications of the contrasting N∶P requirements of copepods versus cladocerans. The model predicts that selective zooplankton strongly affect the N∶P ratio of phytoplankton, resulting in deviations from their optimum N∶P ratio. Specifically, selective grazing by nitrogen-demanding copepods favors dominance of phytoplankton with low N∶P ratios, whereas phosphorus-demanding cladocerans favor dominance of phytoplankton with high N∶P ratios. Interestingly, selective grazing by nutritionally balanced zooplankton leads to the occurrence of alternative stable states, where phytoplankton may evolve either low, optimum, or high N∶P ratios, depending on the initial conditions. These results offer a new perspective on commonly observed differences in N∶P stoichiometry between plankton of freshwater and those of marine ecosystems and indicate that selective grazing by zooplankton can have a major impact on the stoichiometric composition of phytoplankton. [ABSTRACT FROM AUTHOR]

We assessed the zooplankton assemblages in four temperate shallow waterbodies differing in macrophyte coverage and alternative states: transparent vs . turbid. The main objectives of this study were: (i) to determine the horizontal assemblage of zooplankton in structurally different habitats; (ii) to examine the role of fish, macroinvertebrates and environmental conditions in the observed zooplankton assemblage patterns; and (iii) to evaluate the zooplankton-macroinvertebrate-fish food web interactions in pelagial and littoral zone in transparent vs . turbid lakes. Abiotic factors and food resources, as well as zooplankton assemblage did not show significant difference along the gradient of habitat complexity, but exhibited pronounced variability among these waterbodies. Selected lakes contained nutrient levels that can undergo or were shifted into turbid state. Two waterbodies showed hysteresis: at similar nutrient conditions one remained transparent with macrophytes, while other shifted in its turbid state with increased phytoplankton biomass, and reduced population of planktonic crustaceans. Rotifers contributed mainly to the metazooplankton diversity and abundance. The results suggested that total phosphorous and phytoplankton were the main drivers in turbid waterbodies, and biotic interactions governed structuring of zooplankton assemblage in transparent waterbodies. Habitats of submerged and floating-leaved macrophytes do not appear to a secure refuge for zooplankton against predation. On the other hand, sediment in the vegetated and non-vegetated littoral zone functioned as an effective shelter. According to our results, zooplankton underwent strong predation pressure by macroinvertebrates and small-sized fish in the littoral and by larger-sized fish in pelagial, with alteration related to ecosystem peculiarities. Based on an applied ecological network model, zooplankters were equally vulnerable to predation in both the pelagial and littoral zones, and these biotic interactions were main factors for zooplankton homogenous horizontal distribution. These results suggest that zooplankton organisms play important role in the matter cycling and resilience of the food webs to environmental alterations. [ABSTRACT FROM AUTHOR]

The crustaceans of non-marine environments on Chilean oceanic islands have been poorly studied, principally due to their geographical isolation and difficult access. The aim of this study is to present a checklist of non-marine (non-hexapod) crustaceans on Chilean oceanic islands based on a review of the literature, with hopes of stimulating further research on this poorly known fauna. The checklist includes records of 27 species from Easter Island and the Juan Fernández Island archipelago, and reveals an absence of records from Sala y Gómez, San Ambrosio, and San Felix Islands. [ABSTRACT FROM AUTHOR]

A major attribute of the Earth's climate that may be affected by global warming is the amplitude of variability in teleconnections. These global-scale processes involve links between oceanic conditions in one locale and weather in another, often distant, locale. An example is the El Niño Southern Oscillation (ENSO), which can affect rainfall and then the properties of lakes in Europe, Africa, North and South America. It affects rainfall, droughts and the depth of lakes in Florida, USA. It is predicted that the amplitude of variation in the ENSO will increase with global warming and, therefore, droughts will become more severe and periods of rain more intense. We investigated possible effects of climate on the zooplankton in shallow subtropical lakes by studying 16 years of monthly data from six shallow eutrophic lakes located north of Orlando, Florida. Results indicate that water depth and lake volume are tightly coupled with rainfall, as expected. During droughts, when lake depth and volume were greatly reduced, there were intensified cyanobacterial blooms, and the zooplankton shifted towards greater relative biomass of copepods compared to cladocerans. The change of zooplankton was likely due to the intensified selective fish predation in the reduced water volume, and/or selective adverse effects of cyanobacteria on cladocerans. The greatly reduced volume might lead to a 'perfect storm' of top-down and bottom-up factors that favor copepods over cladocerans. The mechanism needs further study. Regardless, this study documents a direct link between climate variability and zooplankton composition, and suggests how future changes in climate might affect plankton communities. [ABSTRACT FROM AUTHOR]

We investigated the relative importance of flood defenses and other environmental variables for the cladoceran and copepod communities in floodplain water bodies in Southeastern Norway. The water bodies covered gradients of size, distance to the river and water chemistry, and half of them were located behind flood defenses. The effects of environmental variables on the communities were analyzed using redundancy analysis. The set of environmental variables accounted for more of the explained variation in the cladoceran community than in the copepod community. Water quality was much more important than flooding-related variables for both communities. Although cladoceran species richness was slightly higher in water bodies outside flood defenses, total nitrogen, total organic carbon (TOC), and water body area were the most important factors for the cladocerans. Macrophyte coverage was the most important variable for both species richness and community structure of copepods. Although our results show that water quality and spatial/structural variables are more important than flood defenses in structuring the communities, the effect of TOC on the cladoceran community could likely be mediated through effects of flood defense on TOC. Prospects for a continued anthropogenic pressure on river floodplains raise concern for the future of these unique ecosystems. [ABSTRACT FROM AUTHOR]

The effects of cyanobacteria on zooplankton abundance, structure and diversity were investigated, based on a systematic study on spatial and temporal variations of cyanobacteria and zooplankton in Lake Taihu from 1998 to 2007. It was found that similar increasing trends of cyanobacteria/phytoplankton ratios were accompanied by different trends in biomass, composition and biodiversity of zooplankton in different regions of the lake; the cladocerans benefitted from the increase in cyanobacteria; however, rotifers and protozoans were negatively affected by cyanobacteria. The biomass-based biodiversity of phytoplankton and zooplankton was negatively affected by cyanobacteria as well, and the adverse effects were in proportion to the cyanobacteria/phytoplankton ratio. These results indicated interestingly that higher amounts of cyanobacteria do not necessarily reduce zooplankton biomass, as the biomass of larger zooplankton such as cladocerans was positively related to cyanobacteria. The findings are essential to understand the complex ecological effects of cyanobacteria blooms in lakes. [ABSTRACT FROM AUTHOR]

The focus of this study is to investigate if microcrustaceans undergo diel horizontal migration (DHM) in a tropical shallow lake on a yearly basis and analyse the adaptive value regarding predation. Abundance of invertebrate predators, chaoborid larvae and water mites, and microcrustaceans (cladocerans and copepods) were evaluated on a monthly basis in three stations located on a transect during the day and at night. Both invertebrate predators were predominantly pelagic. Cladocerans did not undergo significant DHM, distributing indistinctly onshore and offshore or being mostly pelagic. Nauplii, copepodites of two copepod species and adults of Tropocyclops prasinus meridionalis Kiefer were mostly distributed offshore, and did not perform DHM. The limnological features (temperature, dissolved oxygen, pH, and conductivity) were suitable for the organisms in both zones of the lake. Algal food concentration was a little lower in the littoral than in the limnetic zone during the day, but it seems to be suitable for the organisms. However, as the algae quality was not evaluated, it is not possible to be conclusive concerning its influence. The results indicated that DHM was not performed by the microcrustaceans and is not, therefore, a strategy for decreasing predation by both invertebrates, Chaoborus brasiliensis Theobald and Krendowskia sp., on a yearly basis in this shallow lake.O foco deste estudo é verificar se microcrustáceos apresentam migração horizontal diária (MHD) em um lago raso tropical, durante um ano, e o valor adaptativo com relação à predação. A abundância de predadores invertebrados, larvas de caoborídeos e ácaros aquáticos, e de cladóceros e copépodos foi avaliada mensalmente em três estações de coleta localizadas em um transecto, de dia e à noite. Ambos os predadores invertebrados foram predominantemente pelágicos. Os cladóceros não realizaram MHD, distribuindo-se indistintamente nas zonas litorânea e pelágica, ou foram mais abundantes na zona limnética. Os náuplios e copepoditos de duas espécies de copépodos e os adultos de Tropocyclops prasinus meridionalis Kiefer ocuparam principalmente a zona limnética, não migrando horizontalmente. As características limnológicas (temperatura, oxigênio dissolvido, pH e condutividade) foram adequadas nas duas zonas do lago. A concentração de alga foi um pouco menor no litoral do que na zona limnética durante o dia e parece ser adequada para os organismos; contudo, como a qualidade das algas não foi avaliada, não é possível ser conclusivo sobre sua influência. Os resultados indicaram que os microcrustáceos não realizaram MHD, a qual não constitui, portanto, uma estratégia para diminuir a predação dos dois invertebrados, Chaoborus brasiliensis Theobald e Krendowskia sp., em uma base anual, neste lago raso.