Functional Groups Of Zooplankton Research Articles

How do environmental variables affect the temporal dynamics of zooplankton functional groups in a hyper-eutrophic wetland?

In recent years, trait-based research on zooplankton has gained importance to enable comprehensive interpretation of ecosystem processes, but this approach is still limited in inland waters. Wetlands, one of the most important inland water resources, provide many ecological and economic services in the ecosystem, but like all other water bodies in the world, they are under threat of deterioration and depletion for various reasons. In this study, the taxonomic structure of the zooplankton community in Lake Manyas, one of the important wetlands of Türkiye, as well as their functional characteristics such as body size (small, large) and feeding strategies (microphagous, raptorials) were investigated monthly between 2019 and 2020. The hypothesis that environmental variables influence the species composition and functional groups of zooplankton was tested, given that their structure is shaped by environmental gradients. A total of 62 taxa, including rotifer-dominated, cosmopolite and eutrophication indicator species, were identified. These taxa categorized into three functional groups dominated by small microphagous. Although the zooplankton structure had a high taxonomic diversity, functional homogeneity was observed which reflected a low grazing rate in the ecosystem. Albeit water temperature and total organic carbon significantly affected the distribution of all functional groups, each dominant taxa interacted with different environmental variables. Changing environmental conditions in the lake affected the presence and/or quantity of the zooplankton functional groups (ZFGs). The results showed that ZFGs are strongly associated with environmental conditions and that the response of trait-based functional groups to environmental changes can provide useful knowledge about aquatic ecosystem's health.

Footprint of the plastisphere on freshwater zooplankton

Changes in the functional groups of zooplankton were studied in autumn in a temperate floodplain lake (Lake Sakadaš, Kopački Rit Nature Park, Croatia) and in the Drava River (in the Croatian part of the river). Various abiotic parameters as well as available food sources (phytoplankton and microphytes (algae and cyanobacteria) developing on epixylon, epilithon and artificially introduced microplastics called “plastisphere”) were also studied. The lake was hydrologically isolated from the main river during the study, while the water level of the Drava River fluctuated, resulting in larger variations in limnological parameters. Due to stable conditions in the lake, zooplankton abundance, biomass, and species richness were higher than in the Drava River. In both environments, zooplankton species feeding on bacteria, detrital suspensions, and small algae were most abundant, with predators and microfilter-feeders being more abundant in the lake. Microphytes were diverse and mostly small and medium-sized in phytoplankton and all substrate types. Stable lake conditions promoted higher abundance of the zooplankton group, which effectively uses larger algae as a food source. The lower abundance of zooplankton feeding on larger algae and predatory species in the river suggests that the epilithon and plastisphere community was a less mature community compared to the lake, and the heterotrophic component with ciliates and/or other small heterotrophs was not well developed. The importance of plastispheres was particularly evident under the turbid hydrologic conditions that prevailed in the river at the end of the study, when phytoplankton biomass decreased and zooplankton abundance steadily increased, suggesting that microphytes colonised on microplastics were an additional food source for higher trophic levels.

Grazing resistance and poor food quality of a widespread mixotroph impair zooplankton secondary production

Growing evidence suggests that global climate change promotes the dominance of mixotrophic algae especially in oligotrophic aquatic ecosystems. While theory predicts that mixotrophy increases trophic transfer efficiency in aquatic food webs, deleterious effects of some mixotrophs on consumers have also been reported. Here, using a widespread mixotrophic algal genus Dinobryon, we aimed to quantify how colonial taxa contribute to secondary production in lakes. We, therefore, studied the dietary effects of Dinobryon divergens on Cladocera (Daphnia longispina) and Copepoda (Eudiaptomus gracilis), representing two main taxonomic and functional groups of zooplankton. In feeding experiments, we showed that Dinobryon was largely grazing resistant and even inhibited the uptake of the high-quality reference food in Daphnia. Eudiaptomus could to some extent compensate with selective feeding, but a negative long-term food quality effect was also evident. Besides, Eudiaptomus was more sensitive to the pure diet of Dinobryon than Daphnia. Low lipid content and high C:P elemental ratio further supported the low nutritional value of the mixotroph. In a stable isotope approach analysing a natural plankton community, we found further evidence that carbon of Dinobryon was not conveyed efficiently to zooplankton. Our results show that the increasing dominance of colonial mixotrophs can result in reduced dietary energy transfer to consumers at higher trophic levels. In a wider perspective, global climate change favours the dominance of some detrimental mixotrophic algae which may constrain pelagic trophic transfer efficiency in oligotrophic systems, similarly to cyanobacteria in eutrophic lakes.

Variations in zooplankton functional groups density in freshwater ecosystems exposed to cyanobacterial blooms

The recently observed decline of biodiversity has become a major problem on Earth. Anthropogenically-driven climate change and eutrophication of natural habitats represent great threats to both terrestrial and aquatic ecosystems. Particularly vulnerable are freshwater ecosystems, where the mentioned changes promote development of cyanobacteria. Extension of the cyanobacterial bloom period, increase of cyanobacterial biomass production and toxicity may involve numerous changes in freshwater ecosystem functioning. We conducted a study in water bodies exposed to cyanobacterial blooms of different duration: short-lasting and long-lasting cyanobacterial blooms. We tested the impact of cyanobacterial biomass on densities of zooplankton species grouped into functional groups (functional groups densities) under conditions of different bloom length periods. The functional groups of zooplankton were identified on the basis of three functional traits of each species: mean body length (BL), potential food source (FS) and feeding type (FT). The results of the study showed that assembling species into functional groups may be helpful in understanding the interactions between biotic components of ecosystem. The results showed that the response of each functional group density for cyanobacterial biomass development depends on the functional traits of the animals (i.e. how the species interact with the whole food web) and may be different depending on the bloom intensity, which acts like a factor selecting adapted species.

Intra-annual variation of zooplankton community structure and dynamics in response to the changing strength of bio-manipulation with two planktivorous fishes

Zooplankton is widely used in indicating environmental changes and energy flow efficiency in aquatic ecosystems. Species composition and body size spectrum of zooplankton assemblage are sensitive to the changes of physico-chemical variability and fish feeding stress, and thus have in turn a prime bearing on water quality and cultured fishes. To study the response of zooplankton community to the introduction of planktivorous carps, monthly surveys were conducted in 2015 at six traditionally monitored locations in Miyun Reservoir, the unique surface drinking water of Beijing. There was a decrease in species richness, diversity, density and biomass, suggesting simplification of the community structure. Species diversity, density, and biomass declined significantly through the growth season, illustrating the great pressure imposed on the zooplankton. Regression and canonical correspondence analysis (CCA) showed low relationships between community traits and environmental variables. Zooplankton biomass had a significantly negative relationship with the stocking intensity of the filter-feeding carp. The different responses of the subgroups of Protozoa, Rotifera, Cladocera and Copepoda indicated that they responded differently to environmental stress. Seasonal variations in the density and biomass of the four subgroups and biomass size spectrum (BSS) indicated that planktons with medium and large body sizes were more sensitive and suffered more stress from the filter-feeding carp. The filter feeding by the silver and bighead carp disrupted the natural equilibrium of the zooplankton community, decreased diversity and stocks, altered the seasonal dynamics of all quantitative traits and suppressed the dominance of medium- and large-sized species or functional groups. The impacts of the fishery mode and the responses of different functional groups of zooplankton must be considered in ecological assessments and biomanipulation studies based on the zooplankton community structure and dynamics.

Bottom-up linkages between primary production, zooplankton, and fish in a shallow, hypereutrophic lake.

Nutrient supply is a key bottom-up control of phytoplankton primary production in lake ecosystems. Top-down control via grazing pressure by zooplankton also constrains primary production and primary production may simultaneously affect zooplankton. Few studies have addressed these bidirectional interactions. We used convergent cross-mapping (CCM), a numerical test of causal associations, to quantify the presence and direction of the causal relationships among environmental variables (light availability, surface water temperature, NO3 -N, and PO4 -P), phytoplankton community composition, primary production, and the abundances of five functional zooplankton groups (large cladocerans, small cladocerans, rotifers, calanoids, and cyclopoids) in Lake Kasumigaura, a shallow, hypereutrophic lake in Japan. CCM suggested that primary production was causally influenced by NO3 -N and phytoplankton community composition; there was no detectable evidence of a causal effect of zooplankton on primary production. Our results also suggest that rotifers and cyclopoids were forced by primary production, and cyclopoids were further influenced by rotifers. However, our CCM suggested that primary production was weakly influenced by rotifers (i.e., bidirectional interaction). These findings may suggest complex linkages between nutrients, primary production, and rotifers and cyclopoids, a pattern that has not been previously detected or has been neglected. We used linear regression analysis to examine the relationships between the zooplankton community and pond smelt (Hypomesus nipponensis), the most abundant planktivore and the most important commercial fish species in Lake Kasumigaura. The relative abundance of pond smelt was significantly and positively correlated with the abundances of rotifers and cyclopoids, which were causally influenced by primary production. This finding suggests that bottom-up linkages between nutrient, primary production, and zooplankton abundance might be a key mechanism supporting high planktivore abundance in eutrophic lakes. Because increases in primary production and cyanobacteria blooms are likely to occur simultaneously in hypereutrophic lakes, our study highlights the need for ecosystem management to resolve the conflict between good water quality and high fishery production.

Plankton community patterns across a trophic gradient: The role of zooplankton functional groups

We use a complex aquatic biogeochemical model to examine competition patterns and structural shifts in plankton communities under nutrient enrichment conditions. Our model simulates multiple elemental cycles (organic C, N, P, Si, O), multiple functional phytoplankton (diatoms, green algae and cyanobacteria) and zooplankton (copepods and cladocerans) groups. The model provided a realistic platform to examine the functional properties (e.g., grazing strategies, food quality, predation rates, stoichiometry, basal metabolism, and temperature requirements) and the abiotic conditions (temperature, nutrient loading) under which the different plankton groups can dominate or can be competitively excluded in oligo-, meso- and eutrophic environments. Our analysis shows that the group-specific maximum grazing rates, the predation rates from planktivorous fish, along with the temperature requirements to attain optimal growth can be particularly influential on the structure of plankton communities. The model also takes into account recent advances in stoichiometric nutrient recycling theory, which allowed examining the effects of the cyanobacteria food quality, the critical threshold for mineral P limitation, and the half saturation constant for assimilation efficiency on the zooplankton functional group biomass across a range of nutrient loading conditions. Our study highlights the adverse effects that the cyanobacteria food quality can have on the two functional zooplankton groups in productive systems, despite the differences in their feeding selectivity strategies, i.e., cladocerans are filter-feeders with equal preference among the different types of food, whereas copepods are assumed to be capable of selecting on the basis of food quality. Finally, we conclude that the articulate representation of the producer–grazer interactions using stoichiometrically/biochemically realistic terms will offer insights into the patterns of nutrient and energy flow transferred to the higher trophic levels.

Response of zooplankton to nutrient enrichment and fish in shallow lakes: a pan‐European mesocosm experiment

Summary1. Responses of zooplankton to nutrient enrichment and fish predation were studied in 1998 and 1999 by carrying out parallel mesocosm experiments in six lakes across Europe.2. Zooplankton community structure, biomass and responses to nutrient and fish manipulation showed geographical and year‐to‐year differences. Fish had a greater influence than nutrients in regulating zooplankton biomass and especially the relative abundances of different functional groups of zooplankton. When fish reduced the biomass of large crustaceans, there was a complementary increase in the biomasses of smaller crustacean species and rotifers.3. High abundance of submerged macrophytes provided refuge for zooplankton against fish predation but this refuge effect differed notably in magnitude among sites.4. Large crustacean grazers (Daphnia, Diaphanosoma, Sida and Simocephalus) were crucial in controlling algal biomass, while smaller crustacean grazers and rotifers were of minor importance. Large grazers were able to control phytoplankton biomass even under hypereutrophic conditions (up to 1600 μg TP L−1) when grazer biomass was high (>80–90 μg dry mass L−1) or accounted for >30% of the grazer community.5. The littoral zooplankton community was less resistant to change following nutrient enrichment in southern Spain, at high temperatures (close to 30 °C), than at lower temperatures (17–23 °C) characterising the other sites. This lower resistance was because of a greater importance of nutrients than zooplankton in controlling algal biomass.6. Apart from the reduced role of large crustacean grazers at the lowest latitude, no consistent geographical patterns were observed in the responses of zooplankton communities to nutrient and fish manipulation.

COMPENSATORY DYNAMICS IN ZOOPLANKTON COMMUNITY RESPONSES TO ACIDIFICATION: MEASUREMENT AND MECHANISMS

Previous studies indicate substantial variation in ecological responses to perturbation. In some cases, ecosystems are resilient to perturbation due to compensatory dynamics in which losses of sensitive species are offset by population increases of species that perform similar ecological functions. Here, we report a detailed evaluation of compensatory dynamics in zooplankton community responses to the experimental acidification of Little Rock Lake, Wisconsin, USA. We used a variance ratio to quantify compensatory dynamics in functional groups of zooplankton containing species that use similar resources and are vulnerable to the same predators. We also used first-order autoregressive models to explore mechanisms driving the dynamics of each functional group. Our results indicate that responses of functional groups to acidification can be highly variable. Herbivorous copepods and medium-sized herbivorous cladocerans exhibited significant compensatory dynamics in response to acidification, whereas other functional groups exhibited independent or synchronous dynamics. First-order autoregressive models indicated that groups exhibiting compensatory dynamics contained both acid-tolerant and acid-sensitive species that competed. In contrast, groups that contained only acid-sensitive or acid-tolerant species exhibited more independent or synchronous dynamics. Overall, our study highlights the combined roles of sensitivity to environmental perturbation and species interactions in determining the extent of compensatory dynamics in zooplankton functional group responses to acidification.