Filter-feeding Zooplankton Research Articles

Combined effects of climate warming and pharmaceuticals on a tri-trophic freshwater food web

Multiple anthropogenic stressors influence the functioning of lakes and ponds, but their combined effects are often little understood. We conducted two mesocosm experiments to evaluate the effects of warming (+4 °C above ambient temperature) and environmentally relevant concentrations of a mixture of commonly used pharmaceuticals (cardiovascular, psychoactive, antihistamines, antibiotics) on tri-trophic food webs representative of communities in ponds and other small standing waters. Communities were constituted of phyto- and zooplankton and macroinvertebrates (molluscs and insects) including benthic detritivores, grazers, omnivorous scrapers, omnivorous piercers, water column predators, benthic predators, and phytophilous predators. We quantified the main and interactive effects of warming and pharmaceuticals on each trophic level in the pelagic community and attributed them to the direct effects of both stressors and the indirect effects arising through biotic interactions. Warming and pharmaceuticals had stronger effects in the summer experiment, altering zooplankton community composition and causing delayed or accelerated emergence of top insect predators (odonates). In the summer experiment, both stressors and top predators reduced the biomass of filter-feeding zooplankton (cladocerans), while warming and pharmaceuticals had opposite effects on phytoplankton. In the winter experiment, the effects were much weaker and were limited to a positive effect of warming on phytoplankton biomass. Overall, we show that pharmaceuticals can exacerbate the effects of climate warming in freshwater ecosystems, especially during the warm season. Our results demonstrate the utility of community-level studies across seasons for risk assessment of multiple emerging stressors in freshwater ecosystems.

Climate-driven zooplankton shifts cause large-scale declines in food quality for fish

Zooplankton are the primary energy pathway from phytoplankton to fish. Yet, there is limited understanding about how climate change will modify zooplankton communities and the implications for marine food webs globally. Using a trait-based marine ecosystem model resolving key zooplankton groups, we find that future oceans, particularly in tropical regions, favour food webs increasingly dominated by carnivorous (chaetognaths, jellyfish and carnivorous copepods) and gelatinous filter-feeding zooplankton (larvaceans and salps) at the expense of omnivorous copepods and euphausiids. By providing a direct energetic pathway from small phytoplankton to fish, the rise of gelatinous filter feeders partially offsets the increase in trophic steps between primary producers and fish from declining phytoplankton biomass and increases in carnivorous zooplankton. However, future fish communities experience reduced carrying capacity from falling phytoplankton biomass and less nutritious food as environmental conditions increasingly favour gelatinous zooplankton, slightly exacerbating projected declines in small pelagic fish biomass in tropical regions by 2100.

Integrated application of macrophytes and zooplankton for wastewater treatment

The increasing amount of sewage has become a serious concern globally, demanding sustainable solutions. The constructed wetland system (CWS) can be installed at the wastewater discharge site and properly screened bio-purifiers can be used for efficient wastewater treatment. Filter-feeding zooplankton have the potential to graze on bacteria and reduce biological oxygen demand. However, higher suspended particles choke the zooplankton filtering appendages. An integrated application of zooplankton and macrophytes can solve the problems by reducing contaminants and providing the surface area for zooplankton to take refuge. Using three different approaches: (a) screening of natural bio-purifiers through time series study, (b) assessment of sewage treatment potential of screened bio-purifiers in the CWS and, (c) evaluation of the growth potential of screened bio-purifiers in untreated wastewater, this study explored the combined use of macrophyte and zooplankton in the CWS. The 3-year time series study in the vicinity of the wastewater discharge area recorded the zooplankton, Brachionus angularis and Moina macrocopa as highly indicative zooplankton. The top two highly indicative macrophytes are Typha and Phragmites. Under laboratory conditions, the population growth rates of B. angularis and M. macrocopa were significantly higher in wastewater without any external nutrient source than those in control with algae as a food source. The integrated application of zooplankton (B. angularis and M. macrocopa) macrophytes (Typha and Phragmites) in CWS yielded upto 56% reduction in the total bacterial count and upto 92% reduction in BOD along with substantial increase in the DO level. The present results strongly suggested the use of CWS planted with macrophytes and inoculated by zooplankton. The usefulness of this system is further supported by the natural occurrence of selected species, as it is easy to maintain, has low installation cost, and excellent efficiency in treating wastewater. As both the zooplankton species are preferred live feed for rearing of fish larvae, the present results suggested the use of zooplankton and macrophytes for treatment of wastewater, reduction of sludge, and harvest of live feeds for the aquaculture industry to augment circularity and promote decentralized wastewater treatment.

Water Chemistry, Exposure Routes, and Metal Forms Determine the Bioaccumulation Dynamics of Silver (Ionic and Nanoparticulate) in Daphnia magna.

Treatment wetlands utilize various physical and biological processes to reduce levels of organic contaminants, metals, bacteria, and suspended solids. Silver nanoparticles (AgNPs) are one type of contaminant that can enter treatment wetlands and impact the overall treatment efficacy. Grazing by filter-feeding zooplankton, such as Daphnia magna, is critical to treatment wetland functioning; but the effects of AgNPs on zooplankton are not fully understood, especially at environmentally relevant concentrations. We characterized the bioaccumulation kinetics of dissolved and nanoparticulate (citrate-coated) 109 Ag in D. magna exposed to environmentally relevant 109 Ag concentrations (i.e., 0.2-23 nmol L-1 Ag) using a stable isotope as a tracer of Ag. Both aqueous and nanoparticulate forms of 109 Ag were bioavailable to D. magna after exposure. Water chemistry affected 109 Ag influx from 109 AgNP but not from 109 AgNO3 . Silver retention was greater for citrate-coated 109 AgNP than dissolved 109 Ag, indicating a greater potential for bioaccumulation from nanoparticulate Ag. Feeding inhibition was observed at higher dietary 109 Ag concentrations, which could lead to reduced treatment wetland performance. Our results illustrate the importance of using environmentally relevant concentrations and media compositions when predicting Ag bioaccumulation and provide insight into potential effects on filter feeders critical to the function of treatment wetlands. Environ Toxicol Chem 2022;41:726-738. © 2021 SETAC.

Transfer of Antibiotic Resistance Genes from a Waste Water Treated Plant Effluent to the Filter Feeding Zooplankton Daphnia Magna and its Associated Microbiome

Transfer of Antibiotic Resistance Genes from a Waste Water Treated Plant Effluent to the Filter Feeding Zooplankton Daphnia Magna and its Associated Microbiome

Transfer of Antibiotic Resistance Genes from a Waste Water Treated Plant Effluent to the Filter Feeding Zooplankton Daphnia Magna and its Associated Microbiome

Transfer of Antibiotic Resistance Genes from a Waste Water Treated Plant Effluent to the Filter Feeding Zooplankton Daphnia Magna and its Associated Microbiome

Biogenic Aggregation of Small Microplastics Alters Their Ingestion by a Common Freshwater Micro-Invertebrate

In recent years, increasing concerns have been raised about the environmental risk of microplastics in freshwater ecosystems. Small microplastics enter the water either directly or accumulate through disintegration of larger plastic particles. These particles might then be ingested by filter-feeding zooplankton, such as rotifers. Particles released into the water may also interact with the biota through the formation of aggregates, which might alter the uptake by zooplankton. In this study, we tested for size-specific aggregation of polystyrene microspheres and their ingestion by a common freshwater rotifer Brachionus calyciflorus. The ingestion of three sizes of polystyrene microspheres (MS) 1-, 3-, and 6-μm was investigated. Each MS size was tested in combination with three different treatments: MS as the sole food intake, MS in association with food algae and MS aggregated with biogenic matter. After 72 h incubation in pre-filtered natural river water, the majority of the 1-μm spheres occurred as aggregates. The larger the particles, the higher the relative number of single particles and the larger the aggregates. All particles were ingested by the rotifer following a Type-II functional response. The presence of algae did not influence the ingestion of the MS for all three sizes. The biogenic aggregation of microspheres led to a significant size-dependent alteration in their ingestion. Rotifers ingested more microspheres (MS) when exposed to aggregated 1- and 3-μm MS as compared to single spheres, whereas fewer aggregated 6-μm spheres were ingested. This indicates that the small particles when aggregated were in an effective size range for Brachionus, while the aggregated larger spheres became too large to be efficiently ingested. These observations provide the first evidence of a size- and aggregation-dependent feeding interaction between microplastics and rotifers. Microplastics when aggregated with biogenic particles in a natural environment can rapidly change their size-dependent availability. The aggregation properties of microplastics should be taken into account when performing experiments mimicking the natural environment.

Changes in Zooplankton Structure in an Experimental System at the Isolation of Plankton-Eating Fish

The trophic press of fish in a highly trophic pond causes a loss of species diversity and a decrease in the organism size of filter-feeding zooplankton. The isolation of fish from an experimental flow-through system leads to increases in abundance and biomass of large-size zooplankton. The rate of alga and cyanobacteria consumption by zooplankton increases as does its fertility and organism size. The result is the removal of cyanobacteria from water in the flow-through ecosystem and recovery of the water quality.

Microplastic exposure to zooplankton at tidal fronts in Charleston Harbor, SC USA

Zooplankton, fish, marine mammals and birds forage at flood-tide front aggregation zones that form at the mouths of the Ashley and Cooper Rivers in Charleston Harbor, South Carolina USA where semi-buoyant particulates and phytoplankton accumulate. Increased trophodynamics and the potential for the accumulation of semi-buoyant microplastic particles at aggregation zones may present a pathway of increased exposure for microplastic to enter the estuarine trophic system via ingestion by zooplankton. Optical and fluorescence microscopy were used to enumerate microplastic fiber and fragment concentrations, with melting point analysis applied for confirmation, in water sieved (sized 43–104 μm) from the upper meter of the water column at positions across tidal fronts. The Cooper River front contained significantly higher microplastic water concentrations, dominated by fragments, on the riverside and within the frontal zone versus the seaward side, indicating an input of microplastic from land-based sources. No significant increase in abundance of zooplankton was found within the Cooper River or Ashley River fronts. Microplastic in the gut of field-collected zooplankton was observed using fluorescence microscopy. Only zooplankton from the Cooper River were observed with ingested microplastic. Absence of detection in zooplankton from the Ashley River may be due to fibers being more prevalent than fragments in surface waters at that front. On average, 1% of the filter-feeding zooplankton observed contained ingested microplastic particles suggesting zooplankton may be selectively feeding. Although the fraction was small, it represents significant exposure to microplastic for pelagic fish species that may be feeding at flood-tidal fronts in Charleston Harbor.

Zooplankters' nightmare: The fast and efficient catching basket of larval phantom midges (Diptera: Chaoborus).

Filter feeding zooplankton are a crucial component of limnic food webs. Copepods and cladocerans are important prey organisms for first-level predators like the common and abundant larvae of phantom midges (Chaoborus sp.). The latter possess a complex catching basket built of head appendages specialized to capture small crustaceans. The predator-prey-relationship of Chaoborus (Diptera, Nematocera) and Daphnia (Crustacea, Cladocera) has been studied in particular detail owing to the daphniids’ ability to react upon the threat of predation with inducible defenses. Daphnia pulex expresses so-called ‘neckteeth’ in the presence of Chaoborus larvae that are discussed as a defensive trait that interferes with the larval head appendages and their effectiveness has been shown in several studies. Nonetheless, mode of function of these neckteeth is not understood and the hypothesis that they interfere with the predator’s head appendages still has to be confirmed. To clarify the role of neckteeth in Daphnia, an understanding of the Chaoborus capture apparatus is essential. Here, we present a detailed three-dimensional analysis of Chaoborus obscuripes’ larval head morphology as well as a kinematic analysis of the attack motion, which revealed an impressive strike velocity (14 ms to prey contact). The movement of the larvae’s head appendages is reconstructed in the three-dimensional space using a combination of high-speed videography, micro-computed tomography and computer animation. Furthermore, we provide predation trial data to distinguish between pre- and post-attack defensive effects in D. pulex. Our findings suggest a combination of pre- and post-attack defenses with an average effectiveness of 50% each. With this study, we quantitatively describe prey capture kinematics of C. obscuripes and take a further step to reveal the neckteeth’ mode of function in D. pulex.

Transfer of antibiotic resistance genes between Enterococcus faecalis strains in filter feeding zooplankton Daphnia magna and Daphnia pulex

Antibiotic resistant bacteria from faecal pollution sources are pervasive in aquatic environments. A facilitating role for the emergence of waterborne, multi-drug resistant bacterial pathogens has been attributed to biofiltration but had not yet been substantiated. This study investigated the effect of filtration and gut passage in Daphnia spp. on conjugal transfer of resistance genes in Enterococcus faecalis. In vivo conjugation experiments involved a vancomycin-resistant donor strain bearing a plasmid-borne vanA resistance gene, and two vancomycin-susceptible and rifampicin-resistant recipient strains in the presence of Daphnia magna or Daphnia pulex. Results showed successful transfer of the vanA resistance gene from donor to recipient; gene identity was confirmed by PCR and DNA sequencing. There was no significant difference in the number of transconjugants recovered from D. magna and D. pulex. However, transconjugant numbers differed by one order of magnitude between recipient strains. Transconjugant numbers from D. magna were also significantly different between treatments with ingestion of individual phytoplankton species before filtration of bacteria. The highest transfer efficiency calculated from excreted transconjugants was 2.5 × 10−6. This proof of concept for facilitation of horizontal gene transfer by a filter feeding organism provides evidence that Daphnia can disseminate antibiotic resistant transconjugants in the environment.

Fungal parasites of a toxic inedible cyanobacterium provide food to zooplankton

AbstractDuring the end of spring and throughout summer, large‐sized phytoplankton taxa often proliferate and form dense blooms in freshwater ecosystems. In many cases, they are inedible to zooplankton and prevent efficient transfer of energy and elements to higher trophic levels. Such a constraint may be alleviated by fungal parasite infections on large‐sized phytoplankton taxa like diatoms and filamentous cyanobacteria, as infections may provide zooplankton with a complementary food source in the form of fungal zoospores. Zoospores have been shown to support somatic growth of large filter feeding zooplankton species. Here, we tested if selectively feeding zooplankton, more specifically rotifers, also can use fungal zoospores as a food source. Our results show that chytrid fungal parasites can indeed support population growth of rotifers (Keratella sp.). Specifically, in cultures of an inedible filamentous cyanobacterium (Planktothrix rubescens), Keratella populations rapidly declined, while in Planktothrix cultures infected with chytrids, Keratella population growth rate equaled the growth observed for populations fed with a more suitable green algal diet (Chlorella sorokiniana). Feeding of Keratella on zoospores was furthermore indicated by a reduced number of zoospores during the last sampling day. These findings not only imply that rotifers may survive on zoospores, but also that the zoospores can support high rotifer population growth rates. We thus show that fungal parasites of inedible cyanobacteria can facilitate grazers by providing them alternative food sources. Together, these results highlight the important role that parasites may play in the aquatic plankton food web.

A comprehensive evaluation of Daphnia pulex foraging energetics and the influence of spatially heterogeneous food

Aquatic organisms are distributed in a heterogeneous, nonrandom manner, and zooplankton are known to seek out and orient themselves within regions of high food concentration. Yet, the energetics associated with this foraging behavior are unknown. We hypothesized that zooplankton foraging behavior increases foraging efficiency measured as food consumption per unit effort. In this study, we measured the energetic costs and benefits for the zooplankton Daphnia pulex foraging in a range of algal concentrations to determine the net energetic benefit of foraging in algal patches. The net energy benefit of foraging increased significantly with increases in algal concentration; this trend was driven by significant increases in prey ingestion with algal concentration, whereas foraging costs did not change. Even considering corrections for changes in assimilation efficiency, foraging in algal patches greatly increases net foraging benefit compared to foraging in low concentrations of algae and thus has the potential for higher reproduction and greater growth in filter-feeding zooplankton.

The Importance of Phytoplankton Biomolecule Availability for Secondary Production

The growth and reproduction of animals is affected by their access to resources. In aquatic ecosystems, the availability of essential biomolecules for filter-feeding zooplankton dependents greatly on phytoplankton. Here, we analyzed the biochemical composition, i.e., the fatty acid, sterol and amino acid profiles and concentrations as well as protein, carbon, nitrogen and phosphorus content of 17 phytoplankton monocultures representing the seven most abundant phytoplankton classes in boreal and sub-arctic lakes. To examine how the differences in the biochemical composition between phytoplankton classes affect their nutritional quality for consumers, we assessed the performance of Daphnia, on these diets. Furthermore, we defined the most important biomolecules regulating the somatic growth and reproduction of Daphnia, expecting that higher concentrations of certain biomolecules are needed for reproduction than for growth. Finally, we combined these results with phytoplankton field data from over 900 boreal and sub-arctic lakes in order to estimate whether the somatic growth of Daphnia is sterol-limited when the natural phytoplankton communities are cyanobacteria-dominated. Our analysis shows that Daphnia grows best with phytoplankton rich in sterols, ω-3 fatty acids, protein and amino acids. Their reproduction follows food sterol and ω-3 concentration as well as C:P-ratio being two times higher in Daphnia feeding on cryptophytes than any other diet. Interestingly, we found that a high dietary ω-6 fatty acid concentration decreases both somatic growth and reproduction of Daphnia. When combined with phytoplankton community composition field data, our results indicate that zooplankton is constantly limited by sterols in lakes dominated by cyanobacteria (≥ 40 % of total phytoplankton biomass), and that the absence of cryptophytes can severely hinder zooplankton production in nature.

Variations in the structural and functional diversity of zooplankton over vertical and horizontal environmental gradients en route to the Arctic Ocean through the Fram Strait.

A multi-scale approach was used to evaluate which spatial gradient of environmental variability is the most important in structuring zooplankton diversity in the West Spitsbergen Current (WSC). The WSC is the main conveyor of warm and biologically rich Atlantic water to the Arctic Ocean through the Fram Strait. The data set included 85 stratified vertical zooplankton samples (obtained from depths up to 1000 metres) covering two latitudinal sections (76°30’N and 79°N) located across the multi-path WSC system. The results indicate that the most important environmental variables shaping the zooplankton structural and functional diversity and standing stock variability are those associated with depth, whereas variables acting in the horizontal dimension are of lesser importance. Multivariate analysis of the zooplankton assemblages, together with different univariate descriptors of zooplankton diversity, clearly illustrated the segregation of zooplankton taxa in the vertical plane. The epipelagic zone (upper 200 m) hosted plentiful, Oithona similis-dominated assemblages with a high proportion of filter-feeding zooplankton. Although total zooplankton abundance declined in the mesopelagic zone (200–1000 m), zooplankton assemblages in that zone were more diverse and more evenly distributed, with high contributions from both herbivorous and carnivorous taxa. The vertical distribution of integrated biomass (mg DW m-2) indicated that the total zooplankton biomass in the epipelagic and mesopelagic zones was comparable. Environmental gradients acting in the horizontal plane, such as the ones associated with different ice cover and timing of the spring bloom, were reflected in the latitudinal variability in protist community structure and probably caused differences in succession in the zooplankton community. High abundances of Calanus finmarchicus in the WSC core branch suggest the existence of mechanisms advantageous for higher productivity or/and responsible for physical concentration of zooplankton. Our results indicate that regional hydrography plays a primary role in shaping zooplankton variability in the WSC on the way to the Arctic Ocean, with additional effects caused by biological factors related to seasonality in pelagic ecosystem development, resulting in regional differences in food availability or biological production between the continental slope and the deep ocean regions.

Polychlorinated Biphenyl Bioaccumulation Patterns Among Lake Erie Lower Trophic Level Consumers Reflect Species Ecologies.

Polychlorinated biphenyl (PCB) concentrations were quantified in lower trophic level consumers of the Lake Erie western basin food web to assess the capacity of PCBs to discriminate among trophically similar species inhabiting different compartments of the same ecosystem. Zooplankton were characterized by higher proportions of less chlorinated and hydrophobic homologs relative to zebra mussel (Dreissena polymorpha), mayfly (Hexagenia limbata) and emerald shiner (Notropis atherinoides) samples. PCB biota-sediment accumulation factors (BSAF) differed significantly among species with zebra mussels and emerald shiners having the highest BSAFs. Principal components analysis of sample PCB profiles reflected the contrasting pelagic and benthic habitats occupied by filter-feeding zooplankton and zebra mussel samples. Benthic mayfly PCB profiles were characterized by increasingly hydrophobic (logK OW ≥ 6.9) congeners with more variable emerald shiner profiles reflecting the greater mobility and extent of spatial habitat integration achieved by this secondary consumer. These results contribute to growing evidence for the use of PCBs as ecological tracers in aquatic ecosystems.

Long-term changes of phytoplankton in the lake, not affected by anthropogenic impact (Lake Krivoe, North Karelia)

First studies of the lake ecosystem were performed in 1968–1969 in framework of the International Biological Program, as on a model lake for the observations on the natural dynamic processes. Further work had continued in 1972 and annually from 2002 to 2014. During all study period Cyanobacteria and Chrysophyta have been permanent representatives in phytoplankton. Cyanobacteria were mostly represented by small-cell species from Chroococcales, so their share in the total biomass was low, despite the high abundance. Algae from genera Dinobryon and Uroglena, had dominated in Spring and remained in the plankton during entire season. A distinctive feature of the lake plankton was a low development of diatoms (less than 10% in abundance and biomass) and the absence of the spring outbreak of diatoms in both: under ice and in open water. Cryptomonads (Cryptopyta), which also had been represented throughout of season, became practically new, fairly widespread group in lake phytoplankton. Detailed studies carried out in 2002–2014, have shown that the spring maximum of phytoplankton rarely exceeded the summer one and reached in average 0.46 mg/L. The percentage of each size class of algae in the total biomass of the plankton was determined. Algae with size to 40 microns, which are the most consumed ones by filter feeding zooplankton, constituted a significant share in the Spring time. However the most favorable trophic conditions for zooplankton were during the summer. The development of single-celled Cryptomonad, which reached about 30% of the total biomass, has increased the trophic importance of phytoplankton. Species composition and abundance of phytoplankton in the lake may indicate a conservation of the lake as a clean oligotrophic reservoir.

Algal blooms increase heterotrophy at the base of boreal lake food webs-evidence from fatty acid biomarkers

Physical defenses and grazer avoidance of the bloom-forming microalga Gonyostomum semen may reduce the direct coupling between phytoplankton and higher trophic levels and result in an increased importance of alternative basal food resources such as bacteria and heterotrophic protozoans. To assess the importance of algal and heterotrophic food resources for zooplankton during G. semen blooms and the effects of zooplankton diets on a higher consumer, we analyzed the fatty acid composition of zooplankton and the invertebrate predator Chaoborus flavicans from eight lakes along a gradient in the predominance of G. semen relative to other algae and the duration of G. semen blooms. The proportion of fatty acids of bacterial origin increased significantly along the G. semen gradient in all consumers studied. In addition, the proportion of polyunsaturated fatty acids (PUFA) decreased in cladocerans. These results suggest that heterotrophic pathways can compensate for a reduced trophic coupling between phytoplankton and filter-feeding zooplankton. The lower PUFA content in cladoceran prey from lakes at the higher end of the G. semen gradient did not affect the PUFA content of the predator C. flavicans, suggesting selective assimilation and retention of PUFA and/or feeding on other, more PUFA-rich prey.

Microbial players involved in the decline of filamentous and colonial cyanobacterial blooms with a focus on fungal parasitism.

In the forthcoming decades, it is widely believed that the dominance of colonial and filamentous bloom-forming cyanobacteria (e.g. Microcystis, Planktothrix, Anabaena and Cylindrospermopsis) will increase in freshwater systems as a combined result of anthropogenic nutrient input into freshwater bodies and climate change. While the physicochemical parameters controlling bloom dynamics are well known, the role of biotic factors remains comparatively poorly studied. Morphology and toxicity often - but not always - limit the availability of cyanobacteria to filter feeding zooplankton (e.g. cladocerans). Filamentous and colonial cyanobacteria are widely regarded as trophic dead-ends mostly inedible for zooplankton, but substantial evidence shows that some grazers (e.g. copepods) can bypass this size constraint by breaking down filaments, making the bloom biomass available to other zooplankton species. A wide range of algicidal bacteria (mostly from the Alcaligenes, Flavobacterium/Cytophaga group and Pseudomonas) and viruses (Podoviridae, Siphoviridae and Myoviridae) may also contribute to bloom control, via their lytic activity underpinned by a diverse array of mechanisms. Fungal parasitism by the Chytridiomycota remains the least studied. While each of these biotic factors has traditionally been studied in isolation, emerging research consistently point to complex interwoven interactions between biotic and environmental factors.

Non-microcystin and non-cylindrospermopsin producing cyanobacteria affect the biochemical responses and behavior ofDaphnia magna

Cyanobacterial blooms affect aquatic ecosystems due to their capability of producing cyanotoxins (e.g., microcystins, MC; cylindrospermopsin, CYN) and other bioactive compounds. Filter feeding zooplankton are amongst the first organisms affected and research has mainly focused on their interactions with toxic cyanobacteria. We investigated oxidative stress, biotransformation and energetic responses of Daphnia magna after exposure to cyanobacterial extracts and behavioral changes of the animals exposed to living cells of non-MC and non-CYN producing strains. Enzyme and energetic responses were measured in time kinetic experiments, using extracts of Microcystis botrys, M. wesenbergii, Aphanizomenon aphanizomenoides, Cylindrospermopsis raciborskii, corresponding to 10 mg DW L−1. In behavioral experiments, D. magna was exposed to living cells of Microcystis aeruginosa, A. aphanizomenoides, Dolichospermum circinalis, C. raciborskii, at the density of 400 000 cells mL−1 using a Daphnia toximeter equipment. Despite not producing MC or CYN, some cyanobacterial extracts caused significant increase of biotransformation enzyme, especially catalase, activities from the exposed D. magna after a longer incubation. Total carbohydrates and glycogen contents were increased but the activity of one of the involved enzymes, the malate dehydrogenase, was not changed. Animals' behavior (e.g., swimming, position within water column) was altered in exposures to cultures of C. raciborskii and D. circinalis. These physiological and behavioral alterations indicate stress, which may impair overall performance of zooplankton at the environmental realistic chronic exposure scenario.