Cyanobacterial metabolites: Aeruginosin 98A, microginin-FR1, anabaenopeptin-A, cylindrospermopsin and their mixtures affect behavioral and physiological responses of Daphnia magna.

We determined the effects influence of cyanobacterial products metabolites: aeruginosin-A (AER-A), microginin-FR1 (MG-FR1), anabaenopeptin-A (ANA-A), cylindrospermopsin (CYL) and their binary and quadruple mixtures on swimming behavior, heart rate, thoracic limb activity, oxygen consumption and in vivo cell health of Daphnia magna. The study showed that CYL induced mortality of daphnids at the highest concentrations, however three oligopeptides had no lethal effect. All the tested Each single metabolites inhibited swimming speed. The mixtures AER+MG-FR1 and AER-A+ANA-A induced antagonistic and the quadruple mixture synergistic effects. Physiological endpoints were depressed by CYL, however they were simulated by the oligopeptides and their binary mixtures. The quadruple mixture inhibited the physiological parameters with antagonistic interactions between the components were antagonistic. Single CYL, MG-FR1 and ANA-A induced cytotoxicity with synergistic interactions and the metabolites in mixtures showed. The study suggests that swimming behavior and physiological parameters may be affected by single cyanobacterial oligopeptides, however their mixtures may induce different total effects.

Effects of cyanobacterial metabolites: Aeruginosin 98A, microginin-FR1, anabaenopeptin-A, cylindrospermopsin in binary and quadruple mixtures on the survival and oxidative stress biomarkers of Daphnia magna.

The aim of our study was to determine the effects of aeruginosin 98 A (ARE-A), microginin-FR1 (MG-FR1), anabaenopeptin-A (ANA-A) cylindrospermopsin (CYL) and their binary and quadruple mixtures on the survival and the levels of oxidative stress biomarkers in Daphnia magna: total glutathione (GSH), catalase (CAT), dismutase (SOD) and malondialdehyde (MDA). The biochemical indicators were measured with ELISA kits and the interactive effects were determined by isobole and polygonal analysis with Compusyn® computer software. The study revealed that oligopeptides did not decrease daphnid survival, only CYL inhibited this parameter, with synergistic effects when it was used as a component. The single metabolites at the two highest concentrations and all the binary and quadruple mixtures at all concentrations diminished GSH level, however both in the binary and in the quadruple mixtures most of the interactions between the metabolites were antagonistic. Nearly additive effects were found only in AER-A + CYL and MG-FR1+CYL. On the other hand, CAT activity was slightly increased in daphnids exposed to the binary mixtures with antagonistic interactions, however nearly addivive effects were found in animals exposed to the mixture of AER-A + ANA-A and synergistic in the quadruple mixture. SOD was elevated in daphnids exposed to single AER-A and MG-FR1, however it was diminished in the animals exposed to ANA-A and CYL. Binary mixtures in which CYL was present as a component decreased the level of this enzyme with nearly additive interactions in ANA-A + CYL. The quadruple mixture increased SOD level, with antagonistic interactions. Both single cyanobacterial metabolites, their binary and quadruple mixtures induced lipid peroxidation measured by MDA level and most of interactions in the binary mixtures were synergistic. The study suggested that antioxidative system of Daphnia magna responded to the tested metabolites and the real exposure to mixtures of these products may lead to various interactive effects with varied total toxicity.

Environmentally realistic concentrations of ibuprofen influence life histories but not population dynamics of Daphnia magna.

Ibuprofen is a nonsteroidal anti-inflammatory drug that can be found in freshwater ecosystems. Due to its current presence in aquatic ecosystems, this pharmaceutical has aroused concerns about its impact on aquatic biota. As a result, ibuprofen is the one of the most frequently studied pharmaceuticals. However, most of these studies focus on short-term observations of biomarkers and physiological endpoints. This paper presents the outcomes of whole-life-cycle observations and six-month observations of the population dynamics of Daphnia magna reared under the influence of 1 µg/L, 2 µg/L and 4 µg/L of ibuprofen. Individuals reared under the influence of ibuprofen grew slowly, matured later and lived longer. Moreover, they displayed a higher reproduction rate and carried smaller broods but delivered larger neonates. Ibuprofen in concentrations of 1 µg/L and 2 µg/L had the most significant effect on the above traits. The observed impact of ibuprofen at the individual level did not transfer to population size and dynamics. All the populations represented a typical boom and bust cycle with restricted reproduction during the periods of highest population size. This is the first study to explore the linkage between the life histories of aquatic invertebrates and the actual response of their populations to the occurrence of ibuprofen in the environment. The study emphasizes the need to apply the protocol of whole life-cycle observation in tandem with population scrutiny, since such a protocol can reveal the virtual responses of aquatic biota to the presence of chemicals in the environment.

Behavioral disturbances induced by cyanobacterial oligopeptides microginin-FR1, anabaenopeptin-A and microcystin-LR are associated with neuromotoric and cytotoxic changes in Brachionus calyciflorus.

Aquatic animals are exposed to various cyanobacterial products released concomitantly to the environment by decaying blooms. Although there exist results on the toxicity of cyanobacterial extracts little is known on the influence of pure oligopeptides or their mixtures and elucidated mechanisms of behavioral toxicity in zooplanktonic organisms. Therefore, the aim of the present study was to assess the effects of single and mixed pure cyanobacterial oligopeptides: microginin FR-1 (MG-FR1), anabaenopeptin-A (ANA-A) and microcystin-LR (MC-LR) at various concentrations on the swimming behavior and catecholamine neurotransmitter activity, muscular F-actin structure, DNA nuclear content and cell viability of a model rotifer Brachionus calyciflorus. Swimming behavior was analyzed with the use of video digital analysis. Fluorescent microscopy imaging was used to analyze neuromotoric biomarkers in the whole organisms: neuromediator release (by staining with EC517 probe), muscle F-actin filaments (by staining with blue phalloidin dye). DNA content and cytotoxicity was also determined by Hoechst 34580 and propidium iodide double staining, respectively. The results showed that single oligopeptides inhibited all the tested endpoints. The binary mixtures induced synergistic interaction on swimming speed except for MG-FR1 +MC-LR which was nearly additive. Both binary and ternary mixtures also synergistically degraded F-actin and triggered cytotoxic effects visible in the whole organisms. Antagonistic inhibitory effects of all the binary mixtures were found on catecholamine neurotransmitter activity, however the ternary mixture induced additive toxicity. Antagonistic effects of both binary and ternary mixtures were also noted on nuclear DNA content. The results of the study suggest that both depression of neurotransmission and impairment of muscle F-actin structure in muscles may contribute to mechanisms of Brachionus swimming speed inhibition by the tested single cyanobacterial oligopeptides and their mixtures. The study also showed that natural exposure of rotifers to mixtures of these cyanobacterial metabolites may result in different level of interactive toxicity with antagonistic, additive synergistic effects depending on the variants and concentrations present in the environment.

Do experimental conditions bias plankton responses to increased concentration of dissolved organic matter (DOM)? A meta-analytical synthesis of the published results.

The concentration of dissolved organic matter (DOM) in aquatic ecosystems has manifold direct and indirect consequences for primary and secondary production. Theoretical approaches suggest a negative effect of DOM on phytoplankton and a positive effect on bacteria, both of which alter the development of metazooplankton, the main consumer of bacteria and phytoplankton. However, experimental observations give heterogeneous results on the effect sizes of plankton in relation to DOM addition. Here, the synthesis of 411 effect sizes of plankton in response to DOM is presented from 59 studies. The referenced studies display effect sizes in relation to various DOM sources and different experimental designs. Thus, the hypothesis that neither DOM quality nor the type of experiment bias the effect size response of plankton was tested; the hypothesis was tested separately for bacterioplankton, phytoplankton and metazooplankton with the use of a meta-analytical approach. DOM quality was represented by the five different sources of DOM that are used most often in these experiments, i.e., natural water, bog leachate, glucose/sucrose, terrestrial plant leachate, and soil leachate. The experiment types comprised in situ experiments, i.e., experiments taking place under manipulated conditions in a natural ecosystem, and ex situ experiments, i.e., those taking place outside of a natural ecosystem. The meta-analyses showed that, although total DOM had a positive influence on the effect size of bacterioplankton and an insignificant influence on metazooplankton, the effect sizes differed significantly in relation to DOM source and the type of experiment. The effect size of phytoplankton, although not significantly related with total DOM, differed in response to DOM source but not experiment type. The results suggest that experimental conditions may produce artifacts in the strength of responses of aquatic biota to DOM concentrations.

Food resource partitioning between juvenile and mature weatherfish Misgurnus fossilis.

This study represents a description of the diet composition of one of the largest European cobitids, the weatherfish Misgurnus fossilis. Specimens were collected in a drainage canal, representing a typical habitat for weatherfish, and with gut content analysis conducted with regard to individual total length and maturity stage. Overall, the weatherfish diet mainly consisted of Copepoda, Cladocera, Ostracoda, Oligochaeta, Asellus aquaticus, Chironomidae and Coleoptera larvae, Gastropoda, and detritus. To evaluate size-related patterns of resource use, fish were assigned to two size classes, defined according to size at first maturation. ANOSIM analyses revealed major ontogenetic shifts in feeding strategy, which were related to size and maturity, with a significant ontogenetic shift in feeding pattern, marked by differences in the proportions of the main taxonomic groups of prey consumed. Copepoda and Cladocera dominated in the diet of small and immature individuals, while large weatherfish primarily fed on detritus. Similarly, cluster analysis of diet classified into these food types showed distinct two groups comprising juvenile and mature fish. The weatherfish is a food opportunist using all available resources, but spatially showed a change in feeding sites. Smaller and sexually immature individuals more often use prey caught in the water column and among macrophytes, while larger (sexually mature) individuals occupying the bottom, much more often use detritus as a food base.

Population dynamics and life history traits of Daphnia magna across thermal regimes of environments.

The consequences of raising temperatures have been intensively studied by biologists and ecologists for the past few decades. However, current climatic changes also include many anomalous weather events, such as intra-seasonal heatwaves followed by immediate decreases in temperature. In this study, the responses of population development and life history traits to different thermal regimes were investigated. The freshwater water flea Daphnia magna (Cladocera, Crustacea) was used as a model organism. Daphnia magna populations were monitored under temperature regimes of warm (25 °C), cold (5 °C), synchronous (gradual changes between 25 °C and 5 °C) or stochastic (random changes between 25 °C and 5 °C). Population size of D. magna populations decreased with unpredictability of thermal conditions; the highest density of D. magna was found in the warm environment and the lowest density in the stochastic environment. Thermal regime had significant impact on the prevalence of asexual and sexual reproduction of D. magna. Under a synchronous regime, an accumulation of asexual reproduction was observed during cold episodes; this was followed by a phase of population disturbance, manifesting itself in high fluctuations of asexual reproduction and a pattern of sexual reproduction typical of a cold regime. Under a stochastic regime, the population disturbances were observed throughout the duration of the experiment. Daily observations of individual life history traits revealed that the development of populations under different thermal regimes resulted from the regime-specific survivability of neonates. Population development was also affected by the frequency of reproduction, which consisted of the number of broods carried per lifetime. The results indicate that not only temperature but also shifts in thermal conditions have an important influence on individual life history traits and population dynamics of D. magna. It is important to consider the effects of shifts in water temperature on demographic and individual traits simultaneously because the impact of thermal changes on population traits can be modified by individual life histories.

Ciliates as restoration indicators in peatbogs - 10 years of study.

There is almost no information on how restoration of Sphagnum-dominated peatbogs, and in particular removal of reeds, affects the functioning of ciliate communities. Changes in vegetation patterns caused by restoration procedures may take years to be observed, while microbial processes already display effects after short-term exposure to changes in environmental conditions due to restoration. Based on the results of a long-term study, we assumed that mowing down of reeds causes changes in the physicochemical properties of peatbog water and sought to answer the question of how ciliate communities react to these changes and whether these microorganisms can play a significant role as bioindicators in evaluating the restoration process. Removal of reeds clearly modified the taxonomic composition and abundance of ciliates. This was reflected in an increase in the abundance and diversity of these protozoa and in a significant increase in the proportion of sphagnophilous species. Our results suggest an indicator species approach based on functional groups may be appropriate for biomonitoring peatbog restoration. A better understanding of what regulates microbial populations and activity in peatbogs and unravelling of these fundamental mechanisms are particularly critical in order to more accurately predict how peatbogs will respond to anthropogenic disturbances.

Effects of experimental addition of nitrogen and phosphorus on microbial and metazoan communities in a peatbog.

Interactions between microbial communities and the classical grazing food chain are essential for understanding the functioning of peatbog ecosystems. However, little is known of how short-term intensification of eutrophication processes may influence microbial and metazoan communities in transitional peatbog. We addressed the hypothesis that an increase in the concentration of nutrients will affect the species richness and abundance of microorganisms and small metazoans and cause changes in the food web structure in a peatbog. The experiments were performed in a transitional peatbog. Four experimental variants were conducted (control and nutrient-enriched: +P, +N and P+N). Increased habitat fertility was found to modify the taxonomic composition and functioning of microbial communities. We observed a strong reduction in the species richness of testate amoebae-top predators, and a substantial increase in the abundance of bacteria, flagellates and ciliates. A better understanding of which parameters regulate microbial populations in peatbogs is critical for more accurate prediction of how peatbogs will respond to global climate change or anthropogenic disturbances.

Different levels of precision in studies on the alimentary tract content of omnivorous fish affect predictions of their food niche and competitive interactions.

The food niche partitioning of omnivorous fish is commonly estimated on the basis of the alimentary tract content (ATC). However, since omnivorous fish utilise different ecological formations, data relating to ATC are very noisy, since an identified ATC comprises remains that can be determined according to the species level, determined only according to general food categories (i.e. higher taxonomic levels) as well as amounts of fragmented and digested remains that cannot be determined taxonomically. Thus, a variety of scales of precision can be applied during work on ATC. Up until now, there has been no evidence as to whether and how precision in ATC estimation can affect the results. This study aims at assessing how three different options of the same database influence the effectiveness and concurrency of indexes commonly used to describe the food niche of fish. The options include: (1) only general (higher than species level) food categories; (2) categories of different levels of generality; and (3) only detailed (species level) food categories. The study shows that the use of detailed (species level) food categories only, with the exclusion of general food categories, is the best method to recognise food niche partitioning and competitive interactions among fish. The food categories estimated in detail were cladocerans, and the possibility to use cladocerans as specific markers to find similarities in fish diets is discussed.

Spatial distribution of brood-bearing females of limnetic species of Cladocera.

In this study, the spatial distribution of brood-bearing females of five species of limnetic cladocerans (Daphnia cucullata, D. longispina, Bosmina coregoni, B. longirostris, Diaphanosoma brachyurum) in the deep mesotrophic lake in relation to the predation pressure of planktivorous fish (roach Rutilus rutilus, perch Perca fluviatilis, catfish Ictalurus nebulosus, white fish Coregonus albula, bleak Alburnus alburnus), and planktonic invertebrates (cyclopoids Mesocyclops leuckartii, Thermocyclops oithonoides, T. crassus, and cladoceran Leptodora kindtii) as well as some environmental variables was estimated. Most cladocerans showed apparent differences in horizontal distribution (ANOVA F=0.2-0.45, P<0.05) in the littoral zone and lack of such differences in the pelagic zone (F=0.07-0.13, P>0.05). Vertical distribution of most species, in turn, showed a clear pattern in the pelagic zone (F=0.31-0.39, P<0.05) and less regularities in the littoral zone (F=0.15-029, P>0.05). The differences in spatial distribution of non-predated and predated species suggest that predation pressure, but not predatory type, was an important factor structuring their distribution. Other factors that affected their distribution were conductivity, dissolved oxygen, TOC and macrophyte biomass; however, most of those variables better explained the distribution of brood-bearing cladocerans in the vertical than horizontal aspect.