Freshwater Cladoceran Research Articles

Intraspecific variation in resource use is not explained by population persistence or seasonality.

Populations of generalist grazers often contain genotypes with "powerful" and "efficient" strategies. Powerful genotypes grow rapidly on rich-quality resources, but slowly on poorer-quality ones, while efficient genotypes grow relatively better on poorer resources but cannot exploit richer resources as well. Via a "power-efficiency" trade-off, variation in resource quality could maintain genetic diversity. To evaluate this mechanism, we sampled six populations of the freshwater cladoceran Daphnia pulicaria. In persisting (year-round) populations, Daphnia consume resources that vary in quality, whereas in non-persisting (spring-only) populations, Daphnia primarily encounter rich-quality resources. We hypothesized that non-persisting populations harbor no efficient clones (hence should show lower growth on poor-quality resources). Although individuals from non-persisting populations remained smaller than individuals from persisting populations, no evidence arose for a trade-off between powerful and efficient strategies. In fact, growth rates on the two diets were positively correlated (instead of negatively, as predicted). Furthermore, in the persisting populations, we predicted that clonal selection from spring to summer should shift the distribution of genotypes from powerful (specialists on richer spring resources) to efficient (poorer, summer resources). Genetic composition of populations shifted from spring to summer, but not toward more efficient genotypes. Therefore, in these lakes, maintenance of variation among genotypes must stem from more complicated factors than population persistence patterns or seasonal shifts in resource quality alone.

Morphological deformation of Daphnia magna embryos caused by prolonged exposure to ibuprofen.

The effect of chronic exposure of freshwater cladoceran Daphnia magna to low, environmentally relevant concentrations i.e 4 μgL−1of ibuprofen (a nonsteroidal anti-inflammatory drug) in a laboratory experiment was studied. We observed the key life history traits of first and fifth generation individuals: age and size at first reproduction, number of first clutch eggs and individual growth rate. Moreover, chosen molecular/subcellular markers of experimental animals stress response such as triglyceride content, heat shock proteins (HSP) expression and DNA:RNA ratio were collected. Overall, chronic exposure to ibuprofen had no significant effect on the molecular markers nor on the life history parameters of the Daphnia. It did, however, caused lethal morphological deformities in embryos and juvenile daphnids. Depending on the clonal affiliation, exposure to a low dosage of ibuprofen over five generations resulted in the deformation of ∼3%–∼10% of the first clutch of offspring. Also, up to 90% of females carried at least one deformed embryo. This is the first time that research has revealed such an effect of ibuprofen on D. magna.

Temperature and clone-dependent effects of microplastics on immunity and life history in Daphnia magna

Microplastic (MP) pollution is potentially a major threat to many aquatic organisms. Yet we currently know very little about the mechanisms responsible for the effects of small MPs on phenotypes, and the extent to which effects of MPs are modified by genetic and environmental factors. Using a multivariate approach, we studied the effects of 500 nm polystyrene microspheres on the life history and immunity of eight clones of the freshwater cladoceran Daphnia magna reared at two temperatures (18 °C/24 °C). MP exposure altered multivariate phenotypes in half of the clones we studied but had no effect on others. In the clones that were affected, individuals exposed to MPs had smaller offspring at both temperatures, and more offspring at high temperature. Differences in response to MP exposure were unrelated to differences in particle uptake, but were instead linked to an upregulation of haemocytes, particularly at high temperature. The clone-specific, context-dependent nature of our results demonstrates the importance of incorporating genetic variation and environmental context into assessments of the impact of plastic particle exposure. Our results identify immunity as an important mechanism underpinning genetically variable responses to MP pollution and may have major implications for predicting consequences of MP pollution.

Biochemical and behavioral effects induced by cocaine exposure to Daphnia magna

Illicit drugs and their metabolites have been identified as emerging aquatic pollutants. Cocaine (COC) is one of the most used illicit drug worldwide. After human consumption, COC enters the aquatic ecosystems, where it is commonly detected in ng L−1 concentration range. Although a number of studies have shown that the exposure to environmental concentrations of COC can induce diverse biochemical, molecular and histological effects on aquatic organisms, the information of COC-induced behavioral alterations is scant. Thus, the present study aimed at exploring both biochemical and behavioral effects induced by the exposure to two environmental concentrations (50 ng L−1 and 500 ng L−1) of COC on the freshwater cladoceran Daphnia magna. Specimens were exposed to selected COC concentrations for 21 days and the effects on the oxidative status, including the amount of reactive oxygen species and the activity of antioxidant (SOD, CAT and GPx) and detoxifying (GST) enzymes, and swimming activity were investigated after 7, 14 and 21 days of treatment, while effects on reproductive success was assessed after 21-days only.. Exposure to COC induced an overproduction of reactive oxygen species and a modulation of the activity of defense enzymes. Moreover, COC affected the swimming behavior and altered the reproductive success of treated specimens. Our results highlighted that environmental concentrations of COC can cause adverse effects at different levels of the biological hierarchy in a zooplanktonic species, confirming the potential threat due to this illicit drug for the aquatic community.

Mesozooplankton and environmental variation during the 2009-2010 ENSO event on the north coast of the Río de la Plata estuary

Previous studies have demonstrated that macro-scale climatic events such as ENSO, cause changes in meteorological and hydrological conditions, inducing physicochemical changes in the water column, as well as in coastal and estuarine communities in the Atlantic Ocean. Rio de la Plata (RdlP) is the second largest estuary of South America, where ENSO is a macro-scale environmental driving force. In this paper, the species composition, abundance, as well as the temporal and horizontal variation of the mesozooplankton in the north coast of the RdlP during 2009-2010 ENSO were analyzed. Zooplankton samples were collected with sub-surface trawls in fifteen stations during eleven sampling surveys. Physico-chemical parameters of the water column (temperature, salinity, dissolved oxygen, turbidity, and chlorophyll a) were determined and related to the RdlP flows. The holoplankton was dominated by estuarine copepod (Acartia tonsa), freshwater cladocerans (Bosmina hagmanni, Ceriodaphnia dubia, Moina sp.), and in the meroplankton, barnacle larvae were the most abundant group. Temporal variability was reflected in abundance differences and ecological indexes between both ENSO phases. The copepods abundance showed a positive association with RdlP flow during El Niño (Nov 2009-Apr 2010), and negative during La Niña-Neutral (Sep 2010-Jan 2011). During El Niño months, the higher richness of typical freshwater cladocerans was observed, promoting a horizontal heterogeneity in the study area. During La Niña-Neutral, the zooplankton showed lower species richness and was dominated by copepods typical of the RdlP (Acartia tonsa). Canonical Correspondence Analysis showed that salinity, RdlP flow, and chlorophyll a explained 88.4% of the total variance of the species-environment relationships. This paper presents new information on zooplanktonic organisms’ response to climatic and hydrological events in the RdlP estuary.

Ecotoxicological assessment of synthetic and biogenic surfactants using freshwater cladoceran species

Surfactants have been continuously detected within aquatic environments as a consequence of their use on a global scale. Lipopeptides are biosurfactants naturally produced by Bacillus subtilis that have been explored as green alternatives. The assessment of ecotoxicological parameters of synthetic and biogenic surfactants are required for evaluating toxicity values and to verify the eco-friendly behaviour of the biological compounds. This study aimed to conduct toxicity testing for different surfactants – sodium dodecyl sulphate and Triton X-100 - and biosurfactants – surfactin, iturin and fengycin - at different concentrations using Daphnia magna as model organism and Dendrocephalus brasiliensis as alternative test species for monitoring of pollutants in tropical freshwaters. According results, both species showed high sensitivity for the anionic compound SDS concerning the recommended dosage use, exhibiting EC50–48h values of 24.1 and 15.4 mg/L for D. magna and D. brasiliensis, respectively. Although the biological source, surfactin showed the lower safety behaviour among the biogenic surfactants, while iturin and fengycin revealed very low toxicity effects on both organisms. Besides, data exhibited a higher responsiveness of D. brasiliensis for all tested compounds in comparison to D. magna, highlighting the importance of this species for monitoring of pollutants in tropical and subtropical environments.

Acute and chronic effects of paracetamol exposure on Daphnia magna: how oxidative effects may modulate responses at distinct levels of organization in a model species.

The modern usage of pharmaceutical drugs has led to a progressive increase in their presence and environment concentrations, particularly in the aquatic compartment which is the most common final dumping location for this specific class of chemicals. These substances, due to their chemical and biological properties, can exert mostly uncharacterized toxic effects to non-target aquatic species, given the diverse pathways they activate, and the large number of putative targets in the wild. Among drugs in the environment, paracetamol assumes a leading role, considering its widespread therapeutic use and consequently, environmental presence. The present study aimed to assess the acute and chronic effects of paracetamol, in ecologically relevant levels, in the freshwater cladoceran Daphnia magna, namely focusing on biochemical and reproductive parameters. Considering the pro-oxidant effects of paracetamol, already described for a large set of aquatic organisms, specific enzymes involved in the anti-oxidant and metabolic responses were quantified, namely catalase (CAT) and glutathione S-transferases (GSTs) activities. Cholinesterases (ChEs) activity was quantified to evaluate the capacity of paracetamol to induce neurotoxicity, an indirect outcome of oxidative effects by paracetamol, that may affect feeding behavior and reproductive outcomes of this crustacean. Paracetamol in the tested levels showed no effect on reproductive traits of D. magna. Results obtained for organisms acutely exposed included significant increases in the activities of both GSTs and CAT, demonstrating a short-term pro-oxidative effect by paracetamol. On the contrary, ChEs activity was significantly decreased in organisms exposed to this drug, showing a possible interference with neurotransmission. On the contrary, no noteworthy effects were reported for organisms chronically exposed to ecologically realistic concentrations, evidencing the transient nature of the obtained biological response. These results demonstrate the responsiveness of D. magna to paracetamol, especially for high levels of exposure that, despite not being environmentally relevant, are able to trigger significant antioxidant responses. No population effects were likely to be caused by realistic levels of paracetamol, and the absence of biochemical changes after chronic exposure suggests that this specific organism may not be deleteriously affected by low levels of paracetamol, under real scenarios of contamination.

Polystyrene nanoplastic exposure induces immobilization, reproduction, and stress defense in the freshwater cladoceran Daphnia pulex

The widespread occurrence and accumulation of plastic waste have been globally recognized as a critical issue. However, there is limited information on the adverse effects of nanoplastics on freshwater invertebrates. In this study, the effects of a polystyrene nanoplastic on physiological changes (e.g., survival, growth, and reproduction) and expression levels of stress defense genes (oxidative stress-mediated and heat shock proteins) in the freshwater flea Daphnia pulex were measured. The results showed that the digestive organs of D. pulex were strongly fluorescent after exposure to the nanoplastic particles, and the 48-h median lethal concentration (LC 50) of the nanoplastic was determined to be 76.69 mg/L. In the 21-day chronic toxicity test, dose- and time-dependent relationships were observed for body length, and the time to first eggs was significantly prolonged in the 0.5 and 1 mg/L groups. The time to clutch was delayed, and total offspring per female and number of clutches were decreased in all the treatment groups. In addition, the offspring per clutch were significantly decreased in the 0.1 mg/L group. As the nanoplastic concentration increased, expression of stress defense genes (SOD, GST, GPx, and CAT) was first induced and then inhibited. The gene expressions of heat shock proteins (HSP70 and HSP90) were induced in all the treatment groups. Our results suggest that nanoplastics can be ingested by the freshwater cladoceran D. pulex and affect its growth and reproduction as well as induce stress defense.

Feeding HUFA and vitamin C-enriched Moina micrura enhances growth and survival of Anabas testudineus (Bloch, 1792) larvae

Better survival and growth of larval stages of fish is the most important objective of any fish hatchery. The present study aimed to assess the effect of feeding a freshwater cladoceran Moina micrura as live food enriched with HUFA, vitamin C or both on survival and growth of climbing perch Anabas testudineus larvae. Three days old larvae were randomly distributed in twelve glass tanks at the rate of 10 larvae per litre of water and fed enriched with HUFA, vitamin C or both and un-enriched M. micrura thrice a day at the rate of 4-5 numbers ml-1 of rearing water for 30 days. Fatty acid analysis of the enrichment emulsions, M. micrura and the larvae was done. The highest survival was observed in larval group fed with HUFA enriched Moina (24 ± 1.53%) and the lowest in the control group (9.3 ± 0.88%). This indicates that enrichment of M. micrura with HUFA alone could enhance the survival rate significantly. Larval group fed with HUFA-Vitamin C enriched M. micrura exhibited significantly (P < 0.05) high body weight gain as well as specific growth rate. Therefore, it was concluded that better survival and growth of larval stages could be achieved by feeding with enriched M. micrura.

ACUTE TOXICITY OF THE ETHANOL EXTRACT AND ETHYL ACETATE FRACTION OF EUPATORIUM FORTUNEI TO DAPHNIA MAGNA

Previous studies have shown that the crude ethanol extract and its ethylacetate fraction of the plant Eupatorium fortunei Turcz strongly inhibited the growth of a harmful freshwater cyanobacterium Microcystis aeruginosa. However, the perspective of using these plant extracts as alternative algicides takes into account their potential risks to other species in aquatic ecosystems, including Daphnia magna. The current study presents the acute toxicity of the extracts to D. magna. The median lethal concentrations, immobilizing 50 % of D. magna, (LC50) after 24 and 48 h of the ethanol extract were 247 and 183 mg L-1, respectively. In the exposure to ethyl acetate fraction, the values of 24h-LC50 and 48h-LC50 were 47 and 13 mg L-1, respectively. The values of dissolved oxygen (DO) and pH in the control and treatments had little change during the 48-hour experiment period, fluctuating from 6.44 ÷ 7.90 and 6.07 ÷ 7.78 mg L-1, respectively, and they were still good conditions for D.magna growth. Finally, these results prove clearly that the ethyl acetate fraction is more toxic to the freshwater cladoceran than the ethanol extract. To our knowledge, it is the first report of the acute toxic estimation of E. fortunei extracts to zooplankton species, D. magna. Chronic toxicity of these extracts to D. magna needs to be studied in next step.

Age-dependent survival, stress defense, and AMPK in Daphnia pulex after short-term exposure to a polystyrene nanoplastic

The widespread occurrence and accumulation of micro- and nanoplastics in aquatic environments has become a growing global concern. Generally, natural aquatic populations are characterized by a variety of multi-structured age groups, for which physiological and biochemical responses typically differ. The freshwater cladoceran, Daphnia pulex, is a model species used extensively in environmental monitoring studies and ecotoxicology testing. Here, the effects of a polystyrene nanoplastic on the physiological changes (i.e., survival) and expression levels of stress defense genes (i.e., those encoding antioxidant-mediated and heat shock proteins) in this freshwater flea were measured. Results from acute bioassays were used to determine the respective nanoplastic LC50 values for five age groups (1-, 4-, 7-, 14- and 21-day-old individuals): the obtained values for the 1- and 21-day-old D. pulex groups were similar (i.e., not significantly different). The expression levels of genes encoding key stress defense enzymes and proteins—SOD, CAT, GST, GPx, HSP70, and HSP90—were influenced by the nanoplastic in all the age groups, but not in the same way for each. Significant differences were observed among all age groups in their expression of the gene encoding the energy-sensing enzyme AMPK (adenosine monophosphate-activated protein kinase) α, β, and γ following exposure to the nanoplastic. Moreover, the expression of AMPK α was significantly increased in the 1-, 7-, and 21-day-old individuals exposed to nanoplastic relative to the control group. Together, these results indicate that age in D. pulex affects the sensitivity of its individuals to pollution from this nanoplastic, primarily via alterations to vital physiological and biochemical processes, such as cellular energy homeostasis and oxidation, which were demonstrated in vivo. We speculate that such age-related effects may extend to other nanoplastics and forms of pollution in D. pulex and perhaps similar marine organisms.

Behavioral responses and starvation survival of Daphnia magna exposed to fluoxetine and propranolol

Fluoxetine and propranolol are neuroactive human pharmaceuticals that occur frequently as pollutants in surface waters. The potential effects of these pharmaceuticals on aquatic organisms have raised concern but many adverse effects are not well characterized for a broad range of concentrations and endpoints. In this study, 6 biological parameters in the freshwater Cladoceran Daphnia magna were compared for their responses to fluoxetine or propranolol exposure: mobility (dichotomous response), active swimming time, swimming distance, swimming velocity, swimming acceleration speed, and survival in the absence of food (starvation-survival). Changes in swimming behavior was quantified by video tracking followed by image analyses at six exposure concentrations between 100 ng/L and 10 mg/L. Active swimming time and swimming distance were the most responsive parameters among the behavioral traits. Sublethal exposure concentrations resulted in nonmonotonic responses and behavior profiling suggested that fluoxetine and propranolol stimulated swimming activity at 1–10 μg/L whereas lower (0.1–1 μg/L) and higher exposure concentrations (>100 μg/L) inhibited swimming activity. The ability to survive in the absence of food when exposed to fluoxetine or propranolol resulted in EC50 and EC10 values that were lower than for swimming behavior (EC50 of 0.79–0.99 mg/L; EC10 of 1.4–2.9 μg/L). Starvation-survival appeared to be a potentially simple and sensitive endpoint for adverse effects in D. magna at intermediate exposure concentrations. Nonmonotonic behavioral responses at low exposure concentrations and decreased ability to survive starvation should be considered in assessment of adverse effects of pharmaceuticals to freshwater invertebrates.

Distinct responses of Copepoda and Cladocera diversity to climatic, environmental, and geographic filters in the La Plata River basin

The distribution of freshwater cladocerans and copepods and the drivers of beta diversity along La Plata basin were studied. We propose that local environmental conditions, dispersal limitation, and climate affect cladocerans and copepods differently owing to their variances in terms of life strategies. We calculated beta diversity using four dissimilarity metrics, and also the relative importance of spatial, environmental, and climatic variables by partitioning variance and forward selection procedure coupled with a partial redundancy analysis. Beta diversity patterns were characterized by a high turnover in the subbasins and a small contribution of nestedness. Forward selection evidenced the influence of total nitrogen and total suspended matter for both copepods and cladocerans, suggesting a strong role of eutrophication in controlling their turnover, but spatial distance, precipitation, and mean temperature of winter were related only to copepods. The last one suggests a likely role of geographic isolation driving speciation and endemism in Copepoda and reinforces the strong effect of climatic variation resulting in the high endemism patterns one finds in the Neotropical region.

Assessment of chemical and physical treatments to selectively kill non-indigenous freshwater zooplankton species

ABSTRACTNon-indigenous zooplankton species pose a biosecurity threat to New Zealand’s freshwater native taxa. Nine species are known to have established in New Zealand lakes to date. The spread of some zooplankton taxa is linked to the translocation of farmed fish, principally grass carp (Ctenopharyngodon idella), and recreational vessel movements. The aims of this study were to assess the effectiveness of a range of chemical and physical treatments for transport water and associated equipment to kill freshwater cladoceran, copepod, and rotifer zooplankton species, and their risk to non-target fish. Sodium chloride was the most effective and applicable chemical treatment tested at length in the cladoceran and, combined with physical treatment via mechanical filtration of water or hot water immersion of equipment (to also manage the risk of diapausing eggs), represents an effective option for the control of non-indigenous zooplankton, with limited impact on stenohaline fish.

Diet Composition and Feeding Habits of Two Engraulid Fish Larvae (Engraulis Japonicus and Coilia Nasus) in the Nakdong River Estuary, Korea

Choi, H.C.; Youn, S.H.; Huh, S.-H., and Park, J.M., 2018. Diet composition and feeding habits of two engraulid fish larvae (Engraulis japonicus and Coilia nasus) in the Nakdong River estuary, Korea. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 346–350. Coconut Creek (Florida), ISSN 0749-0208.Engraulis japonicus and Coilia nasus are members of the family Engraulidae, and their larvae are important components in the estuarian ecosystems that they inhabit. The dietary study of fish larvae is essential to understanding early survival and recruitment in fish populations. This study investigated the dietary compositions and size-related dietary changes in E. japonicus and C. nasus larvae in the Nakdong River estuary. Larvae samples were collected monthly between April and August 2011 using an RN80 net at two stations in the estuary. Gut content analyses revealed that E. japonicus fed mostly on copepods, and secondarily on tintinnids and cladocerans, while C. nasus preferred to consume freshwater cladocerans. These dietary differences between the two larvae were closely related with habitat preference, which provided different local prey sources at each station. As the larvae of both species grew, the consumption of copepods for E. japonicus, and cladocerans for C. nasus, gradually increased, indicating distinct ontogenetic dietary changes. This dietary study of larval E. japonicus and C. nasus is important information for the development of fisheries, and can be implemented in related further studies of areas other than estuaries.

Impact of polystyrene microplastics on Daphnia magna mortality and reproduction in relation to food availability.

Microplastics (MPs) in the environment continue to be a growing area of concern in terms of acute and chronic impacts on aquatic life. Whilst increasing numbers of studies are providing important insights into microparticle behaviour and impacts in the marine environment, a paucity of information exists regarding the freshwater environment. This study focusses on the uptake, retention and the impact of 2 µm polystyrene MPs in the freshwater cladoceran Daphnia magna in relation to food intake (algae Chlorella vulgaris), with MP size chosen to approximately match the cell size of the algae. Daphnia were exposed to varied concentrations of MPs and algae. When exposed to a single concentration of MPs Daphnia almost immediately ate them in large quantities. However, the presence of algae, even at low concentrations, had a significant negative impact on MP uptake that was not in proportion to relative availability. As MP concentrations increased, intake did not if algae were present, even at higher concentrations of MPs. This suggests that Daphnia are selectively avoiding eating plastics. Adult Daphnia exposed to MPs for 21 days showed mortality after seven days of exposure in all treatments compared to the control. However significant differences were all related to algal concentration rather than to MP concentration. This suggests that where ample food is present, MPs have little effect on adults. There was also no impact on their reproduction. The neonate toxicity test confirmed previous results that mortality and reproduction was linked to availability of food rather than MP concentrations. This would make sense in light of our suggestion that Daphnia are selectively avoiding eating microplastics.

Transgenerational effects and recovery of microplastics exposure in model populations of the freshwater cladoceran Daphnia magna Straus

The environmental contamination by microplastics is a global challenge to ecosystem and human health, and the knowledge on the long-term effects of such particles is limited. Thus, the effects of microplastics and post-exposure recovery were investigated over 4 generations (F0, F1, F2, F3) using Daphnia magna as model. Effect criteria were parental mortality, growth, several reproductive parameters, and population growth rate. Microplastics exposure (0.1mg/l of pristine polymer microspheres 1–5μm diameter) caused parental mortality (10–100%), and significantly (p≤0.05) decreased growth, reproduction, and population growth rate leading to the extinction of the microplastics-exposed model population in the F1 generation. Females descending from those exposed to microplastics in F0 and exposed to clean medium presented some recovery but up to the F3 generation they still had significantly (p≤0.05) reduced growth, reproduction, and population growth rate. Overall, these results indicate that D. magna recovery from chronic exposure to microplastics may take several generations, and that the continuous exposure over generations to microplastics may cause population extinction. These findings have implications to aquatic ecosystem functioning and services, and raise concern on the long-term animal and human exposure to microplastics through diverse routes.

Phylogeography of Daphnia magna Straus (Crustacea: Cladocera) in Northern Eurasia: Evidence for a deep longitudinal split between mitochondrial lineages.

Species with a large geographic distributions present a challenge for phylogeographic studies due to logistic difficulties of obtaining adequate sampling. For instance, in most species with a Holarctic distribution, the majority of studies has concentrated on the European or North American part of the distribution, with the Eastern Palearctic region being notably understudied. Here, we study the phylogeography of the freshwater cladoceran Daphnia magna Straus, 1820 (Crustacea: Cladocera), based on partial mitochondrial COI sequences and using specimens from populations spread longitudinally from westernmost Europe to easternmost Asia, with many samples from previously strongly understudied regions in Siberia and Eastern Asia. The results confirm the previously suspected deep split between Eastern and Western mitochondrial haplotype super-clades. We find a narrow contact zone between these two super-clades in the eastern part of Western Siberia, with proven co-occurrence in a single lake in the Novosibirsk region. However, at present there is no evidence suggesting that the two mitochondrial super-clades represent cryptic species. Rather, they may be explained by secondary contact after expansion from different refugia. Interestingly, Central Siberia has previously been found to be an important contact zone also in other cladoceran species, and may thus be a crucial area for understanding the Eurasian phylogeography of freshwater invertebrates. Together, our study provides an unprecedented complete, while still not global, picture of the phylogeography of this important model species.

Acute and Chronic Effects of Three Pharmaceutical Drugs on the Tropical Freshwater Cladoceran Ceriodaphnia silvestrii

Among emerging contaminants, pharmaceuticals are one of the most relevant groups of substances found in aquatic environment, due to their universal use, specific physical-chemical properties, and mode of action in aquatic organisms at low concentrations. Considering the magnitude of concentrations and the considerable small amount of information about their potential ecotoxicological effects on wildlife (especially towards organisms from tropical areas), the present study intended to assess the acute and chronic effects of three pharmaceuticals (the analgesic acetaminophen, the anti-inflammatory diclofenac, and the antihypertensive propranolol) in the tropical crustacean species Ceriodaphnia silvestrii. Results of acute exposures showed a considerable variation in toxicity among pharmaceuticals: acetaminophen (EC50 = 40.3 mg L−1) < diclofenac (EC50 = 37.9 mg L−1) < propranolol (EC50 = 3.17 mg L−1), C. silvestrii being more sensitive to the drug propranolol. Data of chronic toxicity tests showed the occurrence of reproductive adverse effects, but also stimulatory phenomena. Propranolol caused a significant increase in fecundity for the concentrations up to 0.0313 mg L−1, and the rate of population increase was significantly augmented from the lower concentration tested. Considering these results and the wide distribution of C. silvestrii in tropical regions, we suggest the use of this species to be used as test organism in ecotoxicity assays performed in such areas, especially for biomonitoring and/or the determination of effects of pharmaceutical drugs.

Effects of glyphosate formulations on the population dynamics of two freshwater cladoceran species.

The general objective of this work is to experimentally assess the effects of acute glyphosate pollution on two freshwater cladoceran species (Daphnia magna and Ceriodaphnia dubia) and to use this information to predict the population dynamics and the potential for recovery of exposed organisms. Five to six concentrations of four formulations of glyphosate (4-Gly) (Eskoba®, Panzer Gold®, Roundup Ultramax® and Sulfosato Touchdown®) were evaluated in both cladoceran species through acute tests and 15-day recovery tests in order to estimate the population dynamics of microcrustaceans. The endpoints of the recovery test were: survival, growth (number of molts), fecundity, and the intrinsic population growth rate (r). A matrix population model (MPM) was applied to r of the survivor individuals of the acute tests, followed by a Monte Carlo simulation study. Among the 4-Gly tested, Sulfosato Touchdown® was the one that showed higher toxicity, and C. dubia was the most sensitive species. The Monte Carlo simulation study showed an average value of λ always <1 for D. magna, indicating that its populations would not be able to survive under natural environmental conditions after an acute Gly exposure between 0.25 and 35 a.e. mg L-1. The average value of λ for C. dubia was also <1 after exposure to Roundup Ultramax®: 1.30 and 1.20 for 1.21 and 2.5 mg a.e. L-1,respectively. The combined methodology-recovery tests and the later analysis through MPM with a Monte Carlo simulation study-is proposed to integrate key demographic parameters and predict the possible fate of microcrustacean populations after being exposed to acute 4-Gly contamination events.