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The toxicity of the insecticide chlorantraniliprole and its formulated product Altacor® was determined for the Cladoceran, Ceriodaphnia dubia Richard. Acute toxicity (48 h) and 21 d population studies were conducted. The hypothesis of this study was that these two compounds would have different toxicities. We conducted acute and chronic toxicity studies for each compound and compared the results to test this hypothesis. 48 h LC50s (95% CL) for chlorantraniliprole and Altacor® were 8.5 (6.6–11.5) and 6.0 (3.7-9.0) µg chlorantraniliprole/L water, respectively. Therefore, chlorantraniliprole and Altacor® were equitoxic to C. dubia at LC50 based on overlap of the 95% CL. In the population study, chlorantraniliprole and Altacor® concentrations equivalent to the acute LC5, 10, 25, and 50 for each product were evaluated on populations of C. dubia. Number of individuals after 21 d was the endpoint evaluated. T-tests conducted at each LC value indicated that there was no significant difference in population size between these two products at each LC value evaluated. Previous studies show that toxicity can vary greatly between formulated and technical grade pesticides. However, our results show that chlorantraniliprole and its formulated product, Altacor® were equally toxic to C. dubia. Therefore, making assumptions about the toxicity of formulated and unformulated products is ill advised.

Experiments in microcosms have demonstrated that beaver vital activity products (BVAPs) promote an increase in concentrations of total nitrogen (N) and total phosphorus (P), a decrease in the N/P value in water, and an increase in the abundance and biomass of bacterioplankton. Under such conditions, the abundance and biomass of small Ceriodaphnia dubia Richard and large Daphnia (Ctenodaphnia) magna Straus, which live separately, increase. The coexistence of these cladocerans in microcosms under the BVAP influences results in a high increase in the abundance and biomass of D. magna ; in similar experiments without the influence of BVAP, Ceriodaphnia dubia becomes more abundant. The results of bioassay demonstrate that the number of newborns of Ceriodaphnia dubia decreases in water where Daphnia magna is numerous owing to BVAPs. It is suggested that the vital activity products of large representatives of the genus Daphnia inhibit the fecundity of small species of Cladocera. This fact, along with the high competitiveness of large cladoceran species under conditions of a high level of nutritive base, determine the formation of zooplankton communities in beaver ponds which are characterized by a high abundance and biomass and low uniformity

Antiviral drugs are a class of medications used for treating viral infections. Due to their widespread use, especially in cases of pandemics and limited human metabolism, antivirals have been detected in multiple environmental matrices. This study aims to evaluate the chronic effects of acyclovir, efavirenz, lamivudine and zidovudine using Ceriodaphnia dubia and Raphidocelis subcapitata. The results with R. subcapitata showed the following toxicities: zidovudine (IC50 = 5.442 mg L−1) < acyclovir (IC50 = 3.612 mg L−1) < lamivudine (IC50 = 3.013 mg L−1) < efavirenz (IC50 = 0.034 mg L−1). The results of the chronic bioassay with C. dubia demonstrated that zidovudine is the least toxic (EC50 = 5.671 mg L−1), followed by acyclovir (EC50 = 3.062 mg L−1), lamivudine (EC50 = 1.345 mg L−1) and efavirenz (EC50 = 0.026 mg L−1). Both species have been shown to be sensitive to efavirenz. A risk quotient (RQ) was calculated, and efavirenz had an RQ greater than 1 for both species, and lamivudine had an RQ greater than 1 for C. dubia, representing a high ecological risk for these organisms. Antivirals pose a significant environmental risk to aquatic organisms and should be taken into consideration in future monitoring of water sources.

* Micro-plastics (MPs) significantly increase Pb toxicity. * Algae reduce the combined toxicity of MP and Pb. * The toxicity increase comes from high soluble Pb and MP-Pb uptake. * The toxicity reduction might come from energy related pathway. Microplastics (MPs) have been recognized as a new class of emerging contaminants in recent years. They not only directly impact aquatic organisms, but also indirectly impact these organisms by interacting with background toxins in the environment. Moreover, under realistic environmental conditions, algae, a natural food for aquatic organisms, may alter the toxicity pattern related to MPs. In this research, we first examined the toxicity of MPs alone, and their effect on the toxicity of lead (Pb) on Ceriodaphnia dubia ( C. dubia), a model aquatic organism for toxicity survey. Then, we investigated the effect of algae on the combined toxicity of MPs and Pb. We observed that, MPs significantly increased Pb toxicity, which was related to the increase in soluble Pb concentration and the intake of Pb-loaded MPs, both of which increased the accumulation of Pb in C. dubia. The presence of algae mitigated the combined toxicity of MPs and Pb, although algae alone increased Pb accumulation. Therefore, the toxicity mitigation through algae uptake came from mechanisms other than Pb accumulation, which will need further investigation.

Genetic variation in parasites has important consequences for host–parasite interactions. Prior studies of the ecologically important parasite Metschnikowia bicuspidata have suggested low genetic variation in the species. Here, we collected M. bicuspidata from two host species (Daphnia dentifera and Ceriodaphnia dubia) and two regions (Michigan and Indiana, USA). Within a lake, outbreaks tended to occur in one host species but not the other. Using microsatellite markers, we identified six parasite genotypes grouped within three distinct clades, one of which was rare. Of the two main clades, one was generally associated with D. dentifera, with lakes in both regions containing a single genotype. The other M. bicuspidata clade was mainly associated with C. dubia, with a different genotype dominating in each region. Despite these associations, both D. dentifera- and C. dubia-associated genotypes were found infecting both hosts in lakes. However, in lab experiments, the D. dentifera-associated genotype infected both D. dentifera and C. dubia, but the C. dubia-associated genotype, which had spores that were approximately 30% smaller, did not infect D. dentifera. We hypothesize that variation in spore size might help explain patterns of cross-species transmission. Future studies exploring the causes and consequences of variation in spore size may help explain patterns of infection and the maintenance of genotypic diversity in this ecologically important system.

This study aimed to assess the quality of water and sediment of urban streams located in Santa Cruz do Sul County, RS, Brazil, using the microcrustacean Ceriodaphnia dubia as test-organism. Quarterly scientific excursions to the streams were held on August and November 2011, February and May of 2012 in order to collect water and sediment samples, in the upper reaches and lower reaches, totalizing 8 points. To evaluate the toxicity, the microcrustacean C. dubia was used. The results indicated high toxicity levels detected in samples P2, P6 and P8, as they caused the mortality of 100% of organisms in the water samples and sediment samples, denoting acute effect. Yet, all upstream sites showed chronic effects in sediment samples, at least for one collection period, with the highest significant toxicity level among all samples, which indicates the presence of contamination even in upper areas.

Metal oxides comprise a large group of chemicals used in water treatment to adsorb organic pollutants. The ability of titanium dioxide (TiO2) and iron (III) oxide (Fe2O3) to reduce the chronic toxicity of (phenolic) C6H6(OH)2 isomers, namely hydroquinone (HQ) and catechol (CAT) to Ceriodaphnia dubia and Pimephales promelas (less than 24 h-old) were investigated. The toxic endpoints following metal oxide treatment were compared to endpoints of untreated CAT and HQ. In chronic toxicity testing, HQ resulted in greater toxicity than CAT for both test organisms; the median lethal concentrations (LC50) for CAT were 3.66 to 12.36 mg.L−1 for C. dubia and P. promelas, respectively, while LC50 for HQ were 0.07 to 0.05 mg.L−1, respectively. Although both treated solutions presented lower toxic endpoints than those in the untreated solutions, Fe2O3 had a better potential to reduce the toxic effects of CAT and HQ than TiO2.

The Salinas Valley in Monterey County, California, USA, is a highly productive agricultural region. Irrigation runoff containing pesticides at concentrations toxic to aquatic organisms poses a threat to aquatic ecosystems within local watersheds. This study monitored the effectiveness of a constructed wetland treatment system with a granulated activated carbon (GAC) filter installation at reducing pesticide concentrations and associated toxicity to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus. The wetland was supplied with water pumped from an impaired agricultural and urban drainage. Across five monitoring trials, the integrated system’s average pesticide concentration reduction was 52%. The wetland channel and GAC filtration components individually provided significant treatment, and within each, pesticide solubility had a significant effect on changes in pesticide concentrations. The integrated treatment system also reduced nitrate by 61%, phosphate by 73%, and turbidity by 90%. Input water was significantly toxic to C. dubia and H. azteca in the first trial. Toxicity to C. dubia persisted throughout the system, whereas toxicity to H. azteca was removed by the channel, but there was residual toxicity post-GAC. The final trial had significant input toxicity to H. azteca and C. dilutus. The channel reduced toxicity to H. azteca and removed toxicity to C. dilutus. GAC filtration reduced H. azteca toxicity to an insignificant level. There was no input toxicity in the other three trials. The results demonstrate that a wetland treatment system coupled with GAC filtration can reduce pesticide concentrations, nutrients, suspended particles, and aquatic toxicity associated with agricultural runoff.

Aquatic pollution caused by dyes has increased together with the growth of activities using colorants such as the textile, leather, food, and agrochemicals industries. Because most popular azo dyes are synthesized from benzidine, a carcinogenic compound, a threat to aquatic biota could be expected. The use of single species for toxicity assessment provides limited data, so a battery of test organisms, including representatives of different trophic levels such as algae, zooplankters, and fish, could undoubtedly provide more information. Therefore, our study was aimed at evaluating the toxic effect of the azo dye Direct blue 15 (DB15) on a battery of bioassays using a primary producer (Pseudokirchneriella subcapitata), a primary consumer (Ceriodaphnia dubia), and a secondary consumer (Danio rerio). P. subcapitata was more sensitive to DB15 (IC50 = 15.99 mg L−1) than C. dubia (LC50: 450 mg L−1). In the algae exposed to DB15, chlorophyll-a and -b were significantly increased, and carotenoids were reduced. The concentrations of protein, carbohydrates, and lipids per cell in P. subcapitata exposed to all DB15 concentrations were significantly higher than that measured in control. At 25 mg L−1 of DB15, survival, total progeny, and the number of released clutches were significantly decreased, and the start of reproduction was delayed in C. dubia. DB15 did not induce lethal or sublethal effects in D. rerio embryos at any of the tested concentrations from 24 to 72 h post-fertilization (hpf), but from 96 to 144 hpf, the larvae exposed to 100 and 500 mg L−1 developed yolk sac edema, curved tail, and skeletal deformations. After 144 hpf, DB15 produced a significant increase in embryos without a heartbeat, as the concentration of dye raised. The textile-used, azo dye DB15, caused toxic effects of different magnitude on microalgae, cladocerans, and zebrafish embryos; for this reason, the discharge of this colorant into waterbodies should be regulated to prevent environmental impacts.

Aquatic organisms are subject to various forcing factors that affect their structure, some of which are natural, while others result from human activities, both having variable effects. This study aimed to determine the importance of a natural stressor (zooplankton) and an herbicide (atrazine) on phytoplankton density and morphological composition in a microcosm experiment. A natural phytoplankton assemblage was exposed to two zooplankton predators: a copepod (Argyrodiaptomus falcifer) and a cladoceran (Ceriodaphnia dubia), and to atrazine (27 µg L−1), in three combinations of factors (zooplankton treatments (Z), atrazine treatment (A), the combination of both (ZA)) plus a Control. The experiment lasted 48 h. Samples were taken at the beginning and the end of the experiment, and relevant limnological variables, including inorganic nutrient concentrations, were considered. Results indicated differences in phytoplankton densities when treatments were compared with Control. In this respect, Chlorophyceae, Euglenophyceae, and Bacillariophyceae exhibited more changes than other phytoplankton classes. Chlorophyceae densities tended to be higher in the Control than in the treatments; the combination of zooplankton and atrazine favored Euglenophyceae, while atrazine favored Bacillariophyceae densities. Regarding morphological groups, unicellular and small colonies (<35 µm), showed differences between the Control and particularly with Z treatment, colonial-cenobia forms were negatively affected by atrazine and silica forms were favored by both stressors combined. It is concluded that interactions among natural and anthropogenic stressors could be complex, influencing factors such as phytoplankton taxonomical affinities, morphological groups, and the nature of the stressor applied.