Effectiveness of a Constructed Wetland with Carbon Filtration in Reducing Pesticides Associated with Agricultural Runoff

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.

Effect-based water quality assessment of rivers receiving discharges from legacy mines by using acute and chronic bioassays with two cladoceran species

Information about the ecotoxicological impacts of surface waters that receive discharges from legacy mines is valuable to infer the ecological impacts on natural environment for managing mine discharges. In this study, we investigated behavioural and reproductive responses of two cladoceran species Ceriodaphnia dubia and Daphnia magna to water samples collected from metal-contaminated and reference rivers near legacy mines in Japan. The toxicity identification evaluation (TIE) of water samples that caused D. magna immobility was conducted to evaluate the key metals causing acute toxicity. The results of our water quality assessment performed using two cladoceran species demonstrated modest to significant adverse effects on their behaviour and reproduction, suggesting the potential for ecotoxicological impacts on natural populations and communities at several contaminated sites that received mine drainage. The results of TIE of water samples that caused D. magna immobility indicated likely contributions of Zn and Cu. These results imply that effect-based water quality assessments such as ours can provide direct and unique evidence of the ecotoxicological impacts of metals in river waters, which will be useful for better understanding and predicting the ecological effects of these metals in the natural environment.

Chronic toxicity and environmental risk assessment of antivirals in Ceriodaphnia dubia and Raphidocelis subcapitata

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. HIGHLIGHT Evaluation of the ecotoxicity of acyclovir, efavirenz, lamivudine and zidovudine. The most toxic antiviral for Ceriodaphnia dubia and Raphidocelis subcapitata was efavirenz. Results suggest potential risk to environmental and public health.

Desenvolvimento populacional de duas espécies de cladóceros alimentados com microalgas cultivadas em laboratório

O presente estudo avalia o efeito da dieta sobre a reprodução e o desenvolvimento dos cladóceros Ceriodaphnia dubia e Simocephalus iheringi, cultivados em laboratório. Indivíduos adultos foram distribuídos por seis frascos de 1 L (10 indivíduos por frasco), divididos em dois lotes iguais. Um lote foi tratado com dieta mista de microalgas (Ankistrodesmus sp., Dictyosphaerium sp. e Volvox sp.) cultivadas em laboratório e o outro lote foi tratado com dieta unialgal (Volvox sp.). O período experimental foi de 21 dias, com fotoperíodo de 8 h e temperatura entre 26 e 28 ºC. A quantidade fornecida foi de 20 mL da cultura algal com a densidade de 1,01 x 106 células mL-1, a cada quatro dias. Foram feitas duas contagens da população (sete e 14 dias), em câmara de Sedgwick-Rafter, com aumento de 40 X, utilizando-se subamostras de 1 mL. Para cada tratamento foi verificada a fecundidade média, o tempo de desenvolvimento embrionário, o tempo de desenvolvimento pós-embrionário, a idade da primeira reprodução (IPR), o tempo de vida (TV), a taxa intrínseca de crescimento e o tempo de duplicação da população. Para as duas espécies estudadas, a fecundidade média e o crescimento populacional foram maiores, com a dieta mista. Esta proporcionou maior tempo de vida para Ceridaphnia dubia e menor tempo de vida para Simocephalus iheringi, em relação à dieta unialgal. A fecundidade foi afetada pela dieta, pelo tamanho das fêmeas (Ceridaphnia dubia) e pelo tamanho da população (Simocephalus iheringi). Os melhores resultados, para ambas as espécies, foram obtidos com a dieta mista.

A Tale of Two Metrics: The EPA Risk Quotient Approach versus the Delay in Population Growth Index for Determination of Pesticide Risk to Aquatic Species

The risk that two closely related insecticides, spinetoram and spinosad, posed to three Cladoceran species, Ceriodaphnia dubia, Daphnia pulex, and D. magna was determined using two approaches, the USEPA Risk Quotient method and the Delay in Population Growth Index (DPGI). Results of the RQ method showed that spinetoram posed a risk to all three species, but spinosad posed a risk only to C. dubia. The DPGI analysis showed that exposure to spinetoram resulted in populations of all three species being delayed > 3 generation times. Exposure to the LC50 and the lower 95% CL resulted in delayed populations while exposure to the upper 95% CL concentration of spinetoram resulted in no recovery of any of the three species over the course of the modeling exercise (88 d). Exposure to the lower and upper 95% Cl and the LC50 of spinosad resulted in C. dubia populations being delayed > 3 generations. D. pulex populations were not negatively affected after exposure to spinosad. D. magna populations were delayed > 3 generations, but only after exposure to the upper 95% Cl of spinosad. These results illustrate that although the EPA risk quotient method indicated that spinetoram posed a risk to all three species and that spinosad only posed a risk to C. dubia, the DPGI showed that D. magna would be negatively affected by spinosad and none of the three species would recover after exposure to the upper 95% CL of spinetoram. Because the DPGI uses the 95% Cl as well as the LC50 in its calculation and produces a measure of population growth and recovery or lack thereof, it provides more detailed information in terms of the potential risk of pesticides to populations than the RQ method.

Mutagenic and ecotoxicological assessment of urban surface runoff flowing to the beaches of Guarujá, State of São Paulo, Brazil

Along the coast of the State of São Paulo, Brazil, urban channels introduce a complex mixture of pollutants into the South Atlantic Ocean, that may cause deleterious effects to the aquatic biota. The objective of this study was to analyse, for the first time, the mutagenicity (Ames Salmonella/microsome test) and ecotoxicity (acute and chronic tests, with Daphnia simillis and Ceriodaphnia dubia, respectively) exerted by the diffuse loads discharged in Guarujá, São Paulo coast, Brazil. Water sampling occurred bimonthly between January and July 2018 (rainy season: January through March; dry season: May through July) at four beaches with different profiles of land use and occupation: Tombo (Blue Flag certification), Enseada (high use by tourists), Perequê (fishing community), and Iporanga (conservation unit). No mutagenic potential was detected in the complex mixtures flowing to the study beaches. However, 30 and 80% of the analyses showed acute and chronic toxicities, respectively, mainly in Enseada and Perequê channels during the rainy season. To improve the environmental quality of these coastal waters and to reduce the ecological risks posed to the aquatic organisms and public health, several actions are imperative, such as the amelioration of the basic sanitation facilities and land regularisation actions of these beaches.

Chronic toxicity of three neonicotinoid insecticides and their mixture on two daphniid species: Daphnia magna and Ceriodaphnia dubia

Neonicotinoid insecticides represent nearly a quarter of the global market and are widely used in agriculture but also for lawn, garden care, and pest control. They are highly water-soluble, persistent in soil, and may enter the aquatic compartment via spray drift, runoff, or leaching, and contribute to downstream aquatic toxicity. Although insects appear to be the most sensitive group to neonicotinoids, other groups, such as crustaceans and birds, may also be affected. Furthermore, most studies focus on single-insecticide exposure and very little is known concerning the impact of neonicotinoid mixtures on aquatic invertebrates. The present study was designed to test potential toxicological effects of an environmentally relevant mixture of imidacloprid, clothianidin, and thiamethoxam on populations of Ceriodaphnia dubia and Daphnia magna under controlled conditions. Chronic toxicity tests were conducted in the laboratory, and survival and reproduction were measured for both species under exposure to nominal concentrations of imidacloprid (0.256 µg/L), clothianidin (3.11 µg/L), thiamethoxam (1.49 µg/L), and a mixture of the three compounds at the same concentrations of the individual compounds. The neonicotinoids did not affect the survival of C. dubia and D. magna founders. Reproduction of C. dubia was affected only by the mixture. All three individual insecticides as well as the mixture caused a significant reduction in the reproduction of D. magna. Our results highlight the complexity of pesticide toxicity and show that traditional toxicological approaches such as acute mortality studies, especially tests with single compounds, can underestimate negative impacts that occur in the environment.HighlightsNeonicotinoids are currently the most frequently used insecticides worldwide.An environmentally relevant mixture of three neonicotinoids was evaluated on two daphniid species.The mixture negatively affected the reproduction of C. dubia and Daphnia magna.Traditional toxicological approaches with single compounds may underestimate the effects occurring in the environment at low concentrations.