Sensitivity of Ethiopian aquatic macroinvertebrates to the pesticides endosulfan and diazinon, compared to literature data

Ecotoxicology, May 2016

The aims of the present study were to present a methodology for toxicity tests that can be used when analytical resources to verify the test concentrations are limited, and to evaluate whether the sensitivity of a limited number of Ethiopian species to pesticides differs from literature values for, mainly, temperate species. Acute toxicity tests were performed using three Ethiopian aquatic invertebrate species, one crustacean (Diaphanosoma brachyurum) and two insects (Anopheles pharoensis and Culex pipiens) and using the pesticides endosulfan and diazinon. All species–pesticide combinations were tested in duplicate to estimate the consistency, i.e. the intra-laboratory variation, in test results. Daphnia magna was tested as well to allow the test results to be compared directly with values from the literature. Results indicate that the differences between the EC50s obtained for D. magna in this study and those reported in the literature were less than a factor of 2. This indicates that the methodology used is able to provide credible toxicity values. The results of the duplicated tests showed intra-laboratory variation in EC50 values of up to a factor of 3, with one test showing a difference of a factor of 6 at 48 h. Comparison with available literature results for arthropod species using species sensitivity distributions indicated that the test results obtained in this study fit well in the log-normal distribution of the literature values. We conclude that the methodology of performing multiple tests to check for consistency of test results and performing tests with D. magna for comparison with literature values to check for accuracy is able to provide reliable effect threshold levels and that the tested Ethiopian species did not differ in sensitivity from the arthropod species reported on in the literature.

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Sensitivity of Ethiopian aquatic macroinvertebrates to the pesticides endosulfan and diazinon, compared to literature data

Ecotoxicology Sensitivity of Ethiopian aquatic macroinvertebrates to the pesticides endosulfan and diazinon, compared to literature data Berhan M. Teklu 0 1 2 3 Negussie Retta 0 1 2 3 Paul J. Van den Brink 0 1 2 3 0 College of Natural Sciences, University of Addis Ababa , 4 Kiklo Campus, Addis Ababa , Ethiopia 1 Department of Aquatic Ecology and Water Quality Management, Wageningen University, Wageningen University and Research centre , P.O. Box 47, 6700 AA Wageningen , The Netherlands 2 & Paul J. Van den Brink 3 Alterra, Wageningen University and Research centre , P.O. Box 47, 6700 AA Wageningen , The Netherlands The aims of the present study were to present a methodology for toxicity tests that can be used when analytical resources to verify the test concentrations are limited, and to evaluate whether the sensitivity of a limited number of Ethiopian species to pesticides differs from literature values for, mainly, temperate species. Acute toxicity tests were performed using three Ethiopian aquatic invertebrate species, one crustacean (Diaphanosoma brachyurum) and two insects (Anopheles pharoensis and Culex pipiens) and using the pesticides endosulfan and diazinon. All species-pesticide combinations were tested in duplicate to estimate the consistency, i.e. the intra-laboratory variation, in test results. Daphnia magna was tested as well to allow the test results to be compared directly with values from the literature. Results indicate that the differences between the EC50s obtained for D. magna in this study and those reported in the literature were less than a factor of 2. This indicates that the methodology used is able to provide credible toxicity values. The results of the duplicated tests showed intra-laboratory variation in EC50 Single-species toxicity tests; Tropics; Ecological risk assessment; Species sensitivity distribution; Africa - values of up to a factor of 3, with one test showing a difference of a factor of 6 at 48 h. Comparison with available literature results for arthropod species using species sensitivity distributions indicated that the test results obtained in this study fit well in the log-normal distribution of the literature values. We conclude that the methodology of performing multiple tests to check for consistency of test results and performing tests with D. magna for comparison with literature values to check for accuracy is able to provide reliable effect threshold levels and that the tested Ethiopian species did not differ in sensitivity from the arthropod species reported on in the literature. Introduction The current intensification of agricultural activities in Ethiopia results in a steady increase in both the types and quantities of agrochemicals (Taddese and Asferachew 2008) . Pesticides may, however, cause risks to aquatic ecosystems through contamination by spray drift, run-off, drainage and accidental spills. To prevent environmental harm from the application of these agrochemicals, it is essential to perform a prospective environmental risk assessment before registering a pesticide (Teklu et al. 2015) . Estimating the risks of pesticides to the aquatic ecosystem includes an effect assessment which is often based on acute and chronic laboratory tests of the toxicity of these compounds to aquatic species. Brock et al. (2006) noted the importance of acute toxicity tests with fish, algae and invertebrates for the first tier in the risk assessment of pesticides, in order to identify ecosystem components whose sensitivity should be further evaluated in higher-tier risk assessment procedures (Van den Brink 2013) . These tests also help the retrospective chemical risk assessment, by identifying species that are sensitive to pesticide pollution, so that the presence or absence of a sensitive species in an area may be an indication of the pollution status of that particular area (e.g. Wahizatul et al. 2011) , although the absence of a species may have other causes as well. At present, such an assessment often depends on the results of toxicity tests performed with temperate species, as data on tropical species are scarce (Kwok et al. 2007) . Risk assessments performed for tropical ecosystems should be (partially) based on toxicity data for tropical species, since differences in sensitivity might be expected (Daam and Van den Brink 2010) , although empirical data suggest no systematic differences in sensitivity (e.g. Kwok et al. 2007; Rico et al. 2010) . Gathering sensitivity data for local species enables further examination of whether European and North American data can be extrapolated to other geographical areas (Hose and Van den Brink 2004; Maltby et al. 2005) . Although Ethiopia is located in the tropical region, the risk assessment for pesticide registration is solely dependent on the available temperate acute toxicity data (Teklu et al. 2015) . Only a few toxicity tests have been performed with Ethiopian species, one example being a study (...truncated)


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Berhan M. Teklu, Negussie Retta, Paul J. Van den Brink. Sensitivity of Ethiopian aquatic macroinvertebrates to the pesticides endosulfan and diazinon, compared to literature data, Ecotoxicology, 2016, pp. 1226-1233, Volume 25, Issue 6, DOI: 10.1007/s10646-016-1676-0