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Concerns have been raised in recent years on the potential risks related with pesticide mixtures that are likely to be present in agricultural edge-of-field waterbodies. Despite the high use of pesticides in tropical countries like Brazil, studies evaluating pesticide mixtures are especially scarce in the tropics. The insecticide abamectin and the fungicide difenoconazole are the main pesticides intensively used in Brazilian strawberry crop and are hence likely to occur simultaneously. The aim of the present study was therefore to evaluate the toxicity of abamectin, difenoconazole and their mixture to the tropical fish Danio rerio. Laboratory toxicity tests with the individual pesticides indicated 48 h-LC values of 59 μg L for abamectin and 1.4 mg L for difenoconazole. Mixtures of the two pesticides revealed a synergistic deviation of the independent action model. Implications of study findings for the aquatic risk assessment of pesticide mixtures, especially in tropical countries and indications for future research are discussed.

A comparative study of the acute toxicity of the herbicide atrazine to cladocerans Daphnia magna, Ceriodaphnia silvestrii and Macrothrix flabelligera Um estudo comparativo da toxicidade aguda do herbicida atrazina aos cladóceros Daphnia magna, Ceriodaphnia silvestrii e Macrothrix flabelligera Abstract: Aim: In this study we compared the sensitivity of three species of Cladocera, Daphnia magna, Ceriodaphnia silvestrii and Macrothrix flabelligera, to the commercial product of the herbicide Atrazine, the Atrazine Atanor 50 SC® (500 g/L), widely used on crops in Brazil. Methods: Acute toxicity tests were performed at the nominal atrazine concentrations 2. 25, 4.5, 9.0, 18.0, 36 and 72 mg L -1 , on C. silvestrii and M. flabelligera and at 2. 25, 4.5, 9.0, 18.0, 36, 72 and 144 mg L -1 on D. magna. The range of concentrations tested was established in a series of preliminary tests. Results: The toxicity tests showed that the two species naturally occurring in water bodies in Brazil were more susceptible than Daphnia magna. The effective concentrations of Atrazine Atanor 50 SC® (EC 50 -48 h) to the species M. flabelligera, C. silvestrii and D. magna were 12.37 ± 2.67 mg L -1 , 14.30 ± 1.55 mg L -1 and 50.41 ± 2.64 mg L -1 , respectively. Furthermore, when EC 50 observed here for M. flabelligera and C. silvestrii were compared with published values of EC 50 or LC 50 (mg L -1 ) for various aquatic organisms exposed to atrazine, it was seen that these two cladocerans were the most sensitive to the herbicide. Conclusions: Considering these results and the broad distribution of C. silvestrii and M. flabelligera in tropical and subtropical regions, it is concluded that these native species would be valuable test organisms in ecotoxicological tests, for the monitoring of toxic substances in tropical freshwaters. Resumo: Objetivo:Neste estudo comparamos a sensibilidade de três espécies de cladóceros, Daphnia magna, Ceriodaphnia silvestrii e Macrothrix flabelligera quando expostas ao herbicida Atrazina Atanor 50 SC® (500 g/L), amplamente utilizado em plantações no Brasil. Métodos: Foram realizados testes de toxicidade aguda das concentrações nominais de atrazina nos valores de 2,25; 4,5; 9,0; 18,0; 36 e 72 mg L -1 para C. silvestrii e M. flabelligera e de 2,25; 4,5; 9,0; 18,0; 36; 72 e 144 mg L -1 para D. magna. Estas faixas de concentrações foram estabelecidas em testes preliminares. Resultados: Os testes de toxicidade mostraram que as duas espécies que ocorrem naturalmente nos corpos d'água do Brasil foram mais sensíveis do que Daphnia magna. As concentrações efetivas de Atrazina Atanor 50 SC® (CE 50 -48 h) para M. flabelligera, C. silvestrii e D.magna, foram 12.37 ± 2.67 mg L -1 , 14.30 ±1.55 mg L -1 e 50.41 ± 2.64 mg L -1 , respectivamente. Comparando-se os valores de CE 50 da atrazina obtidos para M. flabelligera e C. silvestrii com valores de CE 50 ou CL 50 (mg L -1 ) disponíveis na literatura para diferentes organismos aquáticos observa-se que os cladóceros testados foram mais sensíveis ao herbicida do que os demais. Con...

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Dinoflagellates of the genus Ceratium are generally marine organisms, but rare occurrences in freshwater have been observed in Brazil. In this paper we are recording for the first time the presence of Ceratium furcoides, an invasive species, in a shallow, natural intermittent pool formed at a high-altitude at the southern end of the Iron Quadrangle, an iron-mining district of Minas Gerais State (Southeast Brazil). Samples were collected in October and November of 2010 (rainy period). The population density of this organism observed in Lagoa Seca ("Dry Pool") was very low, at most 4 ind L -1. Mountain lakes are extremely vulnerable to atmospheric deposition of organisms, making them valuable witnesses both of the many forms of impact arising from human activities and of the extended global connections that facilitate the dispersion and introduction of new species over great distances. Studies on the population dynamics of C. furcoides in natural tropical systems are still rare and very recent to the brazilian scenario and hence the monitoring of its dynamics and the potential impact on aquatic communities of its becoming established are essential to an understanding of the process of bioinvasion by this species.Keywords: bioinvasion, dinoflagellate, Ceratium furcoides, high-altitude lake, Minas Gerais. Primeiro registro de Ceratium furcoides (Dinophyta), uma espécie invasora, em um lago temporário de alta altitude no Quadrilátero Ferrífero (MG, Sudeste do Brasil) ResumoDinoflagelados do gênero Ceratium são principalmente marinhos, porém existem raras ocorrências em água doce no Brasil. Neste estudo registramos pela primeira vez a ocorrência de Ceratium furcoides, uma espécie invasora em um lago altitudinal natural raso localizado na porção sul do Quadrilátero Ferrífero, uma área de extração mineral no estado de Minas Gerais. As coletas foram realizadas nos meses de outubro e novembro de 2010 (período chuvoso).As densidades observadas para C. furcoides na Lagoa Seca foram muito baixas, com máximo de 4 ind L -1 . Lagos de altitude são altamente vulneráveis à deposição atmosférica, o que os torna importantes testemunhos não só dos múltiplos impactos derivados de atividades humanas, mas também das extensas conexões globais, que acabam por facilitar a dispersão e introdução de espécies. Estudos sobre a dinâmica de C. furcoides em sistemas tropicais naturais ainda são escassos e por isso, o monitoramento de sua dinâmica e dos impactos potenciais em comunidades aquáticas a partir do seu estabelecimento, torna-se fundamental para o entendimento dos processos relacionados à bioinvasão desta espécie.Palavras-chave: bioinvasão, dinoflagelado, Ceratium furcoides, lago de alta altitude, Minas Gerais.

In order to contribute to the increase of the body of knowledge on the sensitivity of tropical indigenous species to pesticides, acute and chronic toxicity tests were conducted with the neotropical cladoceran Ceriodaphnia silvestrii. Tests were carried out with the active ingredients diuron and carbofuran and one of their commercial formulations, the Diuron Nortox® 500 SC and the Furadan® 350 SC, respectively. For carbofuran, the active ingredient was more toxic than the commercial product, whereas for diuron, the commercial product appeared more toxic. In addition, hormetic effects on fertility were recorded for intermediate diuron concentrations. Acute and chronic toxicity data indicated that C. silvestrii was among the most sensitive invertebrate species for both test compounds. Based on concentrations measured in Brazilian water bodies, these compounds represent ecological risks for causing direct and indirect toxic effects on C. silvestrii and other aquatic organisms. Our results support previous claims on the advantages of using native species to better tune ecological risk assessment of chemicals in tropical ecosystems.