Raquel Aparecida Moreira

Acute and chronic toxicity of diuron and carbofuran to the neotropical cladoceran Ceriodaphnia silvestrii

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.

The use of rotifers as test species in the aquatic effect assessment of pesticides in the tropics

The present study aimed at evaluating the suitability of rotifers as standard invertebrate test species for the aquatic effect assessments of pesticides, with special emphasis to tropical settings. This was done by weighing rotifers against the criteria that are traditionally used for this end. Rotifers are easy to maintain and culture in the laboratory and their (biological) response to chemical stressors like pesticides is well known. As abundant organisms in aquatic ecosystems, they play a key role in energy flow and nutrient cycling. Although they are often considered to have a low sensitivity to pesticides, a sensitivity analysis conducted in this study revealed that they may be more sensitive than the standard invertebrate test species Daphnia magna to fungicides. In addition, few toxicity data were available for rotifers other than Brachionus calyciflorus and these data were almost exclusively acute (EC50) toxicity values. Subsequently, the sensitivity of other rotifers as well as the chronic sensitivity, bioaccumulation potential, and possible role in biomagnification of pesticides in aquatic foodwebs remains largely unknown. Given their greater diversity and ecological role in tropical freshwaters as compared to temperate freshwaters, the use of rotifers in tropical risk assessments and immediate research needs are discussed.

Toxicity of abamectin and difenoconazole mixtures to a Neotropical cladoceran after simulated run-off and spray drift exposure

Aquatic risk assessments of pesticides in tropical countries have often been disputed for being largely based on risk evaluations conducted in temperate regions. Although pesticide sensitivity comparisons between temperate and tropical freshwater organisms have indeed not revealed consistent differences, risk assessments are currently still based on a relatively small tropical toxicity dataset. In addition, greater levels of runoff and spray drift may be expected in tropical than in temperate agroecosystems, indicating that aquatic life in edge-of-field water bodies is likely to be subjected to higher concentrations of pesticides and their mixtures. The aim of the present study was to evaluate the toxicity of Kraft® 36 EC (a.i. abamectin), Score® 250 EC (a.i. difenoconazole) and their mixture to the Neotropical cladoceran Macrothrix flabelligera. Laboratory toxicity tests with the individual formulated products indicated EC50-48h values of 3.1 and 659μg a.i./L given as nominal test concentrations, respectively. Mixtures of the two pesticides revealed a concentration-dependent deviation of the independent action model, with antagonism at low and synergism at high pesticide mixture concentrations. Laboratory toxicity tests were also conducted with microcosm water that was treated with the individual or mixtures through runoff or direct overspray. Microcosm tanks receiving runoff water from experimental soil plots applied with recommended doses of the individual pesticides did not show toxicity to the test organism. Microcosms that received runoff water containing the pesticide mixture, however, did cause a short-term effect on immobility. The microcosms that were treated by direct overspray of both pesticide formulations showed the most pronounced toxic effects. Study findings suggest a potential risk of these pesticides at environmentally relevant concentrations, especially when they are both present.

Effects of diuron and carbofuran and their mixtures on the microalgae Raphidocelis subcapitata

In aquatic environments, organisms are often exposed to mixtures of several pesticides. In this study, the effects of carbofuran and diuron and their mixtures on the microalgae Raphidocelis subcapitata were investigated. For this purpose, toxicity tests were performed with the single compounds (active ingredients and commercial formulations) and their combinations (only active ingredients). According to the results, the toxicity of active ingredients and their commercial formulations to R. subcapitata was similar. In the single exposures, both carbofuran and diuron inhibited significantly the R. subcapitata growth and caused physiological (chlorophyll a content) and morphological (complexity and cell size) changes in cells, as captured by flow cytometry single-cell properties. Regarding the mixture toxicity tests, data fitted to both reference models, concentration addition (CA) and independent action (IA), and evidenced significant deviations. After the CA fitting, dose-ratio dependent deviation had the best fit to the data, demonstrating synergism caused mainly by diuron and antagonism caused mainly by carbofuran. After fitting the IA model, a synergistic deviation represented the best fit for the diuron and carbofuran mixtures. In general, the two reference models indicated the occurrence of synergism in the mixtures of these compounds, especially when diuron was the dominant chemical in the combinations. The increased toxicity caused by the mixture of these pesticides could pose a greater environmental risk for phytoplankton. Thus, exposure to diuron and carbofuran mixtures must also be considered in risk assessments, since the combination of these compounds may result in more severe effects on algae population growth than single exposures.

Life cycle traits of Philodina roseola Ehrenberg, 1830 (Rotifera, Bdelloidea), a model organism for bioassays

This paper describes experimental results on the life cycle of the rotifer Philodina roseola cultured in the laboratory. Detailed information on life-cycle parameters of a certain species provides a deep understanding and contributes to a better knowledge of the role of the species in the community, besides providing data that are basic to other ecological investigations such as secondary production estimates and knowledge for applications such as its utilization as test-organism in ecotoxicological studies. The average duration of embryonic development of P. roseola was 23.88 h, the age at maturity of primipara was 3.5 days and the maximum lifespan was 23 days. The average size of the rotifer neonate was 198.77 µm, the mean size of primipara was 395.56 µm and for adults 429.96 µm. The average fecundity was 1.22 eggs per female per day and the mean number of eggs produced per female during the entire life was 22.33. The deceleration of somatic growth from the start of the reproductive stage represents a trade-off between growth and reproduction that is often seen in micrometazoans. The life history of P. roseola follows the strategy of other bdelloid species characterized by a rapid pre-reproductive development and canalization of most assimilated energy to reproduction after reaching maturity. The differences observed in total fecundity and longevity between our P. roseola cultures and those from previous studies were probably due to differences of intrinsic adaptation of this species ecotypes to the conditions of their natural environments.

Sensitivities of three tropical indigenous freshwater invertebrates to single and mixture exposures of diuron and carbofuran and their commercial formulations

As compared to their temperate counterparts, few toxicity tests have been conducted so far into the evaluation of the sensitivity of indigenous tropical species to pesticides. Especially mixture toxicity assessments appear to be scarce. To contribute to increase our knowledge in this arena, we evaluated the acute toxicity of diuron and carbofuran and their mixtures to the neotropical oligochaetes Allonais inaequalis and Dero furcatus, and the ostracod Strandesia trispinosa. Tests were performed with both the pure active ingredients, as well as their formulated products. The toxicity of the latter to the three test organisms was generally greater than that of the pure active ingredients, although absolute differences were rather small. The sensitivity of the indigenous species was slightly greater than temperate test species from the same taxonomic groups. The concentration addition conceptual model best described the results of the mixture toxicity data. Derived deviations of this model appeared to be dependent on the test organism and as to whether the pesticides were applied as active ingredients or their commercial products. Reported field concentrations of the two pesticides indicate risks to freshwater biota, especially if they are both present. The test species used in the present study are concluded to be suitable candidates as surrogate test organisms in local pesticide risk evaluations.

TOXICIDADE AGUDA DO AGROTÓXICO CARBOFURANO AO CLADÓCERO CERIODAPHNIA SILVESTRII DADAY, 1902

RESUMO: Nos ultimos anos o aumento do consumo de agrotoxicos em todo o mundo tem preocupado agencias nacionais e internacionais em decorrencia dos diversos impactos ambientais e das serias implicacoes a saude humana. Dentre os agrotoxicos, o carbofurano e utilizado amplamente no Brasil em culturas de batata, milho, amendoim, arroz e soja. Como existe o risco deste composto ser carreado por diversos mecanismos ate os corpos d’agua e causar toxicidade a especies nao-alvo, e necessaria a avaliacao dos seus efeitos nestes ecossistemas. O objetivo deste trabalho foi avaliar a toxicidade aguda do carbofurano sobre a especie nativa tropical Ceriodaphnia silvestrii . Para isso, realizaram-se testes de toxicidade aguda, com concentracoes nominais deste agrotoxico. Para o dafinideo C. silvestrii , os valores de CE 50 24 h e CE 50 48 h foram de 1,80 µg L -1 e 0,75 µg L -1 , respectivamente. Os resultados obtidos mostraram que C. silvestrii apresentou elevada sensibilidade ao agrotoxico carbofurano e foi mais sensivel do que as especies de cladoceros de regioes temperadas, de acordo com os dados da literatura. Considerando-se estes resultados e da ampla distribuicao de C. silvestrii em regioes tropicais e subtropicais, sugere-se o uso desta especie em avaliacoes ecotoxicologicas com agrotoxicos em aguas doces tropicais. Palavras-chave: Microcrustaceo. Pesticida. Toxicidade.

COMPOSIÇÃO E ABUNDÂNCIA DO ZOOPLÂNCTON EM UM CÓRREGO URBANO

Resumo : O conhecimento das especies zooplanctonicas tem sido um poderoso instrumento para avaliar modificacoes nos ecossistemas aquaticos, os quais sao submetidos a grandes impactos causados pelas atividades antropicas. A distribuicao e estrutura do zooplâncton em ecossistemas de agua doce sao influenciadas pelo tipo de habitat e pela estabilidade no ambiente. Este rapido inventario tem como objetivo analisar a comunidade zooplanctonica que caracteriza o corrego Santa Maria do Leme no municipio de Sao Carlos, SP a fim de complementar a avaliacao da qualidade da agua e detectar os efeitos de ambientes loticos sobre esta comunidade. Foram registradas as medidas da temperatura da agua, pH, condutividade e oxigenio dissolvido. O zooplâncton foi amostrado com rede de plâncton (68 µm). As amostras foram fixadas com formol na concentracao final 4% e os organismos foram identificados e contados, calculando-se entao a densidade e os indices de diversidade, dominância e equitabilidade. Foram identificadas 18 especies, sendo que para Protozoa e Meroplâncton foi registrada a maior riqueza (seis especies cada); para Rotifera registrou-se tres especies, Cladocera (duas especies) e Copepoda (um taxon). A analise da comunidade zooplanctonica entre os pontos no corrego Santa Maria do Leme revelou um padrao diferenciado na abundância e diversidade de especies, sendo a densidade e a riqueza de especies maiores no ponto P1. Os protozoarios e rotiferos dominaram tanto em termos de riqueza quanto de densidade. O micro-habitat proporcionado pela instabilidade dos locais garantiu uma maior quantidade de materia orgânica em suspensao, favorecendo o microzooplâncton. Palavras-chave : Corrego urbano. Degradacao. Diversidade de especies.

O USO DA CLASSIFICAÇÃO FUNCIONAL DO FITOPLÂNCTON COMO INSTRUMENTO DE MONITORAMENTO AMBIENTAL

Resumo : Algas fitoplanctonicas sao importantes na avaliacao da qualidade da agua, refletindo a dinâmica do ecossistema. O objetivo principal deste estudo foi avaliar a riqueza, abundância e a distribuicao dos grupos funcionais da comunidade fitoplanctonica nas aguas do Parque do Bicao na cidade de Sao Carlos, Sao Paulo. Amostras de agua para analise das variaveis fisicas e quimicas e do fitoplâncton foram coletadas nos meses de abril e agosto de 2013 em tres pontos. A comunidade fitoplanctonica foi analisada atraves da sua densidade, dos grupos funcionais e dos indices biologicos. A analise da comunidade fitoplanctonica do Parque do Bicao revelou uma riqueza expressiva de especies, foram identificadas 30 especies distribuidas em sete classes taxonomicas. As cloroficeas, cianobacterias e diatomaceas foram componentes importantes desta comunidade. As maiores riqueza e densidade foram registradas na amostragem de abril de 2013. Em ambas as amostragens nos pontos P2 (lago) e P3 (lancamento de esgoto) foram registradas as maiores diversidades. A classificacao do fitoplâncton em grupos funcionais evidenciou a ocorrencia de 12 associacoes. Entre estas, o grupo funcional J, representado principalmente por Desmodesmus quadricauda (Turpin) Brebrisson, refletiu claramente as condicoes mais eutroficas dos pontos P2 e P3. A abordagem dos grupos funcionais do fitoplâncton constituiu uma ferramenta util para a compreensao da comunidade fitoplanctonica neste sistema urbano. Conclui-se que a regiao onde se localiza o Parque do Bicao, deve ser considerada para a utilizacao na preservacao do equilibrio natural e protecao das comunidades aquaticas. Contudo, isso so sera possivel quando as medidas que visem a sua recuperacao e preservacao forem efetivamente implantadas. Palavras-chave : Grupos funcionais. Algas. Eutrofizacao.

O EFEITO DA TOXICIDADE AGUDA DO HERBICIDA ATRAZINA PARA O CLADÓCERO MOINA MINUTA HANSEN, 1899

RESUMO: Um dos maiores problemas relacionados com o uso de agrotoxicos e que a maior parte dos produtos aplicados nao chega a atingir os organismos-alvo, sendo carreada pelas aguas das chuvas, percolando solos ou sendo volatilizados, desta forma representando uma ameaca aos ecossistemas como um todo, principalmente os aquaticos. A utilizacao de testes ecotoxicologicos, para a analise dos efeitos toxicos das substâncias quimicas presentes nos agrotoxicos em diferentes niveis de organizacao dos ecossistemas, tem se tornado uma ferramenta cada vez mais importante nas avaliacoes de impacto ambiental. O objetivo do presente trabalho foi avaliar a toxicidade aguda do herbicida atrazina, utilizando o cladocero Moina minuta como organismo-teste. Os testes de toxicidade foram realizados utilizando-se o produto comercial Atanor 50 SC. Para M. minuta as concentracoes testadas foram: 2,25; 4,5; 9,0; 18,0 e 36,0 mg L -1 . O valor medio obtido para a CE 50 – 48-h da atrazina foi 9.39 ± 0.71 e a faixa de sensibilidade desta especie situou-se entre 8,0 e 10,8 mg L -1 , com valor medio de 9.4 mg L - 1 . Ao comparar a CE 50 obtida para M. minuta com aquelas previamente estabelecidas para diferentes organismos aquaticos expostos ao herbicida atrazina, observa-se que esta especie foi na maior parte das vezes mais sensivel a atrazina do que as outras especies testadas. Os resultados obtidos sao promissores tendo em vista a sensibilidade observada para autilizada como organismo-teste. Alem disso, pelo fato de M. minuta ser uma especie facilmente encontrada em corpos de agua em todo o Brasil este cladocero podera ser um organismo alvo ferramenta promissora na avaliacao da toxicidade deste e de outros agrotoxicos, visando a obtencao de subsidios para acoes voltadas a preservacao da diversidade da biota aquatica. Palavras-chave: Cladocera. Atrazina. Toxicidade.