Utilização de Chironomus sp (Diptera, Chironomidae) para a avaliação da qualidade de sedimentos e contaminação por metais
Data
2017-11-15
Autores
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Biblioteca Digital de Teses e Dissertações da USP
Universidade de São Paulo
Escola de Engenharia de São Carlos
Universidade de São Paulo
Escola de Engenharia de São Carlos
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O objetivo do presente estudo foi avaliar a viabilidade do uso das espécies Chironomus xanthus e Chironomus riparius na avaliação da qualidade de sedimentos e da contaminação por metais por meio de diferentes ensaios ecotoxicológicos. As amostras de sedimento foram coletados no rio Monjolinho e tributários (14 estações de amostragem). Foi realizada a análise da qualidade da água e do sedimento do sistema utilizando diversas variáveis, tais como nutrientes e metais, sendo possível observar um gradiente crescente de contaminação da nascente em direção à foz do rio Monjolinho. As concentrações dos agrotóxicos organoclorados foram superiores àquelas estabelecidas pela resolução CONAMA 357/05 em apenas algumas estações. Os resultados dos bioensaios laboratoriais com sedimentos indicaram toxicidade aguda em duas estações (Federal e Usina) e nos ensaios in situ observaram-se maiores porcentagens de mortalidade em relação aos ensaios laboratoriais. Os metais Cd e Cu estiveram acima do limite estabelecido pela resolução CONAMA 357/05 em algumas estações de amostragem e, portanto, foram utilizados nos testes de toxicidade aguda e crônica com C. xanthus. Observou-se para o IV instar a \'CL IND.50\' 96h de 0,30 mg/L de Cu e de 0,70 mg/L de Cd. Os testes crônicos com o I instar foram realizados utilizando as concentrações de 1,0 e 70,0 \'mü\'g/L de Cd e 20,0 \'mü\'g/L de Cu e tiveram duração de 16 dias. Na concentração de 1,0 \'mü\'g/L de Cd os resultados foram similares aos apresentados para o controle, exceto para a deformidade do mento. Na concentração de 70,0 \'mü\'g/L de Cd os efeitos foram a redução na sobrevivência, no tamanho do corpo, cápsula cefálica e atraso no tempo de emergência (3 dias). Na exposição ao Cu, não foi observada diferença significativa em nenhum parâmetro analisado quando comparado ao controle. Nos testes de evitamento com C. riparius, verificou-se que as larvas de I instar não evitaram o sedimento contaminado com 2,0 mg/L de Cu e as larvas de II ínstar não evitaram compartimentos com as maiores concentrações de Cu (3,4 mg/L) promovido no experimento de fluxo contínuo. As fêmeas adultas depositaram seus ovos tanto no meio contaminado (1,3 mg/L de Cu) quanto no meio não contaminado, indicando a não preferência. Porém, observaram-se efeitos adversos nas taxas de eclosão e viabilidade dos ovos e das larvas. Com esses resultados conclui-se que as espécies C. xanthus e C. riparius podem ser utilizadas em estudos de toxicidade de sedimentos e de avaliação de risco ecológico, como na contaminação por metais, porém, diferentes parâmetros de avaliação do teste devem ser estudados e cuidadosamente utilizados dependendo da finalidade do estudo.
The purpose of this study was to evaluate the use of Chironomus xanthus and Chironomus riparius to assess sediment quality and metal contamination using different ecotoxicological bioassays. Sediment was collected from Monjolinho river and tributaries (14 sampling stations). Water and sediment analyses were performed by different variables including nutrients and metals. There was an increase of the contamination levels from the fountainhead to the mouth of the river. Organochloride pesticide showed high concentrations (above CONAMA 357/05) in a few number of sampling stations. Laboratory bioassays with sediment demonstrated acute toxicity in two sampling stations (Federal and Usina), and in situ bioassays showed higher percentages of mortality than laboratory bioassay. Acute and chronic toxicity tests were performed with C. xanthus exposed to Cd and Cu. These metals were selected because they presented concentration values above limit established by the CONAMA resolution 357/05. The \'LC IND.50\' 96h for 4th instar larvae was 0.30 mg/L of Cu and 0.70 mg/L of Cd. Chronic tests were carried out in 16 days using 1st instar larvae; the test concentrations were 1.0 and 70.0 \'mü\'g/L of Cd and 20.0 \'mü\'g/L of Cu. No differences were observed between control and 1.0 \'mü\'g/L of Cd, except to mentum deformities. Adverse effects were observed at 70.0 \'mü\'g/L for Cd. These effects were reduction in survival, body length and cephalic capsule width, as well as, emergence time delay (3 days). No differences were observed between control and treatment in relation to Cu. Avoidance tests using C. riparius showed that 1st instar larvae did not avoid sediment contaminated with 2.0 mg/L of Cu. Similarly, 2nd instar larvae of C. riparius submitted to the flow-through system did not avoid the compartments with the higher concentration of copper (3.4 mg/L). Egg-laying females deposited egg-masses in both contaminated (1.3 mg/L of Cu) and uncontaminated media. Therefore, there was no preference in relation to oviposition. On the other hand, adverse effects were observed for eclosion and eggs hatchability. The conclusion is that C. xanthus and C. riparius can be used in toxicity bioassays to asses sediment quality and ecological risk, like metal contamination, but different end points have to be selected and applied carefully used depending on the study purpose.
The purpose of this study was to evaluate the use of Chironomus xanthus and Chironomus riparius to assess sediment quality and metal contamination using different ecotoxicological bioassays. Sediment was collected from Monjolinho river and tributaries (14 sampling stations). Water and sediment analyses were performed by different variables including nutrients and metals. There was an increase of the contamination levels from the fountainhead to the mouth of the river. Organochloride pesticide showed high concentrations (above CONAMA 357/05) in a few number of sampling stations. Laboratory bioassays with sediment demonstrated acute toxicity in two sampling stations (Federal and Usina), and in situ bioassays showed higher percentages of mortality than laboratory bioassay. Acute and chronic toxicity tests were performed with C. xanthus exposed to Cd and Cu. These metals were selected because they presented concentration values above limit established by the CONAMA resolution 357/05. The \'LC IND.50\' 96h for 4th instar larvae was 0.30 mg/L of Cu and 0.70 mg/L of Cd. Chronic tests were carried out in 16 days using 1st instar larvae; the test concentrations were 1.0 and 70.0 \'mü\'g/L of Cd and 20.0 \'mü\'g/L of Cu. No differences were observed between control and 1.0 \'mü\'g/L of Cd, except to mentum deformities. Adverse effects were observed at 70.0 \'mü\'g/L for Cd. These effects were reduction in survival, body length and cephalic capsule width, as well as, emergence time delay (3 days). No differences were observed between control and treatment in relation to Cu. Avoidance tests using C. riparius showed that 1st instar larvae did not avoid sediment contaminated with 2.0 mg/L of Cu. Similarly, 2nd instar larvae of C. riparius submitted to the flow-through system did not avoid the compartments with the higher concentration of copper (3.4 mg/L). Egg-laying females deposited egg-masses in both contaminated (1.3 mg/L of Cu) and uncontaminated media. Therefore, there was no preference in relation to oviposition. On the other hand, adverse effects were observed for eclosion and eggs hatchability. The conclusion is that C. xanthus and C. riparius can be used in toxicity bioassays to asses sediment quality and ecological risk, like metal contamination, but different end points have to be selected and applied carefully used depending on the study purpose.
Palavras-chave
Testes de evitamento, Sedimento, Metais, Chironomus sp, Bioensaios in situ, In situ bioassays, Chironomus sp, Metals, Sediment, Avoidance test