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A Lagoa de Extremoz, localizada na zona metropolitana de Natal, Nordeste do Brasil, e um importante reservatorio urbano que contribui para abastecimento de aproximadamente 300 mil pessoas. Devido a importância desse corpo hidrico para manutencao e desenvolvimento das atividades humanas, e importante conhecer como a qualidade da agua e sedimento deste ambiente varia ao longo do tempo e do espaco. Em 2013 foram realizadas quatro coletas, duas quando o nivel de agua da lagoa era inferior a 45% de sua capacidade (abril e maio) e, depois, quando o nivel de agua da lagoa estava no maximo de sua capacidade (julho e agosto), sempre em dois pontos na Lagoa de Extremoz e um no Rio Guajiru. Essas amostragens foram necessarias para avaliar as concentracoes de metais (Zn, Cu, Pb, Cd, Cr, Fe, Ni) no sedimento superficial, e sua relacao aos resultados de testes ecotoxicologicos realizados em agua e sedimentos. A extracao dos metais foi realizada por solucao mista (HCl 0,5 mol.L-1 + H2 SO4 0,012 mol.L-1) e analisada por Espectrometria de Absorcao Atomica (EAA). Os ensaios ecotoxicologicos cronicos usaram Ceriodaphnia dubia e C. silvestrii para analise da toxicidade da agua e Hyalella azteca para sedimento. Foram realizadas analises no sedimento para determinar os teores de materia orgânica - MO (incineracao em mufla a 600 oC), de carbonato (solubilizacao com acido acetico a 4%) e a granulometria (peneiramento simples). Os resultados sugerem riscos as comunidades de crustaceos bentonicos e, consequentemente, a todo o ecossistema da lagoa, atribuidos principalmente ao aporte antropogenico de Zn, Cu, Pb e Cd, a correlacao positiva de MO, CaCO3 e porcao siltico-argilosa, bem como a frequencia de amostras com efeito toxico cronica ao Hyalella azteca. Abstract The Extremoz Lagoon located in the metropolitan area of Natal, Northeast Brazil, is an important reservoir that helps to supply approximately 300,000 people. Due to the importance of this water body for maintenance and development of human activities, it is important to know how the quality of the water and sediment of this environment varies over time and space. Four samples were taken in 2013, two when the level of the water was less than 45% of capacity (april and may) and then when it reached the full capacity (july and august), always two points in Extremoz Lagoon and one in Guajiru River. These samplings were needed to evaluate the concentrations of metals (Zn, Cu, Pb, Cd, Cr, Fe, Ni) in the surface sediment, and its relationship to the results of ecotoxicological tests on water and sediment. The metals extraction was performed by mixed solution (0.5 mol L-1 HCl + H2 SO4 0.012 mol L-1) and analyzed by Atomic Absorption Spectrometry (AAS). The chronic ecotoxicological tests used Ceriodaphnia dubia and C. silvestrii to analyze the toxicity of the water and Hyalella Azteca for sediment. Analyses were performed in the sediment to determine the levels of organic matter (incineration in mufle furnace at 600 °C), carbonate (solubilization with acetic acid 4%) and particle size (single screening). The results suggest risks to the benthic crustaceans communities and consequently to the entire ecosystem of the lagoon, attributed mainly to anthropogenic contribution of Zn, Cu, Pb and Cd, to the positive correlation of MO, CaCO3 and siltic-clay portion, as well as the frequency of samples with chronic toxic effect to Hyalella azteca.

Ecotoxicological evaluation of water and sediment of an urban and coastal water reservoir in northeastern Brazil