This work evaluates the quality of Itanhaém Estuary water in Autumn; Winter, and Spring. In each station were collected samples of water and sediment, being collected subsurface, middle, and bottom water to analyze physical-chemistry, chemistry, and ecotoxicological parameters of the water and the concentration of the organic matter and Phosphorus in sediment. It was developed acute toxicity tests with bottom water using like an organism test the specie Daphnia similis. Through the statistical analyzes in the test-t of bioequivalence, it was possible to observe toxicity in the points near the sewage station and the agriculture activities sites. The chemistry analysis demonstrates more nutrients in the points near the sewage treatment plant (STP). Just the total Phosphorus and the phosphate showed concentration superior to the recommended good quality of the water. Human activities like agriculture, livestock, and the discharge of domestic effluents are slowly affecting the quality of the water and sediment in this estuary; this study demonstrates that the sample point near the STP during seasons (after vacation and Carnaval) when the tourism activities increase showed higher contamination of this ecosystem than the other sample points, so it is necessary to improve the treatments to preserve this environment that it is so essential to the fishers and the population.

本工作评价伊坦海姆河口秋季水质；冬天，还有春天。在每个站点采集水和沉积物样品，采集地下、中层和底层水，分析水的物理化学、化学和生态毒理学参数以及沉积物中有机物和磷的浓度。它是使用类似水蚤（Daphnia similis）的生物体试验开发的底水急性毒性试验。通过生物等效性试验t中的统计分析，可以在污水站附近的点和农业活动场所观察毒性。化学分析表明，污水处理厂 (STP) 附近的点中有更多的营养物质。只是总磷和磷酸盐的浓度高于推荐的优质水。农业、畜牧业和生活污水排放等人类活动正在慢慢影响该河口的水和沉积物质量；该研究表明，在旅游活动增加的季节（假期和狂欢节之后），STP 附近的采样点对该生态系统的污染程度高于其他采样点，