Physical, chemical and microbiological aspects during the dry and rainy seasons in a pond covered by macrophyte used in aquaculture water supply Aspectos físico-químicos e microbiológicos nas estações de seca e chuva em viveiro coberto por macrófitas usado no abastecimento de água para aquicultura

Aim: The water quality of a pond covered by macrophytes and used as a water supply for aquaculture was evaluated during the dry and rainy seasons; Methods: Six points were established for water sampling, at water inflow and outflow. Samplings were carried out monthly between June 2008 and May 2009; Results: Inflow points P 1 , P 2 and P 3 in the pond had higher nutrient concentrations and high trophic rates. Moreover, capybaras in the area caused sediment suspension and an increase in fecal coliforms. There was significant difference (p < 0.05) in the concentrations of nutrients in water between the dry and rainy seasons. The outflow of water caused by rain carried the material around the pond directly into the water; Conclusions: The system studied was influenced by rain and lack of adequate management of the surrounding area. Water quality was deteriorated by increase in nutrient concentrations, fecal coliforms and reduction of dissolved oxygen in the water during the rainy season. This was due to allochthonous material from the area surrounding the pond that affected negatively the supply system.