Avaliação nictemeral e vertical de variáveis limnológicas em tanque lonado de produção de tilápias

Abstract

Limnological characteristics determine the health of the fish produced and the possible problems in the ecosystem. The objective of this work was to verify the nictemeral and vertical dynamics of limnological characteristics in a tilapia production tank. For this, collections were made during 24 hours with a three-hour interval between collections. To determine the vertical dynamics, the water samples were taken at three depths (5 cm; 35 cm and 70 cm). In the central region of the tank, the water was collected with the help of two hoses, one fixed to the metallodymium and the other to the hypoluminium. The surface was collected manually. In all collections, the following parameters were analyzed: temperature, dissolved oxygen, pH, alkalinity, electrical conductivity, total dissolved solids, total phosphorus, orthophosphate, ammonia and nitrite. It was verified that parameters presented changes in the period of 24 hours. Among the strata, the highest concentration of nitrite in the hypolimnium was observed (P <0.01).