Assimilação de nutrientes por macrófitas flutuantes (Azolla sp. e Salvinia molesta) em simulação de cultivo intensivo de Oreochromis niloticus

Abstract

Due to the expansion of aquaculture activities, issues related to the environmental sustainability of production systems arise through the direct use of water resources, which can affect the quality and quantity of water available in these systems. Given this, it is necessary to search for viable mechanisms that make it possible to minimize such impacts using the available natural resources in a sustainable way. As an alternative to the treatment of these effluents it is possible to use aquatic macrophytes which is normally associated with the use of floating or rooted plants. The aim of this work was to evaluate the efficiency of assimilation of nutrients by floating macrophytes (Azolla sp. And Salvinia molesta) in intensive culture simulation of Oreochromis niloticus (Nile tilapia) in order to verify the effluent treatment which is the best option to be used in biological treatment of fish culture water. A water recirculation system containing a box with a capacity of 250 L was used where the juveniles of Oreochromis noloticus that produced the effluent were allocated, and 9 boxes with 50 L capacity where the macrophytes were placed in a totally random manner. Three treatments (Azolla sp. And Salvinia molesta, Azolla sp. And Salvinia molesta) were used with three replicates each. The variables (water temperature, dissolved oxygen, pH, conductivity, ammonia and nitrite), the water in the culture tank and the boxes containing the macrophytes were measured. The use of aquatic macrophytes for the treatment of fish farming effluents can be considered according to the system to be installed. The results show the need to increase the surface area of the filters containing the aquatic macrophytes, as well as to promote their development completely. Furthermore, it is necessary a longer period of time for the experiment so that in this way, one can evaluate the ability of the macrophytes phytoremediator as in the treatment of these effluents.