Avaliação do desempenho da macroalga Gracilariopsis tenuifrons em um sistema de aquicultura multitrófica com recirculação

Abstract

The use of a recirculating aquaculture system, integrating seaweeds, has been used as a tool for making cultivations more productive, sustainable and with less risk to animal health. Given this context, this study aimed to verify the performance of Gracilariopsis tenuifrons in a cultivation system with Litopenaeus vannamei using water recirculation. For this purpose, the species were cultivated for 4 weeks, evaluating the physicochemical variables of water (temperature, salinity, pH, suspended material, NO2-, NO3-, NH4+, PO43-) as well as the development of the tested organisms (biomass and RGR). The experimental model was composed of a cultivation tank (220 L) with adult shrimps (45 ind.m-2) connected by gravity to a sedimentation tank (190 L) and, in sequence, to four tanks (100 L) containing the seaweeds (500 g.m-2). A tank with a submerged pump was used to recirculate water in the system. Three seaweed tanks were used as control (seawater without enrichment). As results obtained, among the physicochemical variables of water, the NH4+ concentrations were the one that mostly influenced the seaweed development. The highest concentrations were recorded in shrimp tanks (39,81 mol. L-1 ± 6,16), with significant reductions in seaweed tank outlets at all sampling periods. Thus, the water enrichment enhanced the seaweed development, promoting a 39,42% increase of its biomass in the first week (697,1 g.m-2 ± 20,9), as well as growth rates of up to 4,08 %.d-1 ± 0.38. Furthermore, this species was able to increase its N content in tissue by 4,8 times during the experiment. When comparing the results obtained in the control, we found that the performance of Gp. tenuifrons was significantly superior in multitrophic cultivation in all aspects. The shrimp was not affected by the type of cultivation, being registered a gradual increase in biomass values, with survival rate of 100% at the end of the experiment. Thus, we can conclude that Gp. tenuifrons can be considered an excellent candidate as a component of multitrophic systems using water recirculation, exhibiting high potential for bioremediation of the main metabolites produced by shrimp culture.