We aimed in this study utilize environmental indicators as a quantitative method to evaluate and discuss the nitrogen (TN) and phosphorus (TP) flux by a production stage grow-out (termination) of Nile tilapia (Oreochromis niloticus) in fishpond. The TN and TP load, the mass balance, the input of TN and TP via feed and the converted nutrients in fish biomass are the environmental indicators applied in this study. During the production cycle (128 days), the system exported 15,931 g TN and 4,189 g TP that were related to the amount of feed supplied (r Pearson = 0.8825 and r = 0.8523, respectively), corroborated by the feed conversion ratio (1.61:1). The indicators showed that 26% TN and 45% TP were reversed into fish biomass, 62% TN and 40% TP were retained in the fishpond, and 12% TN and 15% TP were exported via effluent. The largest contribution of nutrients generated by the system and exported via effluent was observed in phase III and IV. This result is supported by the feed conversion ratio 2.14 and 2.21:1 obtained at this phase, a fact explained by the amount of feed offered and the fish metabolism. Application of environmental indicators showed to be an efficient tool to quantify flux of TN and TP produced during the grow-out period of Nile tilapia and therefore, guide management practices more sustainable. Concerning the environmental sustainability of the activity the implementation of best management practices such as the better control of the feed amount offered would lead to a smaller loss of TN and TP to the water. Furthermore, the use of better quality feeds would allow greater nutrient assimilation efficiency.

A qualidade das águas das praias nas cidades litorâneas é essencial para a saúde pública. O conceito de balneabilidade é aplicado quando do contato humano prolongado e direto com a água e onde existe a possibilidade de ingestão da mesma, como nas praias. Por isso torna-se importante entender balneabilidade das praias litorâneas tanto como questão de saúde, como para a indústria do turismo. O município de Itanhaém, objeto do estudo está localizado no litoral sul do estado de São Paulo, na Região Metropolitana da Baixada Santista. O objetivo desta pesquisa foi analisar as condições de balneabilidade de doze praias do município de Itanhaém, SP-Brasil, frente aos corpos hídricos, que chegam nas praias, e as condições de saneamento, entre 2010 e 2020. Para tanto foram utilizados dados secundários disponibilizados pela Companhia Ambiental do Estado de São Paulo. A maioria das praias de Itanhaém-SP tem valores anuais de balneabilidade considerados regulares, no período estudado. Foi observada uma melhora na qualidade da água dos corpos hídricos que chegam a essas praias, que pode ser um reflexo do aumento de domicílios com coleta de esgoto. Espera-se que com a melhoria dos serviços de saneamento, as praias se tornem mais seguras aos turistas e moradores do município.

Aquaculture is composed of various themes of interest, particularly does eutrophization due to feeding have direct effects on fish ponds and the whole aquatic system. This study focused on the study of the water quality of an aquatic system related to Nile tilapia (Oreochromis niloticus) rearing. Sampling was done at six sites during one rearing cycle (six months), taking water from the source of water supply, the fish pond itself, the effluent of the fish pond and the mixed waters. A principal component analysis revealed that, among all the environmental variables analyzed, chlorophyll-a, total nitrogen and phosphorus and organic matter were responsible for the variations observed during the rearing cycle. Other sources of variability extrinsic to the fish pond make it evident that the assessment must take the entire aquatic system related to the rearing into consideration, minimizing negative effects.

Aim Our objectives were to recognize species that can serve as biological descriptors and evaluate the changes in the phytoplankton community throughout the grow-out period of the Nile tilapia (Oreochromis niloticus Linnaeus 1758) related to management practices and to limnological variables. Methods Samples from the inflow water and the fishpond were collected for the analysis of limnological variables and the structure of the phytoplankton community. Results In the fishpond, we registered a 1.5 times increase in nitrogen and total suspended solids and a 2 times increase in phosphorous compared to the inflow water. During the grow-out period (113 days), 134 taxa belonging to 10 taxonomic classes were registered. Chlorophyceae (60 taxa) and Cyanobacteria (26 taxa) showed the greatest diversity and abundance of species. The largest biovolumes were recorded in the fishpond. Nanoplanktonic species were the most abundant and represented 35% of the descriptor species in the phytoplankton community of the fishpond. Conclusions The instability of the system associated with the control of the hydraulic retention time as a consequence of management practices, favored the presence of species with small cellular dimensions. The decrease in air and water temperature registered at the end of the grow-out period probably favored the increase and persistence of diatoms. Graphical abstract Spatial variation of the main phytoplanktonic taxa in the fishpond.