Assessment of the impacts of shrimp farming on nitrogen and phosphorus accumulation in sediments in the São Francisco River basin, Brazil

Abstract

The intensification of anthropogenic activities has significantly contributed to the imbalance of aquatic ecosystems, primarily due to the input of macronutrients whose excess can trigger eutrophication processes, compromising water quality and affecting biodiversity. In this context, the present study aimed to evaluate the contributions of shrimp farming activities in the Lower São Francisco region by analyzing the concentrations of total Kjeldahl nitrogen (TKN), phosphorus (P), and organic matter (OM) in sediments collected from shrimp ponds and the main channel of the São Francisco River. The concentrations of these parameters were compared, and their correlations were assessed. The results revealed significantly higher levels of TKN, P, and OM in the pond sediments, reflecting the accumulation of organic residues from feed and excreta of the cultivated organisms. Statistical analysis showed positive correlations among the nutrients, with a particularly strong association between P and OM (r = 0.97), suggesting that OM decomposition may enhance the release of P into the water column. Multivariate analyses (PCA and HCA) highlighted a clear distinction between aquaculture and riverine environments, with specific clusters based on sediment composition. These findings indicate that shrimp farming contributes to sediment enrichment, potentially intensifying eutrophication processes and jeopardizing long-term ecosystem balance. The study underscores the importance of adopting more sustainable management practices and implementing public policies aimed at monitoring and controlling non-point source pollution, in alignment with the United Nations' Sustainable Development Goals (SDGs) 6 and 14.