Benthic macroinvertebrates as bioindicators of water quality in Billings Reservoir fishing sites (SP, Brazil)

Abastract: Aim The Billings Reservoir is the largest reservoir in the metropolitan region of São Paulo and has multiple uses, including artisanal fishing. Its surroundings present intense occupation, resulting in various environmental impacts. Although the water is degraded, affecting the composition and quality of the fish, this reservoir supports artisanal fishermen who survive through this activity. This study aimed to analyze the water quality in the main sites of artisanal fishing activity, with an emphasis on the benthic community as a bioindicator. Methods Three sampling sites were selected, in which water and zoobenthos samples were collected monthly from April 2012 to March 2013. Water analyses consisted of the determination of pH, temperature, conductivity, turbidity, total dissolved solids, dissolved oxygen, total nitrogen, total phosphorus, and trophic state as well as a principal components analysis. The zoobenthos analysis consisted of determining the relative abundance and total density of taxa, the Shannon-Weaver diversity index, taxa richness, uniformity, Simpson’s dominance index, and the benthic community index and conducting a canonical correspondence analysis. The non-parametric Kruskal-Wallis test followed by the Student-Newman-Keuls test were used to investigate the existence of significant differences in the abiotic and biotic variables among the sites. Results The studied sites showed a high degree of eutrophication, with nitrogen and phosphorus totals levels above the limits defined by current Brazilian legislation. Taquacetuba (P1) showed the best environmental conditions for the development of fishing activity, with the presence of sensitive organisms (Polymitarcyidae) and higher levels of dissolved oxygen. Alvarenga (P2) had the worst water quality, with a predominance of tolerant organisms (Oligochaeta) and lower levels of dissolved oxygen. Conclusion In conclusion, the benthic community in association with abiotic metrics proved to be a useful tool as a bioindicator of environmental conditions, indicating that fishing activity at Alvarenga is not recommended due to the degradation of water quality.