ABSTRACT This study evaluates the applicability and reliability of the ABC method as an indicator of the level of organic pollution in non-vegetated tidal flats in a subtropical estuary in southern Brazil. Following a hierarchical sampling design, the method was applied in two contaminated and two non-contaminated tidal flats near Paranaguá. It was conducted in three consecutive fortnights of a summer and a winter, aiming to analyze correlations between faunal responses and chemical indicators of contamination and spatio-temporal variability. Tidal flats closer to the city were classified as grossly contaminated. However, the responses on the non-contaminated area were highly heterogeneous, indicating that natural inputs of organic matter were confounded with pollution effects. In the AIC analysis applied to the W-statistics of the ABC curves, the best model showed correlations with some of the fecal steroids and total organic carbon. Contrary to expected, the ABC curves significantly varied at the smaller spatio-temporal scales due to the high local hydrodynamics and natural organic inputs. This suggests that the ABC method is indeed sensible to the contamination levels and can be used as an index of biotic quality. However, the method must be cautiously applied in estuaries subjected to natural organic enrichment. nonvegetated non vegetated Brazil design noncontaminated Paranaguá winter spatiotemporal spatio temporal variability However heterogeneous effects Wstatistics W statistics carbon expected quality enrichment

RESUMO Com o objetivo de determinar a presença de contaminantes emergentes em corpos aquáticos e avaliar respostas dos grupos dominantes da macrofauna bêntica foram amostrados sete pontos distribuídos ao longo de três rios de mananciais em três campanhas amostrais, na bacia do Alto Iguaçu, Brasil. Foram detectadas concentrações de etinilestradiol, fenofibrato, ibuprofeno e triclosan na água e no sedimento. A fim de correlacionar os padrões de distribuição e abundância da fauna bêntica com os contaminantes encontrados, uma análise de redundância (RDA) foi aplicada e mostrou relações positivas entre grupos taxonômicos indicadores de estresse (como Tubificinae) e alguns dos contaminantes emergentes (como ibuprofeno e etinilestradiol). A análise mostrou, também, que as variáveis mais influentes na distribuição da fauna eram exclusivamente antropogênicas, o que mostra que estes compostos podem ser nocivos e que os rios destinados ao abastecimento recebem cargas poluentes.

ABSTRACT To determine the presence of emergent contaminants in aquatic environments and to evaluate responses of the dominant taxa of benthic macrofauna, seven stations were sampled along three rivers that serve as public water suppliers in three sampling campaigns, in the Upper Iguassu Basin, Brazil. Concentrations of ethinylestradiol, fenofibrate, ibuprofen and triclosan were detected in the water and sediment. To correlate patterns of distribution and abundance benthic fauna with the various contaminants found a redundancy analysis (RDA) was applied and showed positive relationships between faunal groups, that indicate stress (such as Tubificinae), and emerging pollutants (such as ibuprofen and ethinylestradiol). The analysis also showed that the most influential variables in the distribution of the fauna were exclusively anthropogenic, which shows that these compounds can be harmful and that the rivers destined for the supply are receiving pollutant loads.