The benthic macrofauna along the estuarine gradient of the Paranaguá estuary

Estuaries are ecosystems marked by the strong variation of the physicochemical parameters of the water body, reflecting in the distribution of local faunal species. In order to evaluate the influence of water geochemical characteristics on aquatic living organisms, the benthic macrofauna of the Paranaguá estuary (South area of Brazil) was sampled seasonally during 2018 at 16 stations along the whole salinity gradient. In parallel, sediment geochemical characteristics (particle size, nutrients and organic matter) and water (salinity, temperature, pH, redox potential) were evaluated. The Paranaguá estuary presented three specific areas according to salinity. Seasonal variations were more intense in the innermost points of the bay, confirming the influence of rainfall on the stratification of the water column in these areas. The innerregion was further marked by higher fine grain concentrations and higher nutrient levels. Species richness of the benthic macrofauna decreased along the salinity gradient, while total density showed increase numbers. Our results suggest that salinity stability and sediment grainsize are the determining parameters in the macrobenthos colonization dynamics of the Paranaguá estuary. •Continental water flux.•Estuarine Gradients.•Influence in Biota.•Benthic Macrofauna.•Richness and Abundance balance.