Diversity models in estuarine systems: benthic patterns and salinity gradients in the Río de la Plata (34°-36°S)

GIBERTO, D.A.; BREMEC, C.S.; SCHIARITI, A.

Aberdeen, Escocia

Congreso; World Conference on Marine Biodiversity 2011; 2011

The relationship between benthic diversity and salinity in estuaries is usually described with quantitative lineal models based on salinity values, without consideration of salinity gradients. We evaluated the existence of a lineal relationship between species richness and environmental data in the Río de la Plata estuary (RLP) (105 sites, 1999-2005). The relationships between different salinity measures and richness were evaluated by simple linear regression (coefficient of variation -CV- as a measure of salinity gradient, annual range, annual average and site salinity), while multiple linear regression was used to assess the importance of other environmental variables. A significant richness-salinity relationship was found (range and CV=negative, average and site=positive). CV explained the highest percentage of variation in diversity (30%). The best multiple model included average salinity, temperature, depth, organic matter and sand content of the sediment (50% of variation). Besides salinity values, rate and magnitude of changes were of great importance to explain diversity in RLP, as expressed by the salinity CV. However, we did not found a robust linear model between salinity and benthic diversity, as previous works carried out in smaller estuaries did. The absence of a sui generis explanation suggests changes in benthic diversity trends with estuarine size.