LAUSR

The human activities generate inputs of pollutants that exacerbate the natural tendency to eutrophication in estuaries. The goal of this study was to investigate the effects of anthropogenic pollution on tintinnid assemblages along the coast of the Río de la Plata Estuary. Our working hypothesis was that the abundance and size structure of tintinnid assemblages are significantly modified by the availability of differently sized food items due the organic pollution and eutrophication. Results showed that a high degree of water quality deterioration was negatively correlated with tintinnid abundance and diversity. Consequently, sites where the concentration of nutrients was still high showed the highest representation of tintinnids with small lorica oral diameter (LOD), especially Tintinnidium balechi, associated with small-sized prey (bacteria, pico-, and nanophytoplankton). Finally, diversity index was maximum at sites where water was less polluted and T. balechi dominance alternates with species with a larger LOD, a phenomenon which is related to the increased size of the available food (microphytoplankton). These results suggest that tintinnid species composition and distribution represent useful predictors of water quality.