Associated Fauna to Eichhornia crassipes in a Constructed Wetland for Aquaculture Effluent Treatment

Water, sediment and associated fauna were studied in a water hyacinth (Eichhornia crassipes) stand of a constructed wetland, used for aquaculture effluent treatment in SE Brazil, in February-April (summer/rainy season) and July-September (winter/dry season). The hydrological regime and decomposition processes had strong impact on the wetland water quality and on the associated fauna composition. Protozoa and Rotifera were at high densities, mainly in the dry season. Vorticella sp. was the dominant species in both seasons. Zooplankton richness, evenness and diversity were high during both seasons, with higher levels during the rainy season. Protozoa diversity and evenness were higher in the dry season when the water volume was lower. Maximum plant residence time in this wetland should be about 60 days.