Zooplankton spatial and temporal distribution in an equatorial estuary (Amazon littoral, Brazil)

Few data are available on the zooplankton communities of the Amazonian littoral zone. Given this, the present study investigated the structure and spatial-temporal variation in these organisms in the Taperacu estuary. Salinity and pH were measured in situ. The highest salinity recorded at this station was 27.88. A total of 68 taxa were identified. The copepods were the most important group. Oithona oswaldocruzi and Acartia lilljeborgii were the predominant species in the rainy and dry seasons, respectively. The highest mean zooplankton densities were recorded during the rainy season at the innermost station. While the Taperacu estuary was dominated by saline waters throughout the study period, both coastal and estuarine species were able to develop during the rainy season. A limited freshwater pulse was observed in the rainy season, when adjacent marshes fed into the estuary, indicating that salinity was the main factor controlling the composition and density of the local zooplankton community.