Environment-zooplankton relationships were analysed in Maldonado Bay (Uruguay), an estuarine area between the River Plate and the Atlantic Ocean. This was done through Principal Component Analysis. Most of the environment variability is accounted for, primarily, by the outflow of the River Plate and the inflow of coastal waters which change through the annual cycle, and in the second place by surface water conditions. On the other hand, most of the zooplankton variability is accounted for by 17 taxa abundant in April and February and by one dominant species present only from May to August. A second source of zooplanktonic variability is due to species which occurred in fall only The main observed variabili ty occurred on an annual scale. On it, variations on smaller scales overlap: from one day to another, between Maldonado Bay and the adjacent waters of the River Plate. The main factors involved were different at each scale. The Bay is relatively isolated from adjacent waters, but the degree of isolation varies throughout the year. The influence of coastal water is greater and occurs first outside the Bay. Biological processes may develop under different conditions in the Bay and in the adjacent waters of the River Plate.
Principal component analysis; Seasonal variation; Zooplankton; Ecology; Coastal zone; Environmental conditions; Estuaries; Maldonado Bay