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

Palma, M.B., Costa, K.G. da, Magalhães, A., Flores Montes, J., Pereira, L.C.C. and Costa, R.M. da, 2013. Zooplankton it gl spatial and temporal distribution in an equatorial estuary (Amazon littoral, Brazil). In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.) 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 Taperaçu estuary. Samples were taken at three different stations during neap flood tides in rainy and dry seasons. Samples were taken from the subsurface water with a plankton net coupled to a flowmeter. Additional water samples were collected from the sub-surface in order to determine the chlorophyll-a concentrations. Salinity and pH were measured in situ. The lowest salinity (3.25) was recorded in the innermost station in February (2011), favouring the development of a number of oligohaline species, such as Bosmina sp., Daphnia sp., and Diaphanossoma sp. 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 (4,459,354.58±7,666,682.09 ind.m−3). While the Taperaçu 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 (influenced by rainfall rates) was the main factor controlling the composition and density of the local zooplankton community.