Estudo da estrutura da comunidade zooplanctonica na Albufeira dos pequenos libombos

Abstract

The present study was carried out in Albufeira dos Pequenos Libombos located in Maputo, between the months of February and April 1998, with a fortnightly sampling frequency. The objectives of this work were: to determine the composition of the zooplankton community and to quantify the different groups represented, to study the Vertical and Horizontal distributions, and to determine which type of zooplankton is the preferred food for planktophagous fish present in the Pequenos Libombos Reservoir. Sampling was carried out using a motor boat, collecting water samples at different depths and locations with the help of a Van Dorn collector, and subsequent analysis under an inverted microscope in the laboratory. Zooplankton was basically constituted by Rotifers, Cladoceros and Copepods. The most abundant zooplanktonic taxonomic group was the Copepods, represented mainly by Nauplius (24 ind/l) and Cyclopoida (20 ind/l). Zooplankton presented a distribution with little variation along the depth, as well as horizontally, between the coastal and pelagic regions. The samples were also analyzed to determine the phytoplankton biomass at different depths and its relationship with zooplankton. Inedible and indigestible phytoplankton groups were dominant (0.18 mg/L) in relation to edible phytoplankton (0.025 mg/L). Edible phytoplankton biomass was negatively correlated with total zooplankton density. Stomach contents of fish species found in Albufeira were also analyzed. Cladocerans were the zooplanktonic food item preferred by juvenile fish, while the large ones were not observed in the water samples collected in the medium.