Zooplankton communities in the Fatala river estuary in the Republic of Guinea

The study was carried out from September 2019 to August 2020 in the estuary of the Fatala River in Boffa Prefecture very rich in mining and fishing resources, and coveted by mining and fishing companies. Added to this is agriculture, illegal fishing, excessive logging and salt production, which are practised along the estuary. These activities were not without consequence on the halieutic resources in general and on the zooplankton community in particular. The objective of the study was to characterise the initial state of the study area on the zooplankton population before mining operations useful for assessing the impacts of human activities during future environmental and social impact studies. The samples were taken using the plankton net. Data analysis identified 81 species of zooplankton distributed among 42 genera and 29 families. The meroplankton encountered were essentially composed of decapod larvae (2.60%), polychaetes and fish. The holoplankton group was made up of eight taxonomic groups. Copepods represented by 58 species belonging to 16 families are the most numerous. They constituted 87% of the total number of identified species with the predominance of Paracalanus aculeatus (25.43%). The appendiculars represented 2.49%, the Chaetognates, 2.10% and the malacostraca, 1.67% of the zooplankton. The zooplankton density varied according to the stations and the tidal phases. At station level, the highest value (2,357.21 individuals/m3) was obtained at station 9 and the lowest (52.51 individuals/m3) at station 1. At tide level, the highest density (5,675.18 individuals/m3) was obtained during high tide and the lowest (4,898.08 individuals/m3) during low tide. These data show that the density of zooplankton in the Fatala River decreases from downstream to upstream.