ECOLOGICAL ASSESSMENT OF PHYTOPLANKTON IN RELATION TO WATER PHYSICO-CHEMICAL PARAMETERS IN THE BAYS OF THE EBRIE LAGOON, COTE D IVOIRE

The Ebrie Lagoon plays a critical role in biodiversity conservation and supports key local activities such as fisheries and tourism. However, rapid urbanization in surrounding districts (Cocody, Koumassi, Vridi, Plateau)has contributed to increasing pollution and ecological disturbances.This study assessed the relationship between physicochemical parameters and phytoplankton abundance in selected bays of the lagoon. From February to November 2020, samples were collected using vials and a 20 um mesh plankton net in areas exposed to strong anthropogenic pressure.A total of 53 taxa,distributed across five phyla(Heterokontophyta, Dinophyta, Cyanoprokaryota, Euglenophyta, Chlorophyta), were identified. A bloom of Skeletonemacostatum occurred at the Vridi Zimbabwe station during the short rainy season, while phytoplankton abundances remained low during the major rainy season. The results revealed strong spatial and seasonal variability in physicochemical parameters,driven by river inputs,marine intrusions,and human activities. These findings indicate that phytoplankton distribution in the Ebrie Lagoon is highly dependent on environmental conditions, providing insights into the dynamics of primary production in this vulnerable ecosystem.