Species Composition and Abundance of Zooplankton in Lekki Lagoon, Lagos State

Zooplankton communities serve as critical indicators of aquatic ecosystem health and play a pivotal role in energy transfer within marine food webs. This study investigated the species composition, diversity, and seasonal abundance of zooplankton in Lekki Lagoon, Lagos State, South West Nigeria. Water samples were collected bimonthly from six stations using a plankton net of 55 micrometers mesh size. Identification and enumeration of zooplankton were carried out using a compound microscope following standard taxonomic keys. Shannon-Wiener diversity index, evenness index, and species richness were computed to evaluate community structure. Physical and chemical parameters including salinity, dissolved oxygen, turbidity, and nutrient levels were simultaneously measured. A total of 34 zooplankton taxa were identified, dominated by copepods, rotifers, and cladocerans. Copepods constituted over 60 percent of total zooplankton abundance, with Acartia clausi and Paracalanus parvus being the most prevalent species. Abundance showed marked seasonal variation, with peak densities recorded during the rainy season attributed to increased nutrient input from terrestrial runoff. Strong positive correlations were observed between zooplankton abundance and dissolved organic matter concentrations. Stations near human settlement areas recorded lower diversity indices, suggesting anthropogenic impact. This study provides baseline data for long-term ecological assessments of Lekki Lagoon and highlights the need for controlled urban waste discharge. Keywords: zooplankton, species diversity, Lekki Lagoon, seasonal variation, Lagos.