Spatial and Seasonal Variation in Physicochemical Characteristics and Zooplankton Composition Across Upper Lagoon, Industrial and Marine Ecological Zones of the Lagos Ship Channel, Nigeria

Abstract

The Lagos Ship Channel is a major coastal waterway that links Lagos Lagoon with the Atlantic Ocean and supports diverse ecological processes, fisheries, and maritime activities. However, information on how environmental gradients influence zooplankton community structure within the channel remains limited. Hence, the objective of this paper was to investigate the spatial and seasonal variation in physicochemical characteristics and zooplankton communities across three ecological zones (Upper Lagoon, Industrial and Marine) of the Lagos Ship Channel, Nigeria using appropriate standard methods. Significant spatial differences were observed in salinity, pH and nitrate concentrations (p < 0.05), demonstrating a pronounced environmental gradient from the Upper Lagoon to the Marine Zone. A total of 19 zooplankton taxa were recorded, with larval forms and cyclopoid copepods dominating the assemblage. The Industrial Zone supported the highest zooplankton abundance (1175 individuals), whereas the Marine Zone exhibited the greatest species richness (16 taxa) and Shannon diversity (H′ = 1.799). Although total abundance did not differ significantly between seasons (p > 0.05), species richness and diversity were significantly higher during the wet season (p < 0.05). The findings demonstrate that environmental gradients strongly structure zooplankton community composition within the Lagos Ship Channel and highlight the ecological importance of the channel as both a productive nursery habitat and a reservoir of aquatic biodiversity. These results provide valuable baseline information for biodiversity conservation, fisheries management and long-term ecological monitoring of Nigeria's coastal ecosystems.