Assessing macrobenthic compositions and ecological status of Lagos Lagoon using AZTI marine biotic index

Abstract

Coastal lagoons, such as the Lagos Lagoon, are ecologically significant ecosystems that are becoming increasingly vulnerable to human-induced stresses, such as urbanization, pollution, and industrial activity. This study evaluated macroinvertebrate compositions and ecological quality status of the Lagos Lagoon using the AZTI Marine Biotic Index (AMBI) to assess responses to these perturbations. Ten (10) stations were sampled across the Lagoon during both dry and wet seasons. Water and sediment samples were obtained using bottom water samplers and a Van Veen grab respectively, and analyzed for physicochemical parameters and macroinvertebrate compositions using standard techniques. Analysis of variance showed significant seasonal changes (p < 0.05) in water temperature, dissolved oxygen, salinity, conductivity, and total dissolved solids. Ten (10) taxa (abundance: 237 individuals) were recorded during the wet season and 9 taxa (abundance: 226 individuals) in the dry season. These taxa belonged to three phyla: Mollusca, Arthropoda, and Annelida. The Shannon-Wiener diversity index ranged from 0.77 to 1.91 (wet season) and 0 to 1.21 (dry season), suggesting low diversity. Simpson's dominance index ranged from 0.60 to 0.86 (wet season) and 0.08 to 0.74 (dry season). AMBI revealed a slight level of ecological disturbance across all Stations, except Stations 6 and 7, with moderate disturbance in both seasons. The findings improved the understanding of the impact of numerous stresses on benthic macroinvertebrate ecosystems and illustrated the usefulness of biotic indices in ecological assessments.