Factors Determining Benthic Foraminiferal Distribution in the Shallow Water Coastal Environments of Southwest Nigeria Sector of the Gulf of Guinea

摘要

Background and Objective: The dominant factors influencing abundance and distribution patterns of foraminifera in shallow water coastal environments of southwest Nigeria sector of the Gulf of Guinea was undertaken. The objectives were to characterize benthic foraminiferal population in sediments and establish relationships of the identified fauna with depth, salinity, pH, pollutant metals and sediment texture. Material and Methods: One hundred and thirteen surface-sediment samples were analyzed for common pollutant metal and foraminiferal contents and grain size composition. The depth of sediment-water interface, salinity and pH of water collected from selected stations were measured. Results: Organic matter enriched, dark-grey to black mud substrate enabled relatively large quantity of foraminifera at the Northwest portion of the lagoon despite the very low salinity that characterizes the micro-habitat. However, this habitat could only produce a monospecific assemblage whose total population is constituted by over 80% Ammonia beccarii. Few stations in Lagos Harbour were moderately polluted with Zn and are marked by low species diversity and abundance. Substrates seem to influence relative abundance of calcareous porcellaneous and agglutinated foraminifera at the Southwest and Eastern segments of Lagos Lagoon. Conclusion: Consequent upon the non-saline nature, specimens of foraminifera were not recovered from Badagry and Yewa creeks. Moderate pollution of sediments with Zn, Cd, Ni and Cr and the nature of substrates accounted for the disparity in foraminiferal species abundance, diversity and dominance in Lagos Lagoon. However, favourable pH, salinity and substrates facilitated high species variation and abundance in Lagos Harbour.