ANTHROPOGENIC IMPACT ON BENTHIC FORAMINIFERA, ABU-QIR BAY, ALEXANDRIA, EGYPT

Abstract

The present study examines the foraminiferal distribution in recent bottom sediments of Abu-Qir Bay located along the Mediterranean coast of Alexandria, Egypt. Abu-Qir Bay receives substantial amounts of heavy metals from the surrounding industrial area, as well as agricultural and domestic effluents, which makes it one of the most polluted areas along the Mediterranean coast. Information provided by the benthic foraminiferal associations was integrated with geochemical, sedimentological, and water data to characterize the environments. The benthic foraminifera are recognized as potential indicators of pollution in coastal marine environments. Surface sediment samples were collected in two seasons (May and November) from nine sites. Cluster analysis and Canonical Correspondances Analysis reveal a distinct boundary that separates two areas; the more-polluted stations nearshore, and the less-polluted stations offshore The first area is characterized by sediment with high silt and clay content and rich in total organic carbon, and bottom water with relatively high temperatures, but low in dissolved oxygen, salinity, transparency, and pH. Its foraminiferal fauna is dominated by Ammonia tepida, Quinqueloculina lata , and Porosononion spp., which are species considered as pollution opportunists. The second area is characterized by coarser sediment overlain by bottom waters high in dissolved oxygen, and transparent, saline, cold water, and is dominated mainly by Quinqueloculina vulgaris, Elphidium spp., Asterigerinata mamilla, Rosalina macropora, Ammonia beccarii, Triloculina trigonula, Peneroplis pertusus , and Quinqueloculina spp. Heavy-metal pollutants have a deleterious effect on benthic foraminifera that results in reduced population diversity, increased dominance, and deformed tests.