Benthic foraminiferal assemblages and morphological abnormalities as pollution proxies in two Egyptian bays

A detailed comparative study of Recent benthic foraminiferal populations wa s conducted at two bays (El-Mex and Miami) located along the Mediterranean coast of Alexandria, Egypt. Nine samples from each bay were studied and a t otal of 78 benthic foraminiferal species belonging to 19 families were iden tified. Porcellaneous forms were dominant, comprising 65% and 68% of the to tal population in El-Mex and Miami bays, respectively. El-Mex is one of the most metal-polluted areas along the Alexandrian coast. It is contaminated by industrial wastes, chiefly heavy metals, as well as agricultural and dom estic effluents. Increasing pollution results in low species diversity and population density, associated with an increase in tolerant or opportunisti c species. The extent to which population was found to be impoverished corr esponded to the degree to which the sediment was contaminated. In this cont aminated environment, foraminiferal tests were stunted and aberrant tests w ere frequently found. Species diversity and population density were higher in Miami Bay (domestic sewage) and deformed forms were scarce. X-ray microa nalysis reveals that living deformed specimens contain higher levels of hea vy metals (Pb, Zn, Cu, Cr, and Cd) than non-deformed ones. This strongly su ggests that heavy metals are responsible for the abnormalities in foraminif eral tests. The study illustrates that the mode of test deformation depends upon the degree of pollution and type of pollutants. Benthic foraminifera reflect human-induced environmental perturbation and they can be used as bi oindicators for monitoring coastal pollution. (C) 2001 Elsevier Science B.V . All rights reserved.