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

A detailed comparative study of Recent benthic foraminiferal populations was 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 total of 78 benthic foraminiferal species belonging to 19 families were identified. Porcellaneous forms were dominant, comprising 65% and 68% of the total 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 domestic effluents. Increasing pollution results in low species diversity and population density, associated with an increase in tolerant or opportunistic species. The extent to which population was found to be impoverished corresponded to the degree to which the sediment was contaminated. In this contaminated environment, foraminiferal tests were stunted and aberrant tests were frequently found. Species diversity and population density were higher in Miami Bay (domestic sewage) and deformed forms were scarce. X-ray microanalysis reveals that living deformed specimens contain higher levels of heavy metals (Pb, Zn, Cu, Cr, and Cd) than non-deformed ones. This strongly suggests that heavy metals are responsible for the abnormalities in foraminiferal 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 bioindicators for monitoring coastal pollution. (C) 2001 Elsevier Science B.V. All rights reserved.