The effect of heavy metals presence on benthic foraminifera communities in the Gulf of Gela (Sicilian Channel)

Benthic foraminifera are very sensitive to oceanographic parameter variations, to which they rapidly response through changes in the abundance and/or richness of their associations and in morphological variations of their shell. Many studies have used benthic foraminifera as bioindicators. We investigated recent benthic foraminiferal assemblages in the Gulf of Gela (Sicilian Channel, Mediterranean Sea), examining their relative abundance, specific richness and morphological abnormalities, to highlight a possible correlation with oceanographic features and the concentration of heavy metals in sediments. Sediment was sampled in summer 2006 using box corers in four stations at increasing distances from a point-source of industrial pollution. We performed hydrological characterization of the study area, grain size analysis and heavy metal determinations in sediments, and quantitative and qualitative analyses of benthic foraminifera. Heavy metal analyses highlighted very high mercury and cadmium concentrations in the station nearest the pollution source, in which the Dominance index showed the minimum of population density. In conclusion, a positive correlation seems to exist between the abundance of foraminifera and the concentration of cadmium and mercury in the sediment.