VARIATIONS OF TRACE-METAL CONCENTRATIONS IN SEAWATER AND PEARL OYSTER PINCTADA-RADIATA FROM BAHRAIN (ARABIAN GULF)

Concentrations of seven trace metals in oysters (Pinctada radiata) and paired seawater samples from two stations in Bahrain (Arabian Gulf) were determined every 6-8 weeks during the period March 1991-March 1992. The measured annual means in oysters were higher for Pb (7.64 mug g-1) and Cd (2.48 mug g-1) at an offshore Station 2, while Ni was higher in oysters at a nearshore Station 1. For Cu and Mn no differences were observed between oysters of both stations, however, Fe and Zn were higher in oysters of Station 1. No significant difference was observed in concentrations of trace metals in seawater of the nearshore or offshore stations or between individual metals. Seasonal distribution of metals in oysters and water indicated a tendency to increase towards the hot summer months (June, July-September). Generally, metal concentrations were higher in oysters irrespective of the station and the levels of Pb and Cd exceeded the WHO limits.