BYSSUS OF Dreissena.polymorpha AS A BIOINDICATOR OF NI, CD AND CU IN THE SOUTH OF THE CASPIAN SEA: GOOD CORRELATION SOME FRACTIONS OF METALS

Over the last few decades, a large number of studies have been made of the chemistry of estuary, coast and the shelf sediments in order to ascertain the origin of the various elements, especially heavy metals. Small quantities of the metals in living organisms are necessary for food health; excessive quantities of the trace metals are toxic to the organisms. Sever problems can be observed since they accumulate in the tissue of the aquatic organism.

Environmental problems of the Caspian Sea are multiple and various in their origin. Caspian Sea as a land-locked system is becoming increasingly polluted with massive loads of contaminants discharged from various anthropogenic sources, which remain trapped within the basin.

Many heavy metals occur naturally in marine environments, and bivalve mollusks, are well known for their biological features of concentrating heavy metals and other substances in their tissues. These organisms accumulate most of the contaminants at much higher levels than those found in the water column, and they are representative of the pollution of an area. Bivalve species especially have been used as biological indicator organisms to monitor marine environmental pollution by heavy metals and chemicals due to their own properties of inhabitation.

According to Agusa (2004) Pollutants can be accumulate in the fish and transfer to the human food chain. It is important that higher rates of cancer reported in the study area could be associated with fish consumption, because of disadvantage influence on human health. Dreissena polymorpha is fed by mentioned species, so heavy metals accumulate in food chain and affect environmental human health. In this study, heavy metal (Cd, Fe, Zn, Pb, Ni and Cu) contents in coastal sessile species of Bivalvia (Dreissena polymorpha), and surface sediment in southern Caspian were investigated.

The present study showed that all parts of Bivalve had ability to accumulated heavy metals from their environment. The mean concentrations of Pb, Ni, Cd, Zn, Cu and Fe in the D. polymorpha   from south Caspian sea were 5.67, 11.11, 2.69, 115.63, 12.52 and 1849.24 µg/g dry weight in soft tissue ; 40.36, 20.07, 3.85, 10.93, 7.81 and 248.16 µg/g dry weight for shell and 30.38, 28.32, 4.58, 64.78, 23.31 and 7169.49 µg/g dry weight for byssus, respectively. This suggested that, the byssus of D. polymorpha could be potentially as biomonitoring material for environmental concentration of heavy metals in south Caspian Sea. Therefore the use of the byssus of D. polymorpha  as a potential biomonitoring materials is suggested since the significant good correlation coefficients between heavy metals in byssus with some geochemical fraction of metals Ni, Cd and Cu in the surface sediment.