Accumulation of Cadmium, Copper, Lead and Zinc in the Pacific Oyster, Crassostrea gigas, Collected from the Pearl River Estuary, Southern China

Abstract

Oysters are marine bivalve mollusks, which feed on phytoplankton and detrital organic matter by filtering the seawater through their gills. During the filter-feeding activity, pollutants in the water may enter their body through the gills and associate with the detritus indirectly through the digestive tract. Oysters have been used as biomonitors of pollutants in coastal environments because they are very common in most coastal ecosystems, sessile, sufficiently long living, and can accumulate pollutants to high levels without affecting their survival (Presley et al., 1990; Rainbow, 1995). With the rapid economic development and increase in population density in the Pearl River Delta region of Southern China over the past two decades, large amounts of pollutants have been discharged into the Pearl River. Oysters have been used in monitoring metal contamination in this region since the late 1970s (Phillips, 1982, 1989; Wong et al., 1982; Ashton et al., 1991; Cheung et al., 1992). However, most of these studies were conducted with oysters sampled in Hong Kong. There are only few reports of metal levels in oysters from other areas of the Pearl River Delta. Moreover, studies previously carried out in Hong Kong were focused on food safety, very often using samples purchased from the wet market. Results of these studies indicated that there was an increasing trend of heavy metal contamination in oyster tissues over the past two decades. There is a lack of information in other oyster populations along the Pearl River estuary to allow a comparison of heavy metal contamination levels among different oyster populations. In this study we sampled the Pacific oyster Crassostrea gigas from the three main oyster culture areas along the Pearl River estuary and analyzed the levels of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) in their tissue.