USE OF OYSTER, CRASSOSTREA-GIGAS, AND AMBIENT WATER TO ASSESS METAL POLLUTION STATUS OF THE CHARTING COASTAL AREA, TAIWAN, AFTER THE 1986 GREEN OYSTER INCIDENT

Most of the oyster mariculture beds in Taiwan are in areas located alo ng the west of the island. One of these areas is the Charting coast, w here green oysters were found in 1986. During this incident, which bec ame internationally notorious, mass mortality occurred in the Charting oyster beds. After this discovery, measures were taken by the authori ties to counter pollution which lead to the problem. The effectiveness of these pollution control actions was evaluated in this study. Two w ater column indicators, particulate and sediment, and oysters were sam pled and analyzed for metals (Cu, Zn, Pb, Ni) in Charting and its neig hboring areas, Kuen-Shen Lake and Shin-Da Harbor, and the control area /station; Dah-Pen Wan. The current study shows that copper and zinc co ncentrations in both oysters and particulates significantly decreased in the Charting area, compared with concentrations found during the pe riod of the green oyster incident. Six years after the incident, the c opper concentration in oysters had fallen from a high of 4400 mu g/g d ry weight to an average of 300+/-69 mu g/g dry weight, figures similar to the copper concentration in 1982. The pollution control actions ta ken after the incident are believed to be the cause of this recovery o f the coastal environment. Nevertheless, Charting still produced oyste rs with the highest copper and zinc concentrations among the areas inv estigated. Further measures currently being taken by the government, i ncluding removing the sediment of some portions of Erhjin Chi, should be able to bring the oyster copper concentrations down to the levels s imilar to those observed in the neighboring area, (average concentrati on below 200 mu g/g dry weight or all time maximum concentration below 500 mu g/g dry weight). Copyright (C) 1996 Elsevier Science Ltd