Abstract:
Comparative studies of species and of total amount of vibrio bacteria in seawater, oysters and sediments, in oysters culture area in Tambon Angsila, Chonburi province were carried out in January, May and October 2004. The total amounts of vibrio bacteria in seawater, oysters and sediments were found in the range of, respectively. The highest number of total vibrio bacteria in seawater and sediment was detected in January whereas in oyster was detected in May. The numbers of total vibrio bacteria in seawater, sediment and oyster collected from submerged rocky zone were higher than those in raft oyster culture zone, in most sampling period. In January and May, V.alginolyticus and V.parahaemolyticus were the dominant vibrio bacterial species. However, the number of these two species was reduced while V.anguillarum was increased in October. The concentration of total vibrios bacteria and V.parachaemolyticus in oyster was higher than that of the standard for human consumption during most sampling period. These results indicated the potential risks of food poisoning associated with raw oyster consumption.The concentraions of Hg, Cd, Pb, Cu, Ni, Zn and Fe in sediments from oyster culture area were found in hte range of 0.019-0.038, 0.043-0.054, 8.67-10.93, 6.81-8.87, 5.50-5.76 and 17.69-29.30 ug/g dry weight, respectively. The concentrations of Hg, Cd, Pb, Cu, Ni, Zn and Fe inoyster were found in the range of 0.003-0.005, 0.18-0.25, 0.06-0.13, 23.72-73.42, 0.13-0.25, 89.2-280.4, 34.41-41.38 ug/g wet weight. Heavy metals in sediments in sediments and oysters showed clear seasonal variation. Heavy metal concentrations in sediment and oyster from both area and culture technique showed no significant difference. However, Fe, Ni and Pb contents in sediments had positive co-relations with % ignition loss. The present levels of Hg and Cd in the sediment were slightly higher than those previously recorded. The concentrations of heavy metals in oysters were well within the acceptable levels for consumption except for Cu and Zn, which were higher than those of the standard for human consumption in most sampling period.