Biomonitoring of Mercury Contamination at Petroleum Production Platforms in the Gulf of Thailand using Transplanted Green Mussel, Perna viridis

Assessment of mercury contamination was conducted using transplanted green mussels (Perna viridis). Mussels were first exposed to HgCl2 at 0.5, 1.0, 2.5, and 5.0 nmol/L for 8 weeks at laboratory conditions. The result showed that Hg level in the water decreased rapidly, while Hg in mussels increased coincidentally with the applied doses. After 8 weeks the Hg, levels in tissue were a thousand-fold higher than that in the water. Mussels were then transplanted to 3 petroleum production platforms for field study. The result revealed that survival and growth rates of transplanted mussels at all 3 stations were in close to each other but significantly lower than that from the reference site. Hg concentrations in the tissues of transplanted mussels ranged from less than 0.010 to 0.173 μg/g, and Hg concentrations in mussel tissues from all stations were significantly increased within 2 months, while Hg levels in mussel tissues from reference site were not changed. Hg levels of transplanted mussels increased with increasing depths of the water. The transplanted mussels showed no signs of any physical anomalies, indicating that transplanted mussels could be maintained for up to 3 months in an un-natural habitat, such as petroleum production platforms, where food is much less abundant.