Biomonitoring of mercury in the Kastela Bay using transplanted mussels

Kastela Bay, located on the central part of east Adriatic coast, is heavily contaminated by mercury. The main source of contamination was a chlor-alka li plant, which was operating for 40 years since 1949. Previous studies sho wed that mercury concentrated in the sediment close to the plant is being d ispersed throughout the bay by remobilization processes. Subsequent remobil ization of mercury buried in the sediment may be harmful to various marine organisms. In order to assess the availability of remobilised mercury to ma rine organisms and to assess the health risk of consumption of shellfish sp ecies from the bay, a monitoring programme was initiated in September 1997. One thousand six hundred specimens of mussels (Mytilus galloprovincialis) of the same size and age, collected in a very clean area, were transferred to four stations in the bay 1.5 m above the sea bottom. Every month during the summer period and every second month in the winter period, 50 mussels w ere taken from each station for the analysis of mercury and monomethylmercu ry (MeHg) content. The results obtained during 1 year of biomonitoring sugg est that the equilibrium concentration in transplanted mussels was establis hed in a relative short period of time. The digestive gland is preferential organ for the accumulation of total mercury. Seasonal variation of mercury content both in the whole soft tissue, and organs (gills and digestive gla nd) was observed at all stations. However, methyl mercury is more concentra ted in soft tissues than in digestive gland and gills, despite the fact tha t it is absorbed through these organs. The mercury levels in tissues were b elow accepted limits for human consumption. Obtained results showed that th e implantation of mussels in an area containing sediment contaminated by me rcury may be a good monitoring tool for the assessment of the availability of remobilised mercury to marine organisms. (C) 2000 Elsevier Science B.V. All rights reserved.