Uptake of mercury species by transplanted mussels Mytilus galloprovincialis under estuarine conditions (Krka river estuary)

Biometric features and physico-chemical conditions are responsible for many of the variables for metal concentrations in indigenous populations of mussels. In order to reduce variations and promote the utility of mussels as bioindicator organisms for environmental mercury concentration levels, individuals of approximately uniform biometric characteristics, selected from a culture of 1-year-old mussels Mytilus galloprovincialis, Lmk., were transplanted to four locations in the Krka river estuary and nearby coastal area (Eastern Adriatic coast). Biometric parameters of mussels and their total and methylmercury content were analysed four times over a period of 270 days in 1988/89. It was found that total and methylmercury concentrations were significantly correlated with shell weight, wet weight and dry weight of mussels. The estimate of minimal methylmercury concentration in the water of the Krka River Estuary (approximately 20 pg/l), derived from the mussels data, is in a good agreement with recently determined concentration levels of methylmercury (between 50 and 100 pg/l) in waters of the same area. The accumulation efficiency for methylmercury is about 20–50 times higher than for total mercury. Only 1% of the total mercury content, and 20–50% of the methylmercury content in water filtered by the mussels, is accumulated in the shellfish tissues.