Unavailability of mercury in saline waters; Field experiment

摘要

Trace metal concentrations in the water column (dissolved and participate), environmental and biological conditions are the parameters determining metal accumulation in marine organisms. To study bioavailability of mercury, marine mussels Mytilus gallopmvincialis were transferred from the clean area (Mali Ston Bay, Croatia) to the experimental station in polluted area (Kastela Bay, Croatia). The experiments were conducted twice (in summer and in winter). During those two experimental periods, each lasting 6 weeks, the mussels, suspended matter (sediment traps), biofouling organisms (plexiglass plates) and water were sampled weekly. At the same station, temperature, pH, O_2, salinity and sea level were measured. Also, meteorological situation (wind direction and velocity, rain quantity and air pressure) was monitored. The results of this study showed that food is the main source of Hg for filter-feeding marine mussels Mytilus galloprovincialis. while water is the main source of Hg for the communities of biofouling organisms. Bioavailability of Hg was higher for mussels and lower for biofouling organisms in winter experimental period. Bioavailability is highly dependent on meteorological and oceanographic characteristics of the experimental area, because they influence both metal content and speciation in water, and metabolic rate and physiological behavior of an organism. Further, biological factors (e.g. age, size) affect mercury uptake in marine organisms.