Mussels (Mytilus galloprovincialis) as a bio-indicator species in radioactivity monitoring of Eastern Adriatic coastal waters

• 7Be, 40K, 226Ra, 232Th, 238U and 137Cs in mussels along Croatian Adriatic coast.
• Seasonal and spatial variations for the period 2009–2013.
• Higher activities of 7Be in spring versus autumn.
• Constant and uniform 40K activities.
• Low and uniform levels of 226Ra, 232Th, 238U and 137Cs activities.

Croatian Adriatic coastal waters are systematically monitored within the Mediterranean Mussel Watch Project using mussels (Mytilus galloprovincialis) as a bio-indicator species. The study includes determination of naturally occurring (7Be, 40K, 232Th, 226Ra and 238U), as well as anthropogenic 137Cs radionuclides. Activity concentrations in dry weight of mussels' soft tissue along the Croatian Adriatic coast are presented, with spatial and seasonal variations given and discussed. Samples were collected in spring and autumn for the period between 2009 and 2013. Radionuclides were determined by gamma-ray spectrometry. Activity concentrations of 7Be were the highest in spring periods, especially in the areas with significant fresh water discharges. Activity concentrations of 40K did not vary significantly with season or location. 137Cs activities were low, while 232Th, 226Ra and 238U activities were mostly below the detection limit of performed gamma-spectrometric measurement.