Investigation of the natural radionuclides enrichment in the biosystem of aquaculture in İzmir-Gerence Bay

Studies on natural radioactivity in marine ecosystems offer considerable scope for understanding the mechanism of radioactivity transfer to man through the marine food chain. Aquaculture (the farming of fish,shellfish, and aquatic plants) is among the fastest-growing segments of the world food economy. Aquaculture" stands for producing fish in seas and lakes in net cages or pools on land under the control of humans. Aquaculture and especially fish farming in cages has economical importance for İzmir-Gerence. In this study, it is aimed to determine the correlation between the concentrations of the natural radionuclides (210Po and 210Pb) and water temperature, salinity, chlorophyll a levels in different marine organisms. So, mussels samples were cultivated around fish cages by using mussel net bags. Fish, seawater, sediments and planktonic organisms samples were collected from aquaculture biosystems of İzmir-Gerence Bay. Monitoring of the growth of the mussels in every stage gave us information about the dynamics and transport of radionuclides in different marine organisms. The natural radionuclides 210Po and 210Pb were analyzed in mussels (Mytilus galloprovincialis), fish, seawater, sediment and planktonic organisms samples from aquaculture biosystems of İzmir-Gerence Bay monthly. Water temperature, salinity, chlorophyll-a were determined. The other different station was studied in İnciraltı. Measurements of 210Po were realized through its 5.30 MeV alpha particle emission, using 209Po (0.1 Bq mL-1) as the internal tracer. Maximum growth in length occured during the spring-summer months. In spring and early summer periods, the activity concentrations of 210Po and 210Pb and chlorophyll-a were found to be higher those of other months. This situation is derived from phytoplankton increase called spring bloom and also it is known that natural radyonuclides in the atmosphere comes to the aquatic environment with dry and wet precipitation in spring. Mussels samples which were collected in May showed the highest concentration of radionuclides 984±12 Bq kg-1 for 210Po, 200±5.0 Bq kg-1 for 210Pb. The concentrations of 210Po and 210Pb in planktonic organisms samples varies between 32±2.2 Bq kg-1 and 185±0.2 Bq kg-1, 30±2.0 Bq kg-1 and 180±2.0 Bq kg-1, respectively. In the sediments, 210Po and 210Pb varies between 32±2.2 Bq kg-1 and 185±0.2 kg-1, 30±0.2 kg-1 and 180±0.2 kg-1, respectively. The 210Po and 210Pb concentrations in surface water of during sampling period were around 68±0.2 BqL-1and 23±0.2 BqL-1, respectively. The highest activity concentrations of 210Po, was found 361±6.5 and 25±0.2 Bq kg-1 in hepatopancreas of mussels and fish, respectively. All the data obtained were evaluated statistically by using Principal Component Analysis (PCA). A significant relation was found between the activity concentrations of 210Po and 210Pb and chlorophyll-a (p<0.05). Keywords: İzmir-Gerence Bay, Aquaculture, Mussel, Fish, plankton, sediment, chlorophyll-a, 210Po, 210Pb.