Accumulation Ability of Hydrobionts and Suspended Matter in Relation to Plutonium Radioisotopes in Coastal Waters (Sevastopol Bay, the Black Sea)

The accumulation ability of marine ecosystems biotic and abiotic components is one of the water masses self-purification mechanisms. Hydrobionts and suspended matter accumulate anthropogenic substances from the water, thereby contributing to its self-purification. It is important to study the quantitative characteristics of this process in order to assess the ecological state of aquatic ecosystems and a possible impact of anthropogenic substances on marine organisms and ensure their protection. Anthropogenic substances entering the water systems include technogenic radionuclides. Among them, the plutonium radioisotopes 239+240Pu occupy a special place. Being long-lived alpha-emitting radioisotopes, 239+240Pu are especially dangerous if they enter inside the organism. Therefore, it is required to assess hydrobionts accumulation ability in relation to these radioisotopes, and the dose loads that they create on marine biota. This study was carried out in Sevastopol Bay of the Black Sea which was subjected to pollution by anthropogenic radionuclides and is currently serving as a model object for studying the redistribution of 239+240Pu in marine coastal ecosystems. This work was aimed to assess the accumulation ability of hydrobionts and suspended matter in relation to plutonium and the dose loads created by 239+240Pu on marine organisms, representatives of different trophic levels, based on determining the 239+240Pu activity concentration in the components of the bay ecosystem. Representatives of multicellular brown and green algae, bivalves, demersal and pelagic fish, crabs and zooplankton of the subclass Copepoda were studied. The 239+240Pu activity concentration in the ecosystem components was determined by standard radiochemical methods and alpha-spectrometry. The accumulation ability of hydrobionts and suspended matter in relation to 239+240Pu was estimated by the concentration factors (Cf). The dose loads on marine biota were calculated using the ERICA Assessment Tool 2.0 software package. It was found that suspended matter has the highest accumulation ability among the studied components (Cf 239+240Pu – n·105), as well as bivalve mollusks, perennial multicellular brown algae and pelagic predatory fish among the studied hydrobionts (Cf 239+240Pu – n·103). It is concluded that the processes of plutonium redistribution in the bay lead to its deposition in the bottom sediments and long-term biotic components of the bay. At the same time, 239+240Pu are not removed from the ecosystem and, under certain conditions, they can enter the water as secondary pollution. The critical links of the trophic chain in the bay ecosystem according to the dose loads are determined for the link of primary producers: phytoplankton and perennial brown algae, for consumers of the first order – bivalve mollusks, for consumers of the second order – pelagic predatory fish. The paper contains 5 Figures, 1 Tables, and 48 References.