Aquatic Plants and Animals in the Chernobyl Exclusion Zone: Effects of Long-Term Radiation Exposure on Different Levels of Biological Organization

The effects of chronic irradiation on aquatic biota within the Chernobyl exclusion zone during 1998–2014 were studied. The absorbed dose rate for hydrobionts of the studied water bodies was registered in the range 1.3 mGy/year–3.4 Gy/year. It is determined that the rate of chromosomal aberrations in the roots of the helophyte plants of the most contaminated lakes and in the cells of the pond snail embryos is on average respectively 2–3 times and 4–6 times higher than the spontaneous mutagenesis level, inherent in aquatic organisms. Leukogram analysis of peripheral blood of fish showed a decrease in part of lymphocytes responsible for the implementation of immunological reactions. An increase was registered in the number of granulocytic elements (neutrophils and pseudoeosinophils), responsible for phagocytic function and involved in allergic and autoimmune reactions. Along with changes in leukograms, an increased level of morphological damages of erythrocytes (deformation of nucleus and cell membrane, nucleus and cytoplasm vacuolization, pyknosis and lysis of cells, forming of microcytes, schistocytes, double nucleus cells and micronuclei) was determined, which is generally for pray fish 4–12 times and for predatory fish 7–15 times higher than in the fish from reservoirs with background levels of radioactive contamination. Analysis of the viability of the seed progeny of the common reed at germination in the laboratory showed that in gradient of absorbed dose rate from 0.03 to 11.95 cGy/year for parental plants in lakes, there is a reduction in technical germination (from 93 to 60 %), germination energy (from 91 to 30 %) and seed viability (from 54 to 38 %). At the same time, the number of abnormalities of seed seedlings significantly increased: necrosis of roots (from 1.3 to 14.7 %); disturbance of gravitropism (from 2.6 to 17.0 %); damages of organogenesis (from 4 to 24 %) and disturbance of chlorophyll synthesis (up to 2 %).