THE EFFECT OF INCREASED CONCENTRATIONS OF ARTIFICIAL RADIONUCLIDES IN BOTTOM SEDIMENTS OF THE YENISEI RIVER ON CYTOGENETIC AND GROWTH ENDPOINTS OF THE AQUATIC PLANT ELODEA CANADENSIS

Background. The high content of artificial radionuclides in bottom sediments (BS) of the Yenisei River is the main source of radiation exposure of aquatic plants and, hence, increased levels of chromosomal aberrations (CAs) in roots of elodea plants close to the discharge site of the Mining-and-Chemical Combine (MCC) compared to the reference regions. These data were obtained when the MCC nuclear reactor was working, but after the reactor shutdown, radionuclide contents of the BS decreased and so did the levels of CAs in elodea cells. The previous laboratory toxicological experiments with the radioactive BS from the Yenisei River did not show any significant response of cytogenetic and morphometric parameters of elodea plants to the increased level of artificial radionuclides in the BS. These facts require further study.    Purpose. The purpose of this work was to assess morphometric parameters and cytogenetic abnormalities in the roots of the aquatic plant Elodea canadensis growing on bottom sediments with different levels of contamination by artificial radionuclides: in field studies and laboratory experiments. Material and methods. Samples of plants and BS were collected from the Yenisei River, both close to the MCC discharge site and upstream, in the reference regions. Activity concentrations of BS radionuclides were measured using a Canberra gamma-spectrometer (U.S.). Sample preparation and detection of cells with chromosomal aberrations were carried out following conventional procedures. Laboratory experiments were performed with elodea (E. сanadensis) plants collected in the reference region of the Yenisei River. The morphometric and cytogenetic elodea endpoints were recorded in experiments. Results. From 2014 to 2021, after the shutdown of the nuclear reactor of the MCC, the total level of chromosomal aberrations (CAs) of elodea collected near the MCC was found to decrease compared to the time before the shutdown of the reactor. In 2021, the increased total level of CAs, including “Fragments”, in elodea near the MCC discharge site was significantly different from the level of CAs in the reference area. Significant differences in the total level of CAs between the elodea plants from areas near the MCC discharge site and from reference regions were found within the range of radionuclide activity concentrations in BS of 520-1470 Bq/kg. In laboratory experiments, the factor of increased radioactivity in BS led to a decrease in the growth of elodea roots compared to the control but did not affect the shoot length growth. In the experiment with elodea irradiated for 11 days, a significant increase was observed in the number of cells with CAs and the proportion of vagrant chromosomes relative to the control.   Conclusion. The results obtained indicate that the increased concentrations of artificial radionuclides in the BS of the Yenisei River can affect the growth and cytogenetic parameters of elodea. Funding. The study was funded by State Assignment of the Ministry of Science and Higher Education of the Russian Federation (project No. FWES-2024-0024).