On the basis of experimental data and cytogenetic studies of marine and freshwater invertebrates natural populations it was shown that different species had approximately equal part (%) of full value posterity at the same average level of chromosome mutagenesis for populations, independing on deleterious factors and females fecundity. This phenomenon made it possible to calculate specimens reproductive contribution for species with different females fecundity and to assess expected reduction of population adaptive potential and the increase of ecological risk at different levels of population damage. It is suggested that the adaptation to pollution will be more effective in populations with high female fecundity. Adaptive possibilities of populations and the resistance of posterity were considered as a alternative properties of populations Ranges of chromosome mutagenesis critical levels for different hydrobionts taxons were determined. An algorithm of ecological risk assessment to benthic communities was proposed.

A comparative study on genotoxic effects in worm gen. Nais (Oligochaeta) from two selected areas of elevated natural and artificial radioactivity has been carried out. The areas considered were a lake in the Chernobyl NPP area in Ukraine and a spring-created pond in the Ikaria island, in the eastern Aegean sea, Greece. The chromosome aberrations recorded in worm Nais pseudobtusa from the lake in Chernobyl were attributed to beta- and gamma-ionising radiation. Unlike these findings, the chromosome aberrations and the pycnotic nuclei observed in worm Nais communis from the spring-pond in the Ikaria island were probably caused by the combined action of low pH, high water temperature and natural radionuclides as heavy metals or/and micro-aggregated one.

The monograph contains results of post-Chernobyl studies of the Black Sea in the fields of radioecology and the inseparably linked radiation ecology and radiochemoecology. Main sources of the data used in this monograph were authors’ own results of measurements of radionuclide concentrations in water, biota and bottom sediments, as well as estimations of radiation effects on aquatic organisms obtained by the IBSS Department of Radiation and Chemical Biology (DRChB) in the Black Sea basin and in the neighboring areas including reservoirs near the Chernobyl NPP and the Aegean Sea. These data were collected in 1986-2006 during 38 marine cruises and in numerous coastal and land expeditions. The studies of DRChB were carried out in the framework of national and international projects headed by NASc. of Ukraine, IAEA, EU and the International Union of Radioecology. During the work, DRChB has performed standardization and intercomparison of radionuclide measurements organized by IAEA Marine Environment Laboratory (Monaco). These intercomparison exercises have involved radiometric laboratories of all the Black Sea countries, Ukrainian Research Hydrometeorological Institute of the Ministry of Ecology and Natural Resources (Kyiv), Joint Institute of Nuclear Researches (Dubna, Russia), Woods Hole Oceanographic Institute (USA) and RISO National Laboratory (Denmark). Results of 4300 radionuclide measurements have been included in the DRChB’s database using software PARADOX 3.5, and they were integrated into IAEA database on marine radioactivity GLOMARD. The main scientific concept of the monograph consists in discovery of trends and in research of relationships as well as time scales of radioecological response of the Black Sea ecosystem components to Chernoby] radiation disaster. For marine and fresh-water radioecologists, hydroecologists, biogeochemists, oceanologists, experts on wildlife management of the Black Sea-Azov Sea and the Mediterranean areas, for scientific advisers of administrative agencies in seaside territories, and also for the governmental and international organizations on wildlife management which direct or mediately are connected with use of nuclear energy.

Results of studies on chromosome damages in cells of Stylaria lacustris (Oligochaeta) from Lake Azbuchin located in the exclusion (alienation) zone of the Chernobyl Nuclear Power Plant (NPP) in 2001 are presented. The data obtained were compared with results obtained in 1991 and 1993. It has been shown that the level of chromosome mutagenesis in cells of this oligochaete did not lower for the period after the Chernobyl accident.

Approaches to the identification and equi-dosimetric assessment of radiation, chemical and combined effects on natural populations of aquatic organisms are proposed. These approaches are based on the generalization of author's previous experimental data concerning separate and combined effects of ionizing radiation and chemical mutagens (heavy metals and organochlorine compounds) on crustacean and fish embryos, as well as on results of field investigations carried out before and after the Chernobyl accident. It is proposed to use the following criteria for the identification and equi-dosimetric evaluation of damaging factors: a comparison of cytogenetic effects in mutagen equivalent doses, distribution patterns of chromosome aberrations in cells, and a mean number of aberrations per an aberrant cell.

The numbers and state of pelagic fish eggs has been compared with the conditions (in particular, hydrochemical conditions) in the waters of the semi-closed Sevastopol Bay and in adjacent marine areas. There are indicated the main zones of toxic and mutagenic influence of various, both natural and anthropic, factors acting in the water areas.

In the present study, an effort is attempted to record the impact of chronic radiation on natural aquatic populations exposed to protracted doses (lower if compared to intervention levels but higher if compared to typical background) and to chemical pollution. The methodology is based on the analyses of chromosome aberrations observed in cells. Therefore, some preliminary research results on the cytogenetic effects on aquatic organisms of various taxa, in coastal ecosystems are presented, considering some selective regions of elevated natural gamma radiation and conventional pollution. These areas are the geothermal spring areas in the island of Ikaria—Eastern Aegean Sea and the port of Pireus, in Greece. The data are compared to the findings recorded in some organisms collected from the North Aegean Sea the early period after the Chernobyl accident. With regard to the different species examined, a first evaluation of the results is made using the reported field findings for the wide area of Chernobyl. The environmental assessment of the studied areas in terms of radiation impact is based on the cytogenetic injuries observed, and evidence of ecosystem disturbance is also pointed out. The final environmental assessment based on the quantified effects observed in the organisms from the studied areas takes into account a published conceptual model of zones of radiation dose rates and the resulting organism responses in a step function scale.

A detailed investigation of 3 populations of Oligochaete species (Dero obtusa, Nais pseudobtusa and Nais pardalis) has been carried out in a contaminated lake of the close-in Chernobyl zone and in a control lake. Hydrochemical indices and concentrations of heavy metals, chloro-organic compounds and (90)Sr in bottom sediments have been measured. Absorbed doses were calculated on the basis of the results of radiochemical analysis and assessed directly with thermoluminescent dosimeters (TLD). Stimulation of paratomous division (asexual reproduction) was found in one species of worm (D. obtusa), and activation of sexual reproduction in the two other species studied. An increase in the amount of cytogenetic damage in the somatic cells of worms from the contaminated lake was found and an attempt was made to assess the relative contributions of radiation and chemical exposure on the basis of analyses of inter-cellular aberration distributions and the types of chromosome aberrations observed in the cells.

The cytogenetic effects of ionizing radiation on natural populations of aquatic ecosystems in comparison to conventional pollutants, are determined based to the methodology of the distribution pattern of the chromosomal aberrations in cells, as well as, the frequency of the type of the recorded damage. Therefore, in the present study joint research results on the cytogenetic effects on aquatic organisms of various taxa in ecosystems in Greece and Ukraine are presented, considering three areas of study as: a) an area of elevated background levels of natural gamma radiation in the vicinity of the geothermal spa in Ikaria island, b) the wide area of Pireus port in Greece in terms of conventional pollutants, both compared to c) the areas of the two repositories in the wide area of Chernobyl.

Research on intensity and character of reproduction of Oligochaeta (Dero obtusa, Nais pseudobtusa and Nais pardalis) was carried out in 1995-1996 in two water-bodies: a) in the Chernobyl NPP zone near Yanov Village, with a dose rate of 14 microGy h-1 on the surface of the bottom sediment; b) at the Uzh River area (the control water-body). The changes in both intensity and reproduction type were observed in worms at the radioactively polluted water-body. Stimulation of paratomic division in D. obtusa as well as activation of sexual reproduction in two other species were found out along with increasing of amount of cytogenetic damages in somatic cells.

In studying the pattern of chromosome aberration distribution among hydrobiont cells in experimental and natural populations, it has been found that the Poisson distribution of chromosomes among cells occurs under the effect of ionizing radiation and under the combined effect of radiation and a chemical mutagen with a higher efficiency of the former. With the comparable efficiencies of both factors and with the effect of a chemical mutagen alone distribution of chromosome aberrations among cells resembles the geometrical one to a greater extent.

The role of mitotic division in carbon and phosphorus uptake by Ornithocerus and Ceratium natural populations has been investigated The relation of these processes has been revealed. Maximum of algae synthetic activity coincides with the time of minimum cell division.