Theory of Radioisotopic and Chemical Homeostasis of Marine Ecosystems

In the introduction, the relevance of studies of radioisotopic and chemical interactions in marine ecosystems is justified in terms of the onset of the nuclear era and global industrial revolution associated with the increasing role of the technological use of chemicals, chemical compounds and their radionuclides having various biological significance. The main international programmes and agreements for the protection of seas and oceans from pollution are indicated. The leading approaches to solving problems associated with the interaction of living and inert matter with radioactive and chemical components of the marine environment are described. It is emphasised that the main goal of the studies recorded in international programmes consists in the development of a methodology suitable for assessing the radioactive and chemical contamination of aquatic organisms (hydrobionts) (Translator's Note: Although in some contexts, the term “hydrobiont” is synonymous with the more common English term “aquatic organism”, the former has a special significance associated with its biological role in the context of this work and will therefore be used in most cases.) and bodies of water. Achievement of these goals will make it possible to determine the characteristics of homeostasis of marine ecosystems according to the pollution factor, to develop methodological foundations for marine nature management under conditions of sustainable development of aquatic areas, as well as to predict the evolution of marine ecosystems as a result of climate change and anthropogenic impact. Based on the discussion of literature materials, it is shown that the most effective methods for studying marine ecosystems are associated with the use of semi-empirical models of their material, energy and chemical balance.

The structure of biogeochemical mechanisms is considered in terms of the primary abiotic and biotic factors of the interaction of living and inert matter with the radioactive and chemical components of the marine environment. Chemical substances contained in the waters of the world’s oceans are presented in terms of their radioisotopic composition and physico-chemical forms. It is shown that current rates of anthropogenic influx of chemicals and their compounds constitute a significant factor in the depletion of the carrying capacity of waters. On the example of the transport of fission radionuclides from the site of the accident at the Chernobyl nuclear power plant, it is demonstrated that the influence of hydrometeorological factors manifests itself at different spatial and temporal scales—from diurnal and synoptic in time to global in terms of space. Under nonstationary conditions, the impact of waves, currents, convection and diffusion processes for chemicals or their compounds dissolved in (or not differing in specific density from) water is always directed towards a decrease in the distribution gradients of their concentration in the aquatic environment. Between 1986 and 2000, such trends were identified in the vertical distribution profiles of ⁹⁰Sr and ¹³⁷Cs in the waters of the western halistatic region of the Black Sea. For stationary conditions, the influence of interactive hydrodynamic mechanisms is determined by the ecological carrying capacity characteristics of the aquatic host medium for radionuclides and their isotopic and non-isotopic carriers.

This chapter presents a description of the semi-empirical theory of the mineral and radioisotopic exchange of living and inert matter in the marine environment. It describes methods of parametrisation and verification of differential models of closed systems based on the results of field observations and aquarium experiments using radiolabelling. The scope of applicability of compartment-based balance models is substantiated on the basis of assumptions that the sorption of chemical substrates proceeds in accordance with metabolic reactions of the first or zero orders and that their desorption or intravital excretion by hydrobionts is proportional to their content in living or inert matter. Empirical models have been developed that take into account radioactive decay, the size spectra of allochthonous particles and hydrobionts, the generative and somatic growth of individual marine organism specimens, production processes and the specific mass of living and inert matter in the marine environment, the concentration of radionuclides with their isotopic and non-isotopic carriers, physical and chemical sorption processes, the biotic transformation of physicochemical forms of pollutants, as well as the limitation of primary production processes by biogenic elements in the parenteral and alimentary pathways of the mineral nutrition of aquatic organisms, here referred to as hydrobionts.

In this chapter, the theory of radioisotope and chemical homeostasis of marine ecosystems is presented. The homeostatic characteristics of biogeocenoses are described on the example of models of the balance of material, energetic, mineral and radioisotopic exchange processes taking place in ecosystems of the photic layer. It is shown that the stability of ecosystems is realised by negative feedback loops in accordance with the Le Chatelier–Braun principle. The biogeochemical characteristics of natural homeostasis are demonstrated on the examples of the concentration function of living and inert matter, the adaptation characteristics of aquatic organisms (hydrobionts), the trophic factor, population characteristics of biotopes, as well as the influence of estuarine zones and coastal waters on biogenic elements. Regularities of the formation of limiting fluxes in the self-purification of waters are described according to the criteria of the assimilative capacity, ecological carrying capacity and radiocapacity of the marine environment. Problems in marine nature management arising in connection with the implementation of an ecocentric strategy for the sustainable development of aquatic areas by maintaining a balance between the consumption and reproduction of marine resources are considered. The practical application of homeostasis theory is demonstrated using examples of environmental regulation of pollution by post-Chernobyl radionuclides, organochlorides and heavy metals in Sevastopol Bay, heavy metals in various waters of the Sea of Azov, radioactive and chemical pollution from critical zones of the Black Sea and biogenic elements in coastal waters having liquid outer boundaries.