Characteristics of Sea Water Self-Purification Processes in the Black Sea Based on the Results of Biotesting

Abstract

The dynamics of sea water self-purification processes in the water area of the Karadag Nature Reserve during five years after the emergency discharges of sulfur and oil products to the Black Sea has been studied. The toxicity of aquatic environment was estimated by the biotesting method based on using saltwater crustaceans: Artemia salina species from the Branchiopoda order. The rate of self-purification processes in surface and deep levels of sea water was established. The ecological significance of self-purification for restoring the quality of marine aquatic environment was specified. The sea water self-purification mechanisms occurring as a result of mechanical, physicochemical and biological processes are studied. It has been revealed that the incoming pollutants are diluted by marine water of the Black Sea, suspended substances gradually settle down to the bottom, while the organic substances are subjected to oxidation at the expense of oxygen dissolved in water. These processes result in organic substances gradually being mineralized by their disintegration into simpler substances. It must be underlined that a complex of biocenoses formed by different hydrobionts takes part in self-purification processes. The majority of them are also directly involved in decontamination of sea from bacterial contaminants, including pathogenic microbes. The mechanism of antibacterial action of hydrobionts is sufficiently diversified. Some of them absorb bacteria for feeding, others cause the cell lysis, and the third release the antibacterial agents into environment. Different type relationships are formed between the bacterial population and other hydrobionts. The predominant types, besides trophic, are metabiosis and antagonism. The biochemical activity of hydrobionts is a dominant process in self-purification of marine ecosystem. The conclusions are made about the need of monitoring the sea water quality by using the methods of biotesting on animal and plant test-organisms of different trophic levels.