ECOLOGY OF SEAGRASSES OF THE GENUS EELGRASS (ZOSTERA)

Abstract

The Dnieper-Karkinit coastal region of the Black Sea is characterized by the distribution of secondary shallow bays (Yagorlytska, Tendra, Dzharylgach, Karkinit, etc.), which are significantly separated by accumulative forms from the open waters of this sea. The characteristic feature of the listed bays is the formation in the coastal zone of specific landforms such as phytogenic beaches and cliffs, which are composed of dead remains of the seagrass of the genus Zostera (Zostera). It is established that the corresponding phytogenic formations act as «catalysts» of accumulation of sediments of the non-wave field (silt, clay) in the coastal zone. During many years of field researches of the coastal zones of these bays, a steady trend towards their siltation and a simultaneous increase in the number of seagrasses remnants have been identified. This process is extremely dangerous because it changes the basics of functioning of aquatic biogeocenoses, affecting both animals and plant organisms. Accordingly, the accumulation of seagrass remnants causes the evolution of the gulfs of the region. The reasons for the increase in the number of seagrasses remnants of the genus Zoostera on the bays’ coast of the Dnieper-Karkinit coastal area of the Black Sea have not yet been established. That is why there is an objective need to investigate the role of seagrasses of the genus Zostera in the
development of biogeocenoses of coastal waters of different parts of the World ocean and to determine the factors that influence the viability of these seagrasses. Based on the analysis of literature data, it has been established that in modern conditions the seagrasses of the genus Zostera are declining because of the stress of shading, increasing environmental temperature, due to high concentrations of organic substances in water, lack of
oxygen in the water and bottom sediments, due to water pollution by heavy metals and herbicides. However, many species of seagrasses of the genus Zostera (but not all) are able to adapt to existing stress conditions, which is not always favorable to marine ecosystems in general. In particular, the accumulation of heavy metals and herbicides in seagrass tissues may adversely affect organisms of the following trophic levels. Determining the full number of factors that cause mass destruction of seagrasses of the genus Zostera on the bays’ coast of the Dnieper-Karkinit coastal area of the Black Sea requires
further expeditionary studies, which are planned.