Таксоцен моллюсков рыхлых грунтов прибрежной зоны северо-восточного сектора Черного моря в начале XXI в.

Abstract

In the context of increasing climatic and anthropogenic changes, one of the most pressing problems of modern ecology is the study of the formation of the response of marine ecosystems: structural rearrangements of communities, changes in trophic interactions and adaptation of species to changing environmental conditions. At the same time, not all changes occurring in marine shelf ecosystems can be explained by the action of external factors, since the dynamics of ecosystems associated with the action of internal processes, such as natural successions, are known fragmentarily. Bottom communities play a leading role in the functioning of ecosystems, modifying the habitat, influencing nutrient cycling and primary productivity; bottom ecosystems are associated with the possibility of carbon immobilization and sequestration, the assessment of which remains a fundamental scientific problem. Coastal communities of the Black Sea are a convenient model for this type of research. Here, the dominant positions in the benthos are occupied by carbonate-forming mollusks, and it is this zone at the end of the 20th beginning of the 21st centuries underwent the greatest changes. The main goal of this work was to study the patterns of dynamics of abundance and population structure of mollusks in soft bottom communities of the coastal zone of the North Caucasus coast of the Black Sea in 2015–2022. During the annual expeditions of the Shirshov Institute of Oceanology RAS, samples were collected from two depths (10 and 25 m) and the structure of the taxocene of mollusks and the dynamics of the size structure of the main dominants were analyzed. It is shown that as a result of the constant replenishment of bivalve populations and a decrease in the pressure of rapana and jellyfish in 2015–2022 abiotic factors and cyclic processes occurring in populations came to the fore. The main dominants in the taxocene of Bivalvia in the northern Caucasus in 2015–2022 were at the 10 m isobath Chamelea gallina and Lucinella divaricata and at the 25 m isobath Gouldia minima and Pitar rudis. Despite the successful almost annual recruitment and multimodal appearance of the size-frequency diagrams of these species, stabilization of populations was not observed. Fluctuations in the abundance of these species reached an order of magnitude. The highest taxocene biomass was recorded in 2020 at the peak of the dry and warm-water period. Based on the analysis of size-frequency diagrams, an attempt was made to estimate the maximum average age of individuals of these species.

Keywords: Black Sea, bivalves, macrozoobenthos, population dynamics