Chamelea gallina in the coastal waters of the Anapa bay bar (the Black Sea) as a carbonate sediment producer

Kosyan A.R^a., Divinsky B.V^b

^aSevertsov Institute of Ecology and Evolution RAS, Moscow, Russia

^bShirshov Institute  of Oceanology RAS, Moscow, Russia

The paper presents preliminary results of monitoring the population of the bivalveChamelea gallina, which is the main source of biogenic carbonates for the Anapa bay bar beaches(the Black Sea). It is shown that by 2017, the biomass of the clams decreased more than twicecompared to 2010, but began to increase in 2018. The average sizes of C. gallina are clearlydivided in terms “year” — “section” — “age”. At the same time, interannual variations of theaverage size are very strong in all age groups. The average shell length of C. gallina significantlyincreased in 2018 compared to 2016, and especially — to 2017. This may be caused by thepopulation decline of the predator Rapana venosa feeding on clams. Geographic differences inthe shell length between sections are not directly related to the distribution of biogenic elements(nitrogen and phosphorus). The differences in longevity and shell size between C. gallina fromtheAnapa region and distant populations from the other parts of the distribution area are likelyrelated to its significant negative correlation with the growth rate, which in turn negativelycorrelates with latitude.

https://doi.org/10.1016/j.oceano.2019.04.003

Modern state and dynamics of the Sea of Azov coasts
Ruben D. Kosyan, Marina V. Krylenko
Shirshov lnstitute of Oceanology, Russian Academy of Sciences (Southem Branch), Gelendzhik, Prostotnaya  lg, 353467, Russia

Abstract
Results: of the modern state researches of the Sea of Azov coasts and coastal processes influencing their evolution are presented. А multidisciplinary study of coastal processes allowed us to identify main types of coast evolution: abrasion, accumulation, and stability. Predominance of abrasion is the main feature of modern dynamics of the Azov shores. Not only the parent rock shores are subjected to erosion, but also accumulative forms are eroded. The eastern coast of the sea retreats most rapidly. The intensity of the abrasion and landslide processes is due to the weak resistance of the rocks composing the coast to the wave forcing. ln particular, intense abrasion occurs in those parts of the coast where wave forcing is strong together with the surges caused Ьу onshore winds, while the beaches are narrow or completely absent. At the same time, the percentage of beach­ forming fractions in eroded soils is low, and the major part of the abrasion materiaJ in the form of suspended matter is transported to the edeep parts of the sea. ln general, the state and dynamics of the Azov coasts are influenced Ьу abrasion-accumulative processes, sea level fluctuations, changes in the wind-wave regime parameters, and fluctuations in the Ьiogenic beach-forming material volumes. The Ьiogenic factor is the most important in the balance of deposits of accumulation forms (spits and bay-bars). Anthropogenic activity also affects the current state of the shores. The transport of beach-forming alluvial sediments into the sea is reduced because of the regulated river discharge. The natural evolution of onshore processes is disrupted during the development of the coast: agricultural activities, industrial and  resort construction, removal of sand and shell material, construction of shore protection facilities.

Spectral structure of surface waves and its influence on sediment dynamics
Boris V. Divinsky, Ruben D.Kosyan
Shirshov Institute  of Oceanology RAS, Moscow, Russia

Abstract
Analysis of the influence of wave energy frequency distribution on the dynamics of suspension over the sea-bottom is the main objective of this study. We revealed the differences between  the  response of  the  eroded sea-bottom to  external  disturbances represented by irregular  surface waves with  permanent integral  characteristics (significant wave height and frequency of the spectrum peak) and variable frequency of the wave energy distribution.