THE 30-YEAR LONG BIOMASS DYNAMICS OF SEVERAL SPECIES IN THE INTERTIDAL COMMUNITIES OF TWO SMALL BIGHTS IN THE KANDALAKSHA BAY, WHITE SEA

摘要

Intertidal benthos monitoring was conducted in two small bights of the Kandalaksha Bay annually since the spring of 1987 up to the present. The observations included all hydrological seasons (spring, summer, autumn, and winter) and were carried out at fixed sites arranged in two transects, from the lower to the middle or higher intertidal level. During the whole period of observation, standardized methods of sampling and material processing were used. The long-term biomass dynamics of seven main species was explored using both eigenvector filtering analysis and dynamic phase portrait method. During the observation period, the structure of the study communities varied in time, showing trends in either biomass growth in some species or its decrease in some others. A weak correlation was revealed between the main trends in certain species' biomass dynamics and the main trend in summer temperature change in the surface water layer of Chupa Bay. Moreover, in one of the explored bights, the community structure change appeared due to anomalous ice melting conditions. An analysis of other known temporal variables allowed us to find out quasi-cyclic biomass changes in all species studied. The quasi-cycle durations varied for different species, but mostly they were close to 4-6 years. Besides this, quasi-cycles within the same species were asynchronous in different bights and even at different intertidal levels of one bight. They correlated with neither summer temperature nor salinity quasicyclic dynamics in the surface water layer. This allows us to suggest that the described quasi-cycles were not induced by external factors, but represented self-oscillation processes.