Thirty Years of the Biomass Dynamics of Several Species in the Intertidal Communities of Two Small Bights of Kandalaksha Bay, White Sea

Abstract

Intertidal benthos monitoring has been conducted annually in two small bights of Kandalaksha Bay from the spring of 1987 up to the present. The observations covered all hydrological seasons (spring, summer, autumn, and winter) and were carried out at standard sites arranged in two transects, from the lower to the middle or higher intertidal level. Standardized methods of sampling and material processing were used within the entire study period. The long-term biomass dynamics of seven main species was analyzed using eigenvector filtering analysis and the dynamic phase portrait method. During the observation period, the structure of the communities studied varied over time, exhibiting trends in either biomass growth for some species or its decrease for others. A weak correlation was found between the main trends in the biomass dynamics of particular species and the main trend in change in the surface water layer temperature in summer in Chupa Inlet. Moreover, the community structure changed from time to time due to anomalous ice melting conditions in one of the explored bights. The analysis of other measured temporal variables allowed us to find out quasi-cyclic biomass changes in all species studied. The duration of the quasi-cycle varied for different species; in most cases, they were about 4–6 years. Along with that, quasi-cycles within the same species were asynchronous in different bights and even at different intertidal levels of one bight. They did not correlate with either the summer temperature or the quasi-cyclic salinity dynamics in the surface water layer. This allowed us to suggest that the described quasi-cycles were not induced by external factors, but represented self-oscillation processes.