Present geoecological transformations in the Kerch strait ecosystem

This study examined the distribution, structure, and dynamics of bottom communities of macrozoobenthos in the Kerch Strait based on an analysis of literature sources from 1934 and 1955, archival data documenting hydrobiological field investigations of the Southern Research Institute of Marine Fishery and Oceanography (YugNIRO, Kerch) in 1986 and 1989, and results of the joint Russian-Ukrainian benthic survey of the Kerch Strait (47 stations) conducted by the Institute of Geography of RAS and YugNIRO in the summer of 2010. It was found that populations of filter-seston feeding bivalves in the strait ecosystem have degraded over the past 75 years, whereas populations of detritus-feeding polychaetes preferring muddy bottoms have become much more abundant. Researchers identified species of bottom animals and strait areas exhibiting maximum changes. An analysis of the dynamics of bottom sediment structure in the strait based on YugNIRO archival data and the results of a 2008 diving survey conducted by the Institute of Geography of RAS (49 divers) demonstrated that the observed transformations are associated with silting of a considerable part of the strait bottom as a result of both earlier and more recent economic activities, particularly the disposal of dredging grounds from 1960 to 1990 and the construction of the Tuzla Dam in 2003, respectively. However, the character of the fixed transformations does not enable us to identify the specified reasons as the sole causes of the changes; therefore, the authors also consider hypotheses explaining other mechanisms. The authors conclude that further research on geoecological dynamics of the Kerch Strait ecosystem is needed, particularly after the construction of the Crimean Bridge.