Recovery of Zostera marina L. thickets in Kandalaksha bay, White Sea

Seagrass Zostera marina forms thickets (meadows) in shallow coastal areas of the Atlantic and Pacific Oceans as well as in other numerous seas of these regions. Zostera is a perennial with a well-developed root system. It plays an important role in the positive development of bioenergy and marine ecosystems of the oceans as a whole. In the 30s of the XX th century, in the North Atlantic Ocean massive destruction of Zostera with subsequent gradual recovery of its meadows was registered. In the 60s of the XX th century, in the White Sea mass death of seagrass was also observed. This phenomenon was frequently encountered on the territory earlier. The death of Zostera was followed by a biological disaster resulting in the violation of trophic links and a chain of negative aftereffects. At the end of the 60th, recovery of the Zostera population was observed in the White Sea. The process of seagrass meadows’ recovery was investigated in the littoral zone of Ryashkov island located in Kandalaksha Bay of the White Sea. The area of thickets was defined annually in June and July for a period of 10 years starting from 1973, further once in three - five years. Thus, the research process of Zostera recovery covers a period of 37 years, and we plan to continue our study. In 1973, only small areas or scattered clumps of seagrass, a total of only 127 m 2, were discovered in the littoral zone of Ryashkov island. In 2009, the total area of Zostera marina meadows reached 5177 m 2. Multidirectional fluctuations of the area with thickets of eelgrass were registered on all eight studied sites starting from 1980. Their occurrence is conditioned by various reasons caused by unequal seasonal and annual variability of environmental conditions (abiotic and biotic) in all eight habitats of the seagrass found on the island. The general tendency of the recovery process in the area of seagrass meadows in the littoral of Ryashkov island is shown.