Pelagic coelenterates in the Atlantic sector of the Arctic Ocean - species diversity and distribution as water mass indicators

Marginal seas of the Arctic Ocean are well recognized as one of the richest ecosystems in the world's ocean, being at the same time the most vulnerable to climate change. Such vulnerability affects the distribution of water masses, thus influences the pelagic species dispersal and local diversity. For certain reasons some plankton species can be used as indicators of water mass distribution. Although the use of copepods and chaetognaths in such a manner is well documented, still little is known about the potential of pelagic Coelenterata as possible indicator species; they are still poorly investigated in this part of the Arctic Ocean. Therefore, a survey of these gelatinous animals was conducted in a transect between the Norwegian, Greenland, and Barents Seas in summer 2011. A total of 21 taxa were encountered and the most abundant was Aglantha digitale. Species distribution coupled with hydrological analysis of the investigated area enabled us to establish the water mass indicator taxa. Therefore, A. digitale was connected with the Atlantic Water Mass, while Bougainvillia superciliaris and large numbers of ctenophores were correlated with the Arctic Water Mass. The results presented herein may provide the basis for developing new tools to analyze changes in the Arctic Ocean.