The Results of the Functional State of the Meiobenthic Fauna Research in High-Sulfide Biotopes of Coastal Lakes-Lagoons of the Kandalaksha Bay (White Sea)

Abstract

The article presents the results of the studies of physiological state of meiofauna taken from the bottom sediments of two meromictic lakes which had different stages of geological isolation from the White Sea. It was concluded that active living benthic organisms of these high-sulfide biotopes could penetrate no deeper than the upper boundary of the hemocline. Organisms living at the depth of the upper redox-chemocline boundary (nematodes, chironomids and oligochaetes) in the lakes-lagoons of the Kandalaksha Bay (White sea) have high locomotor activity characteristics. Nematodes and rotifers were found on the lower edge of the chemocline, but they were motionless and did not show signs of active life. Therefore, they, with a high degree of probability, could be attributed to the dead component of the community. No meiobenthos was found in the anoxic zone at the bottom of the sulfide lake at a depth of 7.5 m. Finding abundant motionless benthic ciliates, belonging to the family Tintinnidae at the upper edge of the chemocline of Lake Trekhtsvetnoe does not allow researchers to make unambiguous conclusion about their physiological state. The main factor limiting the penetration of zoobenthic oxybionts into the redox zone of the studied meromictic White Sea lagoons is obviously the combined effect of deficiency of dissolved oxygen with simultaneous contamination of the aquatic environment and benthal with hydrogen sulfide. On the contrary, the positive properties of this habitat can be attributed to the high content of potential food resources (biomass of photo-and chemolithotrophic microorganisms), and, probably, the previously observed layer of the chemocline with an increased temperature. It is noteworthy that the latter phenomenon, which is observed in most of the stratified lakes-lagoons of the polar region, is most developed in the winter period.