Distribution and structure of macrobenthic fauna in the eastern Laptev Sea in relation to environmental factors

The Laptev Sea still ranks among the less known regions of the world’s ocean. Here, we describe the distribution and composition of macrobenthic communities of the eastern shelf and identify key environmental control factors. Samples were collected from dredge catches carried out at 11 stations at depths between 17 and 44 m in August/September 1993 during the TRANSDRIFT I cruise of the Russian R/V “Ivan Kireev.” A total of 265 species were identified from the samples, mostly crustaceans (94). Species numbers per station ranged from 30 to 104. Macrobenthic community distribution clearly showed a depth zonation, consisting of a “Shallow” zone (<20 m), dominated by the crustaceans Mysis oculata (Mysidacea) and Saduria entomon (Isopoda) as well as molluscs, an “Intermediate” zone (20–30 m), characterised by a clear dominance of the bivalve Portlandia arctica, and a “Deep” zone (>30 m) with bivalves P. arctica and Nuculoma bellotii as well as brittle stars Ophiocten sericeum and Ophiura sarsi being most abundant. According to a correlation analysis between faunal and environmental data a combination of duration of ice cover and water depth, respectively, showed the highest affinity to macrobenthic distribution. We conclude that the food input to the benthos, which is largely related to ice-cover regime, and the stress due to the pronounced seasonal salinity variability, which is primarily related to water depth, are prime determinants of macrobenthic community distribution and major causes of the prominent depth zonation in the Laptev Sea. Within the depth zones, sediment composition seems to be most significant in controlling the patterns in the distribution of the benthic fauna.