MEPS 147:63-75 (1997)  -  doi:10.3354/meps147063

The epibenthic megafauna of the high-Arctic Laptev Sea shelf was investigated in August/September 1993 and October 1995. At 13 stations in water depths of between 14 and 45 m, series of 5 to 29 photographs, each depicting about 1 m² of the seabed, were taken to assess epifaunal distribution patterns and abundances. Furthermore, population biomass of dominant brittle stars was estimated by combining abundance values with size-mass relationships and size frequencies established by measuring specimens on scaled photographs. A total of 13 epibenthic species were identified. Species numbers per station were low, ranging between 1 and 6. Total epibenthic abundances, averaging 173.7 ind. m^-2, ranged considerably between 0.1 and 579.5 ind. m^-2. Except for some stations on shallow shelf banks <20 m that were characterized by bottom-water salinities <30 due to fluvial dilution, the brittle star Ophiocten sericeum dominated the megabenthic shelf assemblages. At the flanks of sunken Pleistocene river valleys in depths >30 m, it reached maximum density and biomass values of 566 ind. m^-2 and 1.5 g ash-free dry mass (AFDM) m^-2, respectively. At some sites, the brittle star Ophiura sarsi occurred in abundances of up to 35 ind. m^-2 and attained a biomass of 3.8 g AFDM m^-2. Of local importance were the sea cucumber Myriotrochus rinckii (up to 70 ind. m^-2) and the bivalve Arctinula greenlandica (up to 33 ind. m^-2). All other species were recorded with distinctly lower densities (<=1 ind. m^-2). Gross estimates of population respiration and production of dominant brittle stars suggest that their organic carbon demand may amount to a pooled average of about 4 mg C m^-2 d^-1 in the Laptev Sea, locally even to a maximum of >10 mg C m^-2 d^-1. This finding indicates that a substantial portion of the energy flow in this high-Arctic shelf ecosystem may be channelled through dense brittle star assemblages.

Benthos · Arctic · Laptev Sea · Abundance · Biomass · Carbon demand