abyssorum abyssorum (Koren & Danielssen 1875). As Brotskaya & Zenkevich (1939) mentioned in their benthos research data, only G. m. margaritacea of the above species formed a significant biomass in the Barents Sea in the first half of the 20th century. However, its dense populations were basically concentrated in the central part of the Barents Sea and off the west coast of the Novaya Zemlya archipelago. The proportion of

sipunculans in the total benthic biomass in those areas reached 50%, whereas the mean biomass was 15–65 g m− 2. A second full-scale benthos survey in the Barents Sea undertaken by the Polar Research Institute of Marine Fisheries and Oceanography (PINRO) in 1968–1970 revealed a considerable decrease in the Gephyrea biomass. Its share of the total benthic biomass has decreased tenfold ( Denisenko 2007). Further reductions in the biomass and area of distribution of those species in the central CAL-101 in vivo Barents Sea were discovered during benthic research in the area in 2003 ( Denisenko 2007). Generally, despite Sipuncula being widespread in Arctic bottom communities, Epacadostat chemical structure data on the numbers of species and their role in the Barents Sea’s benthos are quite fragmentary and scanty. The latest similar study of the quantitative distribution of Sipuncula in the Arctic was carried out off the west Spitsbergen

coast (Kędra & Włodarska-Kowalczuk 2008). Until recently, no dedicated research of the quantitative distribution of Sipuncula had been carried out in the Barents Sea as a whole, although in the last few years several publications by one of

the present authors have appeared describing the quantitative distribution of these invertebrates in particular parts of the Barents Sea (Central basin, the Novaya Zemlya archipelago, Franz Josef Land, the Pechora Sea) (Garbul, 2007, Garbul, 2009 and Garbul, 2010). The purpose HDAC inhibitor of this study is to give details of the contemporary diversity of sipunculans and their abundance in the southern and central Barents Sea. Material was collected during a multidisciplinary scientific expedition of PINRO on r/v ‘Romuald Muklevich’ in August–September 2003. samples of macrozoobenthos were taken from 63 benthic stations in central and southern Barents Sea (Figure 1). The data from two research cruises of the Murmansk Marine Biological Institute (MMBI) on the r/v ‘Dalnye Zelentsy’ in 1996 and 1997 were used for analysing the long-term dynamics of Sipuncula densities in the central Barents Sea (Garbul 2010). Primary data from the PINRO cruise on r/v ‘N. Maslov’ in 1968–70 and the literature data from the 2003 cruise of r/v ‘Ivan Petrov’ in the central Barents Sea were used (Denisenko, 2007 and Cochrane et al., 2009). Quantitative samples of macrozoobenthos were taken with a 0.1 m2 van Veen grab in five replicates at each station. The material was washed through a soft 0.5 mm mesh sieve and fixed with 4% formaldehyde buffered by sodium tetraborate.