Ion fractionation in young sea ice from Kongsfjorden, Svalbard

The fractionation of major sea-water ions, or deviation in their relative concentrations from Standard Mean Ocean Water ratios, has been frequently observed in sea ice. It is generally thought to be associated with precipitation of solid salts at certain eutectic temperatures. The variability found in bulk sea-ice samples indicates that the fractionation of ions depends on the often unknown thermal history of sea ice, which affects the structure of pore networks and fate of solid salts within them. Here we investigate the distribution of ions in Arctic sea ice that is a few weeks old with a reconstructible thermal history. We separate the centrifugable (interconnected) and entrapped (likely disconnected) contributions to the ice salinity and determine their ion fractionation signatures. The results indicate that differential diffusion of ions, rather than eutectic precipitation of cryohydrates, has led to significant ion fractionation. The finding emphasizes the role of coupled diffusive–convective salt transport through complex pore networks in shaping the biogeochemistry of sea ice.

Counts of benthos communities in Kongsfjorden in 2009

In order to reveal the structure of the sparsely known deeper sublittoral hard bottom communities of glacial Kongsfjorden, the macroepibenthos from six depth zones (30-200 m) was analysed. A total of 180 still images derived from 6-h video recorded at the Kongsfjordneset remotely operated vehicle station were assessed quantitatively. Overall 27 mainly suspension-feeding species/taxa were observed. Of these, two-thirds have an arcto-boreal distribution, while the remainder are cosmopolitan. The overall mean epibenthos abundance was 33 ind./m**2 with maximum values at 150 m depth (97.9 ind./m**2). The majority of the taxa inhabited the entire depth range. Encrusting red algae, an unidentified sponge and the sea anemone Urticina eques, characterized the assemblage of the shallow zone. The sea anemones Hormathia spp. were important below 30 m, the Serpulid polychaete Protula tubularia was characteristic for the community below 50 m and the demosponge Haliclona sp. was a key taxon between 100 and 200 m depth. Cluster analysis and non-metrical multidimensional scaling based on abundance data showed differences between the assemblages along the bathymetric gradient, but only in the shallower depths in relation to the substratum surface incline. As surface and tidal current impacts attenuate with increasing depth, there is a gradual trend from robust key species towards more fragile ones (i.e. P. tubularia), in line with the 'Physical control hypothesis'.