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The significance of depth and substratum incline for the structure of a hard bottom sublittoral community in glacial Kongsfjorden (Svalbard, Arctic) - an underwater imagery approach

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Laudien, J. and Orchard, J. B. (2012): The significance of depth and substratum incline for the structure of a hard bottom sublittoral community in glacial Kongsfjorden (Svalbard, Arctic) - an underwater imagery approach , Polar Biology, 35 (7), pp. 1057-1072 .
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Abstract:

In order to reveal the structure of the sparsely known deeper sublittoral hard bottom communities of glacial Kongsfjorden the macroepibenthos from six depth zones (30m - 200m) was analysed. A total 180 still images derived from six hours‘ 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 150m 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 30m, the Serpulid polychaete Protula tubularia was characteristic for the community below 50m, and the demosponge Haliclona sp. was a key taxon between 100m and 200m 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. Protula tubularia), in line with the ‘Physical control hypothesis’.

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