The sponge association of the abyssal Norwegian Greenland Sea: Species composition, substrate relationships and distribution

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Abstract
During the ‘Meteor’ Expedition 13 in July and August 1990 to the northern part of the Norwegian Sea off west Spitsbergen, 7 stations with a depth of 2000 m or more were sampled with Agassiz trawl or hyperbenthos sledge, 14 more with a large box corer. Sponges were found at 6 of the trawl stations and in 2 box cores. A total of 19 species occurred, most of which were new to the area. Eight of the species were encountered more often than the other 11. Literature review and check of unpublished samples showed that by distribution, frequency of occurrence or abundance these species can be defined as the typical sponge association of the Norwegian and Greenland abyssal sea. This sponge association has a wide occurrence over the deep Norwegian-Greenland seas and parts of the Arctic basins. The analysis of substrate utilization of the 8 core species shows that all of them are able to colonize soft bottom, even some that previously had been considered to be dependent on hard substrate exclusively. Alternative substrate utilization and, in some species, the adoption of an infaunallife style are judged to be major reasons for the success of these species in the deep sea. The infaunal life style of the species Thenea abyssorum, Trichostemma sol and Tentorium semisuberites is documented and population structure data are given for the first time.