ABSTRACT: The tissue of 31 demosponge and 7 hexactinellid species was analyzed for its composition of organic and inorganic matter. With one exception (Haliclona cf. gaussiana)inorganic matter, i.e. mostly the siliceous skeleton, accounted for most of the dry weight, varying between about 60 and 95%dry wt. There were no general trends in the ratio of organic to inorganic matter within sponge orders or genera, and within one species, the ratio could vary between stations. For one of the hexactinellids, Bathydorus spinosus, several size classes were analyzed and there was no systematic change in the organic:inorganic matter ratio with specimen size. For some species the results from the Weddell Sea sponges are in good agreement with earlier data from McMurdo Sound. The low organic matter content in Weddell Sea sponges implies that sponge biomasses are much lower than hitherto assumed on the basis of their high abundances and large sizes. In consequence, Antarctic sponges, despite their ubiquitousness, may only channel a minor fraction of the general bentho-pelagic flow of matter and energy, and their main role in the ecosystem is likely structural rather than dynamic.

KEY WORDS: Sponges . Antarctica . Tissue composition . Demosponges . Hexactinellids . Inorganic skeleton

Published in MEPS Vol. 123 (1995) on July 20
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1995