On the ecophysiology of the sponge Halichondria panicea in Kiel Bight. I. Substrate specificity, growth and reproduction

Abstract

Between December 1983 and Apnl 1985 field expenments and laboratory observations on Hahchondr~a panicea were performed In the Hausgarten area at Boknis Eck k e l Bight The sponge populahon was sampled regularly by dredging and scuba diving Field growth expenments were conducted at the same hme Phyllophora sp and Phycodrys sp were the preferred substrate algae while Delessena sanguinea and fllamentous f ~ n e algae served as substrate only occas~onally A vanety of inorganic and organic hard substrates was also found to be accepted by sponges Growth of H panlcea was observed between March and July Growth rates seemed strongly dependent on temperature, less correlated wlth food avallabdity The most vigorous growth occurred in May and June Aftel July a strong dechne In mean w e ~ g h t of the ~ndividually marked specimens resulted in negative growth rates until the end of September Dunng late fall and winter no changes in mean i n d ~ v ~ d u a l weight were observed Constderable changes in biochemical composition (condition index and protein lipid and glycogen content) and appearance of young colonies of H panicea in early fall ~ n d ~ c a t e that the maln reproductive actlvity occurs In August and September As this is the t~ rne of greatest weight loss in adults it can be inferred that adult H panlcea degenerate and disintegrate after reproduchon