BIOACTIVE SPONGES OUTCOMPETE SCLERACTINIAN CORALS
In recent years there has been an increasing number of reports that sponges are becoming more abundant and in some regions have become the dominating benthic organisms on coral reefs. Some locations in the Caribbean provide increasing evidence that coral reefs are shifting from coral dominated to sponge dominated reefs. For the Indo-Pacific there are also a number of reports which suggest that sponge biomass and abundance are increasingly correlating with a decline in coral cover caused by anthropogenic effects, such as overfishing, sedimentation, eutrophication as well as climate change. One possible mechanism why some sponges are successful competitors is the production of bioactive compounds. It has been well established that sponges use secondary metabolites to defend themselves against predatory fish and invertebrate predators. Studies on sponge allelopathic compounds are however largely lacking. We investigated crude extracts from 10 sponges collected from Bawe Island, Zanzibar, Tanzania to study the antipredatory effects of the sponges and tested also if sponges produced alleopathic compounds to overcome coral competitors. In addition to evaluating various reef sponges in Zanzibar, we investigated in detail the chemical ecology of a particularly dominating sponge (Pseudoceratina sp.), which we first sighted at Koh Phangan in the Gulf of Thailand. This sponge was covering large areas of the benthic substrate and overgrew various other invertebrate species including corals. Results from both the feeding and allelopathic experiments will be presented.
Schupp, P., University of Oldenburg, Germany, firstname.lastname@example.org
Helber, S., ZMT, Germany, Stephanie Helber [email@example.com
Rohde, S., University of Oldenburg, Germany, Sven.firstname.lastname@example.org
Schoenig, E., CoreSea, Thailand, email@example.com
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