Project Summary for 2006-12A: Ecology of sponges on Florida reefs: Demography and bleaching.
The Caribbean barrel sponge, Xestospongia muta, is a large and common member of the Florida coral reef community at depths greater than 10 m, and has been called the "redwood of the deep". Despite its prominence, high biomass and importance to habitat complexity and reef health, very little is know about the basic biology of this massive sponge, including rates of mortality and recruitment, reproduction, growth and age. Like reef corals, this sponge is subject to bleaching and subsequent mortality. Additional threats to this species include fishing line debris, which can cleanly slice through sponges during storm events and in high-flow environments.
The PI requests facilities support as dayboat, technical diving, and laboratory use at the Key Largo NURP/UNCW, and a small amount of salary and travel funds to continue long-term studies of X. muta, begin long-term studies of two additional reef sponge species, add a new deep-water transect site, and continue NSF co-sponsored investigations of the chemical ecology of Caribbean sponges. With past support, the PI and his students have established and monitored 12 permanent circular transects (16 m diameter) containing over 625 marked X. muta to document sponge mortality, recruitment, bleaching, growth, and damage by debris. Past awards to this program have been remarkably productive, resulting in 11 peer-reviewed publications since 2002. Studies of sponge chemical ecology have resulted in a revision of our understanding of Caribbean reef ecosystems and the isolation and identification of bioactive metabolites involved in antipredatory and allelopathic interactions. Based on the results to date, the following objectives are proposed for the next two years of research:
Coral reefs are generally perceived to be in decline around the world, with a variety of possible explanations. Bleaching of reef corals may be a consequence of steadily rising sea temperatures due to global climate change; this proposal will test this hypothesis and an alternative (reproductive stress) for bleaching of a coral reef sponge. Alternative hypotheses for loss of coral cover include those of "indirect effects": loss of spongivorous reef fishes may alter the ecology of reef sponges to permit the growth of otherwise cryptic species, some of which may more effectively compete for space with corals. The proposed study will advance our understanding of the complex relationships between benthic invertebrates, their predators and their competitors in coral reef environments.
Outreach & Education: The PI educates and trains undergraduate and graduate students, including underrepresented groups, in marine science, and the budget for this proposal includes salary support for a MS student in the PI's research program. The PI has a public outreach website that describes the results of the barrel sponge monitoring program, sponge bleaching, disease, and damage from fishing debris.
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