SS4.10 Interdisciplinary Contributions to the Maintenance of the Integrity of Aquatic Ecosystems
Date: Tuesday, June 11, 2002
Time: 4:45:00 PM
Location: Colwood
 
Ward-PaigeCA, McMaster University, Hamilton, Canada, wardpaca@mcmaster.ca
Risk, M, J, McMaster University, Hamilton, Canada, riskmj@mcmaster.ca
 
BIOEROSION SURVEYS ON THE FLORIDA REEF TRACT SUGGEST WIDESPREAD LAND-BASED STRESS ON THE REEFS
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Cliona delitrix is a destructive, bright orange overgrowing boring sponge that kills coral. Previous work has shown that it is a sewage bioindicator. Field surveys conducted with the Florida Marine Research Institute in summer 2001 showed that C. delitrix and a closely-related sponge, C. lampa, are widespread and abundant. Colonies of C. delitrix were up to 2m in diameter. Coverage by these sponges was highest near areas of dense human habitation, and lowest in remote areas. Study of archival videos has allowed us to document, at nearshore sites, a 3-fold increase in sponge colony numbers and almost a 10-fold increase in sponge area, from 1996 to 2001. Analysis of stable isotopic ratios of Nitrogen in sponge tissues identifies the importance of terrestrial sources of organic matter. The Florida Reef tract lost 38% of its coral cover between 1996 and 1999, as bioerosion increased. These results suggest that bioerosion estimates are an essential part of any reef monitoring program, and that concerns about global change are overblown, compared with land-based threats.