CS12 Coral Reefs
Date: Wednesday, June 12, 2002
Time: 4:00:00 PM
Location: Colwood
 
RiskMJ, McMaster University, Hamilton ON, Canada, riskmj@mcmaster.ca
 
ESTIMATING SEWAGE AND SEDIMENT STRESS ON REEFS
image
The impact on coral reefs of land-based sources of sewage and sediment are widespread, pervasive, and continue unabated. At the same time, concerns about 'global change' are overblown. A major problem is that most of the world's coral reefs have inadequate baseline data. I describe a method for estimating land-based impacts in areas with no pre-existing data, by using techniques that have been in the literature for decades: sediment stress estimation by insoluble residues, and sewage stress by stable isotopes of nitrogen in coral tissue. I sampled three reef sites on Sulawesi, Indonesia: 1. Bawulu, a relatively non-impacted 'control'; 2. Kendari, near a city and presumed sewage stressed; 3. Pulau Mapara, a remote area where the watershed had been clearcut, leading to massive sediment stress. By plotting % insoluble residues against the N stable isotope ratios, a clear and highly significant separation was obtained among all three sites, allowing estimation of relative impacts of sewage and siltation. Baseline data cannot be produced for all the world's reefs, so we will have to adopt these or similar techniques to aid policy formulation.