Thursday, September 13, 2007

Biological monitoring

Video transect surveys and urchin counts were performed today by Hugh Small, Camilo Trench, and myself. Fifteen video transects were run (16 m length transect line). All urchins within 0.5 m on either side of the transect line were identified and counted. A total of 20 urchin count transects were run (16 square meters per transect). Diadema antillarum is locally abundant near the ICON site and was the most abundant urchin surveyed. This is very encouraging as algal biomass is significantly reduced around the grazing area of individuals and where D. antillarum is absent, algal biomass is incredible (thats a scientific term).

I noted several large Acropora palmata pieces (up to 1 m in max. diameter) that had been broken and transported behind the reef crest during Hurricane Dean. Other than this, there were no indications of any negative hurricane impacts.

Nineteen colonies of Montastraea faveolata were tagged and photographed. Photos should be re-taken in 3 months to assess mortality and recovery. YBD appears to only be affecting a small proportion of M. faveolata colonies, but diseased colonies appear to have a clumped distribution. Colonies were tagged because YBD seems to be occurring throughout the Caribbean at the present time. I have received confirmed reports of YBD in the Dominican Republic and U.S. Virgin Islands to date. YBD appears to have been more abundant at the St. Croix site.

I would like to extend my utmost gratitude for the field support provided by Hugh and Camilo and to our captain Anthony.

Best regards,
Derek Manzello