ESTABLISHING REFERENCE POINTS TO ASSESS LONG-TERM CHANGE IN ZOOXANTHELLATE CORAL COMMUNITIES OF THE NORTHERN GALAPAGOS CORAL REEFS

SUMMARY Dramatic reduction in zooxanthellate corals through bleaching during the 1982–3 El Nino event and subsequent bioerosion have resulted in archipelago-wide loss and fragmentation of coral habitat. Slow natural recovery and the risk to corals from global climate change raise important coral conservation questions in a multi-use reserve. The largest coral reef communities remaining at Wolf, Darwin and Marchena islands were surveyed, to provide information on the conditionof these last persisting reef systems as a basis for future evaluation of the effects of climate change, human use and management upon them. Over the period September 2005 to February 2007, 2250 m of subtidal habitat were surveyed at 15 m and 6 m depth at four study sites. At each site we recorded substrate heterogeneity, zooxanthellate coral diversity and relative abundance, simple measurements of colony size, reef relief and health, and relative abundances and size distributions of the associated subtidal marine community (sessile macroinvertebrates and algae, mobile macro-invertebrates and reef fish). Given the high level of tourism visitation, restricted range of the coral reef, considerable small scale between-site differences in coral species composition and associated subtidal assemblages, high subtidal species diversity unique to the northerly islands, and strong frequent climatic stress, appropriate additional protective measures, such as low impact fixed moorings, are recommended. Such measures will help conserve the ecosystem function of these key habitat-forming species both in the north and for the archipelago as a whole. RESUMEN