Health status of the coral communities of the northern Galapagos Islands Darwin, Wolf and Marchena

Spatially reduced distributions of Galapagos corals and fragmented habitat, after recent strong El Niño Southern Oscillation events and greatly increased levels of human visitation, fisheries activities and dive tourism, raise important conservation questions as to the effects of compounding stress upon coral communities. A lack of knowledge concerning zooxanthellate coral disease in the Galapagos Marine Reserve, which could be used as an indicator of natural and/or anthropogenic stress prompted this characterisation of Galapagos coral health abnormalities. Colony condition was evaluated during research cruises conducted in September 2005, May 2006 and March 2007 at the northern islands of Wolf and Darwin, and in the north-central archipelago at Marchena. Observations of coral health and associated biota were taken for different coral species and sites, allowing characterisation of health anomalies that may indicate disease. Frequency of occurrence (FOC: the proportion of sites exhibiting a particular symptom) across sites and prevalence (the proportion of colonies presenting symptoms) were determined for six species-specific and three general anomalous health states. Over the eight coral reef communities sampled, the overall prevalence was 23.9 % (n = 973). The massive coral Porites lobata was found to be most affected, with 35 % showing symptoms of parasitism or illness. The most common health anomaly was identified as Porites trematodiasis, with 32 % overall prevalence within sites and found in all surveyed sites (FOC = 100 %)