Coral Cover of Diaseris distorta and Porites sverdrupi at Isla Catalana, Gulf of California

Coral Cover of Diaseris distorta and Porites sverdrupi at Isla Catalana, Gulf of California

Diaseris distorta is a free-living, solitary fungiid coral that mostly inhabits sand or mud habitats surrounding coral reefs. It is distributed throughout the tropical waters of the Red Sea, Indian Ocean, and Pacific Ocean. Data on this species‘ population densityand surface area was collected at its northern-most limit of distribution in the Eastern Pacific off the coast of Isla Catalana in the Gulf of California. Thirty randomly located 0.25m2 photo quadrats (7.5m2 total area) were analyzed using CPCe software. The mean surface area of Diaseris distorta was 1.6cm2 ± 0.4 s.d. per individual, and the mean number of individuals per quadrat (0.25m2) was 15.2 ± 5.7 s.d. Live coral cover ranged from 0.003-0.020%, much less than those measured elsewhere (e.g. 100% cover in Galapagos and other sites in the Gulf of California). A possible explanation for low cover is that this population occurs at the northern-most limit of its known distribution in the Eastern Pacific where environmental conditions may be marginal for growth. Three colonies of the rare, endemic, branching coral Porites sverdrupi were also observed during the survey with a mean surface area of 3.8cm2 per colony and a mean diameter of 1.2cm. This is much smaller than colonies reported from other locations further south (2.5 to 9.3cm), again suggesting marginal growth conditions. Additional research on these two species of coral will allow comparisons with future surveys of these populations and those in other regions, providing valuable information to sanctuary managers.