Results of the Territorial Coral Reef Monitoring Program of American Samoa 2006-2012

Fenner, Douglas

Benthic cover of corals, coralline algae, and turf all vary greatly from one site to another around Tutuila. Coral cover averaged 36%. Mean coral cover has increased from 25.5% in 2005 to 36.3% in 2012. Crustose coralline algae is now the second largest cover category, followed by turf. The north side of Tutuila has higher coral cover than the south side, the south side has more crustose calcareous algae (as reported in previous annual monitoring reports), and the north has more turf than the south side. American Samoa reef slopes have higher coral cover than many other places presently, including the entire Pacific, and the South Pacific. However, it has lower coral cover than the Caribbean had in 1977, the Pacific had in 1980, and two visual estimates of coral cover in American Samoa before the crown-of-thorns outbreak in 1978. It is, however, similar to some averages for near-pristine reefs now. American Samoa has coral cover measured by towboard that is as high or higher than the near-pristine areas of the Marianas and Hawaii, but less than the US Pacific remote islands. It is also much more than the latest report from the Great Barrier Reef, which reports cover now of only about 10%. The percentage of all corals in American Samoa which are dead is much lower than all other available comparison areas, and is steady. About 75% of the reef area is covered by calcifying organisms (which is very high) and shows no trends. At individual sites, coral cover has been steady at four sites, has increased at five sites, and decreased at only one site. The site that decreased is Vatia, which was badly damaged by the tsunami of 2009 and Hurricane Wilma in early 2010. As reported before, encrusting corals dominate the reef slopes with columnar corals second most common. Acropora is the genus that is most speciose, though Montipora covers the largest area. Montipora grisea is the coral species that covers the largest area, followed by Porites rus and Pavona varians. A size distribution of the table coral, Acropora hyacinthus, was produced, and it has a peak at the second smallest size category, 10-19 cm diameter. The sponge, Stylissa sp., was the most common invertebrate recorded, followed by another sponge, Dysidea sp