Characterization of corals communities at Rose Atoll, American Samoa.

Kenyon; Maragos; Cooper

To manage resources and interpret ecosystem changes, reef managers benefit from access to the best available scientific data and analyses. Scientific knowledge of the coral communities at Rose Atoll in the central South Pacific has grown since the first visit by scientists in 1839, as has anthropogenic damage, most notably that from a ship grounding and accompanying chemical release in 1993. Given the challenges of operating in this remote, uninhabited location, marine survey activity since that time largely focused on the areas most heavily impacted by the grounding events. Here, we apply multivariate statistical analyses to data acquired in 2002 and 2004 from several complementary survey methods that operate at different scales of spatial and taxonomic resolution to characterize the coral communities at Rose Atoll in relationship to strata defined by habitat, geographic sector, and depth zone. The southeast sector of the fore reef is distinguished from other fore-reef sectors in several analyses, which likely reflects the response of the benthic biota to prevailing trade-wind-driven seas and large waves arriving from the southeast. The southwest fore-reef sector is also distinguished in several analyses; recovery of corals after injury from the vessel grounding on the southwest arm of the fore reef is documented and the special role of pocilloporids in the recovery is highlighted. Coral diversity at Rose Atoll is low compared to larger high volcanic islands to the west in the Samoan Archipelago but is high compared to adjacent atolls and reef islands to the north and east (Tokelau and southern Line Islands) where data are available. We provide a list of 143 anthozoan and hydrozoan corals observed at Rose Atoll during survey activities since 1994. Our spatially widespread surveys that generate independent metrics of benthic cover and coral abundance collectively provide the most comprehensive description of coral communities at Rose Atoll produced to date, which can serve as an important baseline in assessing the direction and pace of future changes.