Rapid Ecological Assessment (REA) of coral biodiversity and reef health in Manus and New Ireland Provinces, northern Bismarck Sea, Papua New Guinea

Fringing reefs at 19 locations in the Tigak Islands and 17 locations around Manus Island in the northern Bismarck Sea, Papua New Guinea were surveyed in August/September 2006. Locations were selected to provide the broadest range of reef habitat types. At each location, two sites were surveyed (deep: >10m and shallow: <10). Deep sites were surveyed first, with the observer swimming initially to the maximum survey depth (maximum of 40-45m), then working steadily into shallower waters. Observations at each site were made over sections of reef of approximately 5000m² in total (50x100m).

An inventory of species, genera and families of sessile benthic taxa was compiled for each site. The inventory included hard corals, soft corals, zoanthids, sponges, macro-algae and other sessile macro-benthos. At the end of each survey, the inventory was reviewed and each taxon was categorized in terms of its relative abundance in the community.

For each hard coral taxon present, a visual estimate of the total amount of injury (dead surface area) present on colonies at each site was made in increments of 0.1, where 0 = no injury and 1 = all colonies dead. In addition, for each taxon, the proportion of colonies in each of three size classes (up to 10cm, 10 to 50cm and greater than 50cm colony diameter) was recorded.

When identification of hard coral species was not possible, notes and photographs were taken and, if necessary, small samples were collected for later examination. Most specimens were lodged with the local TNC Office for use as a reference collection. Some coral samples were taken to Australia to compare with reference collections in the Museum of Tropical Queensland and the Australian Institute of Marine Science.

At the end of each survey, site attributes were recorded based on an assessment integrated over the length of the survey. Attributes included percentage cover of major benthic groups and substrate types, biogenic reef development, exposure to wave energy, depth range, angle of the reef slope, visibility (m) and the presence of any unique or outstanding biological features or evidence of impacts.