Coral communities at Scott Reef and Rowley Shoals, Western Australia

Brief description

In August/September 1993, surveys of coral community composition and structure were carried out at Scott Reefs (North Scott Reef and South Scott Reef) and two reefs in the Rowley Shoals group (Mermaid Reef and Clerke Reef).Coral communities were surveyed at a total of 94 sites, using a semi-quantitative visual survey method and a subset of these sites were surveyed using a video belt transect technique. Sites were areas of around 100-300 m², arranged along cross-reef profiles on the reef flats in a depth range of 0.5-2 m and on the slopes or adjacent reef floor at 4-6 m and 8-12 m. Aerial photography was used to assist in selection of study areas.During each visual survey a detailed list of coral species was made and the relative abundance of each taxa, as a percentage of total macro-benthos, was estimated. The site descriptors recorded were maximum and minimum depth (measured); and subjective estimates of the following: slope; percentage cover of hard substrate; percentage cover of major benthic groups (hard coral, soft coral, macro algae and sponge); percentage cover of substratum categories (platform; large blocks; small blocks; rubble; gravel; sand). An additional 4 sites were surveyed, without recording detailed species lists.A Sony Hi 8 video camera was used to film five replicate 20 m long belt transects about 40 cm wide, within each of the 3 depth ranges, in a sub-set of the sites used for visual surveys. Estimates of percent cover of hard coral, soft coral, algae and bare substratum were made using point sampling of the video tape. At 25 regularly spaced pauses along each video tape, the identity of each item under five points marked on the screen of the TV monitor (one near each corner and one in the centre) was recorded. Percent cover estimates were used to estimate the heterogeneity of the bottom cover as a basis for designing an appropriate sample protocol for a future monitoring program. The visual surveys were carried out to determine whether recognisable, taxonomically consistent assemblages of coral species occurred at the shallow water study sites and to determine the approximate spatial extent of these corals. The surveys were also used to provide detailed taxonomic descriptions of the coral communities at the sites where the video transects were recorded. These surveys were the first quantitative assessments of coral community structure on northwest Australian offshore reefs, previous coral surveys being largely concerned with taxonomic and biogeographic problems.The information collected during this survey formed the basis of of site selection for the subsequent long-term monitoring project.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: The method used for semi-quantitative visual surveys is described in:Done TJ (1982) Patterns in the distribution of coral communities across the central Great Barrier Reef. Coral Reefs 1: 95-107.Relative abundance categories used in visual surveys:0: not seen1: 1-5%2: 6-10%3: 11-30%4: 30-80%5: >80%Abundance units: % of total corals, sponges and macroalgaeThe optimal number of points to sample from video belt transects was determined following procedures described in:Carleton JH and Done TJ (1995) Quantitative video sampling of coral reef benthos: large scale application. Coral Reefs 14: 35-46.

Notes

Credit
Done, Terence J (Terry), Dr (Principal Investigator)