Coral and fish community structure and reef structure across Heron Island reef, southern Great Barrier Reef

Brief description

In 1977, a 2.3 km long transect was established across Heron Island reef in the southern Great Barrier Reef. The transect was located about 1 km to the east of the island, passing from the sheltered south-western reef crest across the reef flat and shallow lagoon in a northerly direction to the exposed northern reef crest. Forty-five sites were located at 50 m intervals along the transect. The levels of sites relative to each other were measured to provide an index of wave energy integrated through time. Sites were grouped into zones based on these levels (South Crest, South Outer Reef Flat, South Inner Reef Flat, Lagoon, Pocillopora Zone, North Inner Reef Flat, North Outer Reef Flat and North Crest).Three replicate 10 m line transects, were surveyed at each of the 45 sites. The transects were placed at right angles to the main transect, with each transect beginning where the previous 10 m transect finished. At 20 cm intervals along each transect, the dominant substrate structural type inside a 10 cm circle around each sampling point was recorded. Nine structural types were used: 5 living coral types (massive and submassive; thin, medium and thick ramose) and 4-non-living types (sand, rubble, consolidated and pavement).At each of the 45 sites, coral communities were sampled along 3 replicate 20 m line transects, laid out as described above. At 20 cm intervals along each transect, the dominant coral species found inside a 10 cm circle around the sampling point was recorded. When no macroscopic species occupied the circle, a bare space was recorded.The fish communities at 9 sites, which were representative of the major zones along the transect, were sampled. Paired samples were collected at each of these sites by staking out 2 mm mesh nets to surround an area of 21.5 m². The enclosed area was then poisoned and the fish were collected by hand nets until the area was exhausted. Fish were identified to species level where possible. This study was undertaken to investigate changes in the structure of a coral reef ecosystem along a gradient of wave energy. The three components of the study were:(1) to describe the topographic structure of the substrate, a major abiotic component of the system in relation to the gradient(2) to describe the community structure of the corals, the main architectural components of the reef in relation to the gradient and also to the reef structure(3) to describe the community structure of the fish, another major biotic component of the system in relation to the gradient, the reef structure and coral community structure.The coral data were also used to examine spatial patterns in the occurrence of corals and interactions and aggression between corals.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: Zones and approximate span of sites defined along the transect:SC = South Crest (Site 1)SORF = South Outer Reef Flat (Sites 2-6)SIRF = South Inner Reef Flat (Sites 7-12)L = Lagoon (Sites 13-25)PZ = Pocillopora zone (Sites 26-30)NIRF = North Inner Reef Flat (Sites 31-38)NORF = North Outer Reef Flat (Sites 39-43)NC = North Crest (44-45)Substrate types found in the study area:LivingMassive - Unbranched coral colonies with rounded regular surfacesSubmassive - Unbranched coral colonies with irregular surfaces or protuberancesThin ramose - Branched coral colonies with main branches 10 mm thickMedium ramose - Branched coral colonies with main branches 10-20 mm thickThick ramose - Branched coral colonies with main branches >20 mm thickNon-livingSand - Unconsolidated coral sandRubble - Unconsolidated coral fragmentsConsolidated - Consolidated rubble and sandPavement - Smooth consolidated surface often with thin layer of fine sand on top

Notes

Credit
Bradbury, Roger H, Dr (Principal Investigator)