Aggressive interactions between corals at different depths at Davies Reef, central Great Barrier Reef

Observations of aggressive interactions between scleractinian corals were made on the southeast side of Davies Reef. In the first survey, conducted at a depth of 10 m, pairs of coral species involved in interactions were identified and the coral sustaining tissue death noted. The minimum distance between the living tissue of each was also measured (the reach). In the second survey, a 3x3 m rope grid, divided into nine 1 m² quadrats was laid on the reef flat at a depth of 1m. In each quadrat the number of interactions involving tissue death of one party was recorded. Coral pairs, positioned close enough to be within interaction reach of one of them were also recorded, including cases where no interaction occurred. The number of coral colonies and visual estimates of coral cover in each quadrat were also recorded. This procedure was repeated at 7 intervals down the reef slope to a depth of 30 m. Surveys were conducted to:1. measure the interaction reach of a range of coral species. "Reach" is defined as the distance from the retracted tissue of the dominant coral to the nearest living tissue of the subordinate coral2. determine if there are differences in the frequency of aggressive interactions with depthThe interaction mechanism causing tissue death was not investigated.