Impacts of recreational scuba diving at sites with different reef topographies

Increased participation in marine recreation and tourism has been accompanied by concern for the impacts that these activities have on coral reef environments. We investigated how the topography of coral reef dive sites influences the type and amount of damage done by SCUBA divers to living corals. Independent observations were made on 150 qualified SCUBA divers at six dive sites within the Great Barrier Reef World Heritage Area, Australia. Two sites each had reef topographies that were characterised by steep slopes ('Pinnacles'), gently sloping (40 degrees-60 degrees, 'Shoulders'), or near-horizontal substrata ('Gardens'). The number of contacts each diver made with the substratum and the number of times corals were broken were recorded and compared across all six sites and among the three topographic categories. The rate at which divers broke corals varied markedly among dive sites, but was not clearly related to reef topography. Divers broke more corals per 10 min interval (1.8 +/- 0.77, mean +/- I SE) at one of the Shoulder sites than at any of the other five locations (0 to 0.28 +/- 0.24). Benthic assemblages at this site contained the largest percentage cover of branching corals of all of the sites used in the study (24% +/- 4%, cf. 0%-10% at the other five sites). All of the breakages that we observed were sustained by corals that had a branching morphology. Our results suggest that the topography of coral reef dive sites is not a useful predictor of the amount of damage done by SCUBA divers. More important is the morphological composition of benthic assemblages at the site. Knowledge of biological influences on the sensitivity of different sites to impacts of SCUBA divers will allow managers to match high-risk activities, such as diver training, with suitably durable locations. (C) 1997 Elsevier Science Ltd.