Risk assessment of SCUBA diver contacts on subtropical benthic taxa

Subtropical reefs are biogeographic transition zones, providing critical habitat for a range of tropical, subtropical and temperate biota, including many endemic species. To date, limited research has been conducted on assessing the level of SCUBA diving risks to subtropical benthic habitats. This study surveyed 407 SCUBA divers to determine the types and rates of contact presenting the greatest risk to benthic taxa. Data were aggregated to give the total number of severe contacts for each diver. Site-level analysis based on 95% confidence level showed that severe impacts were more probable as reef complexity increased vertically. A general linear regression model was used to assess the level of risk to habitat based on the contact type and benthic percentage cover. SCUBA tank, camera, diver's knee and untethered equipment created the greatest proportion of severe impacts to benthic taxa. As benthic percentage cover increased for Scleractinia, Echinodermata, Ascidiacea, Porifera, susceptibility and vulnerability to severe impacts also increased. Abrasions, breaks, compression and mucus release were common forms of impact. Risk assessment findings suggest that subtropical benthic taxa are highly susceptible to SCUBA diver impacts. Targeted risk reduction is required in future management strategies.