Scuba diving

The first use of modern mask, fins and snorkel can be traced back to the Mediterranean in the 1920s and 1930s. 1942 saw the development of the first fully automated aqualung and regulator. Since then diving has grown from being a little known and dangerous sport to one of the world's most popular adventure activities. In 1999 PADI, provided certification for over 800 000 divers! Worldwide there are now over 15 million recreational divers.

Picture courtesy of Topham.

Divers may damage coral through direct physical contact with their body or fins, but may also cause harm to colonies by stirring up sediment. Coral reefs at Eilat, northern Red Sea, are among the most heavily used in the world for recreational diving, with >250,000 dives per year on only 12 km of coastline. Field observations of diver behaviour revealed ca 10 incidents of reef contact per dive, mostly via raising of sediments onto the reef, but also involving direct breakage of corals. A study looking at diver impact in Sharm el Sheikh, Egypt, found there were more damaged coral colonies, loose fragments of coral and partially dead or abraded corals in intensely dived areas than control sites. Though the differences between heavily and lightly dived areas may be relatively unimportant biologically they were quite considerable from an aesthetic point of view. Another study in the Caribbean island of Grand Cayman, found that (1) hard and massive coral cover decreased with an increase in number of divers, and (2) when moving away from the dive mooring buoy. High intensity sites also typically exhibited more dead coral and coral rubble. Montastrea annularis seems to be particularly sensitive to diver impact. The health of this massive coral species is important, as these colonies constitute the main reef building corals at the studied sites. Researchers on the Great Barrier Reef found that 32 out of 214 divers caused damage to corals, mostly by kicking the reef with their fins. The study also revealed that divers carrying underwater cameras (non-naïve photographers) and males caused more damage than divers without cameras or females! Despite these results, there seems to be considerable uncertainty surrounding concerns about biological impacts of SCUBA diving on coral reef communities - overall most divers and snorkelers seem to cause little damage. Long term studies will be needed to ascertain such impacts. In the short term however there is a clear concern about the reduced amenity values associated with increased use by divers of certain coral reef areas. Thus the question arises, what is acceptable in terms of damage and what isn't, i.e. what is the carrying capacity - critical threshold level of use - of a particular site. The problem with this approach is that individual divers vary greatly in their behaviour and thus in the amount of damage they can cause to a reef. As a consequence, imposing strict limits on the number of divers allowed to dive a site might unnecessarily deny many the opportunity to experience unique dive sites. However, it does facilitate management of dive sites (mostly marine protected areas) and helps reduce the potential impact of divers on coral communities and marine fauna.

Anchoring of diving boats can also cause serious damage to coral communities. However, in most diving locations morring buoys have been deployed and strict regulations exist prohibiting anchoring directly on coral spurs.