Hawai'i Coral Reef Network

DIVER Impacts on 
coral reefS at Kealakekua BaY, Hawai’i


Both control and impact sites had similar substratum composition and hence met the assumption of the method that they were similar prior to the study. Therefore, assuming that natural processes which cause bleached and broken coral occurred at similar frequencies at both sites, any differences in these parameters is likely to be associated with the major difference between these sites: the frequency of human use by swimmers, snorkelers and divers. Kealakekua Bay, being one of the most popular dive tour destinations in Kona, receives at least 50-200 visitors a day (personal observations). Additional visitors may hike or drive down the trail to the Cook Monument or swim, sail or kayak over from Napoopoo across the bay. In contrast, swimmers are rarely seen at the control site. 

The results of this study found no significant differences between impact and control sites in changes in coral cover, or the incidence of bleached and broken coral. Therefore, there is no statistical support for the premise that divers at Kealakekua Bay are causing damage to the reef. However, in all cases the decline in coral cover and the incidence of bleached and broken coral was higher at the impact relative to the control site. Thus, these data suggest that divers may be having an impact to the reef but over a one year period these changes are too small to distinguish from natural changes in coral abundance, bleaching and breakage. Thus, the principle results of this study strongly support the conclusion that a longer study be initiated to further investigate this possibility. Given the importance of reefs in Hawai'i and the increasing pressures being applied by swimmers, snorkelers and divers, further study is warranted.


Clark, A. M. and D. Gulko. 1999. Hawai’i’s State of the Reefs Report, 1998. Department of Land and Natural Resources, Honolulu, HI. 41pp.

Grigg, R. W. 1997. Hawaii’s coral reefs: status and health in 1997, the International Year of the Reef. In: Status of Coral reefs in the Pacific. R. W. Grigg and C. Birkeland, eds. University of Hawaii Sea Grant College Program. Honolulu, HI. Pp. 59-72.

Richmond, R. H. 1993. Coral reefs: present problems and future concerns resulting from anthropogenic disturbance. Amer. Zool. 33: 524-536.


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Last update: 1/25/2005