The West Hawai'i Coral Recruitment Project; Recruitment Dynamics of Scleractinian Corals along the Kona Coast of the Big Island of Hawai'i

Martin, R.A.; Walsh, W.J.

Results of long-term coral recruitment monitoring off West Hawaii Island. Maintenance of adequate levels of coral recruitment is vital to sustain coral reefs. Because early life stages are often more susceptible than adults to environmental stressors, data on settlement and recruitment can help predict potential effects of disturbance from, and resilience to, environmental change. The spatial-temporal variability of scleractinian coral recruitment is currently being investigated along the west coast of Hawai'i. From April 2004 to present, terra cotta tiles have been placed at nine sites spanning the leeward side of Hawai'i Island. Eight tiles at each of the nine sites have been replaced biannually before and after known seasonal peaks in coral reproduction and recruitment. The tiles are then processed for microscope analysis, and coral recruits are counted and identified to genus. Several spatial and temporal trends are starting to emerge in this ongoing study. The relative contribution of the different families of recruits (Poritidea: 46.9%, Acroporidea 33.9%, Pocilloporidea 12.6%) and recruitment rates (average of all sites: 25 recruits m-2 year-1) recorded along the Kona Coast are comparably low to other areas around the state of Hawai'i. The two northern most sites, Waiakaʹilio and Puako, have had significantly higher densities of juvenile corals, with much lower densities at all the sites to the south. Approximately 77% of the time the coral recruits preferred to settle out on the bottom outside edge of the tiles compared to the vertical edges (9.78%) and the top (1.20%). This is likely the result of intense competition with filamentous algae, and/or grazing by herbivorous fish and urchins which can occur on the exposed top surface of the tiles. Peak settlement of coral larvae occur 87% of the time during the summer months (approximately April - September) in species with and without planktonic larvae. These distinctive characteristics in recruitment patterns underline the important role of life history strategies in understanding the spatial-temporal patterns of coral populations. The comparably low coral recruitment rates noted in this study indicate that recovery from natural and/or anthropogenic influences will be slow.

The West Hawai'i Coral Recruitment Project; Recruitment Dynamics of Scleractinian Corals along the Kona Coast of the Big Island of Hawai'i

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