Proceedings of the 11 th International Coral Reef Symposium, Ft. Lauderdale, Florida, 7-11 July 2008 Session number 18 The prevalence of skeletal growth anomaly and other afflictions in scleractinian corals at Wai‘ōpae, Hawai‘i M. Takabayashi 1 , T.M. Gregg 1 , E. Farah 1 , J. Burns 1 , K. Teves 1 , N.H. Cody 1 1) University of Hawai‘i at Hilo, 200 W. Kawili St. Hilo Hawai‘i 96720 USA Abstract. The health states of scleractinian corals were assessed at Wai‘ōpae, southeast Hawai‘i Island, where approximately half of the tide pools belong to a Marine Life Conservation District (MLCD) while the other half lies outside the MLCD boundary. The susceptibility of corals to afflictions is species-dependant with Porites compressa being the most (22.5±3.9% unhealthy) and Pavona varians the least (1.1±0.27% unhealthy) susceptible. The proportion of unhealthy corals was: higher inside the MLCD than outside for Montipora and Pocillopora; not different between the two areas for Porites; and higher outside MLCD than inside for Pavona. Skeletal growth anomaly (SGA) was disproportionably observed in Montipora spp., especially M. capitata, 13.6 (±0.37) % of which were afflicted by this condition. There is no clear correlation between the progression of SGA (change in size or frequency) and species, location, or season. Some coral colonies are showing a level of resilience against SGA while others have succumbed to it within the Wai‘ōpae population. The prevalence of coral afflictions at Wai‘ōpae is unusually high compared to other sites in the Hawaiian Archipelago, but the causes are unknown. Monitoring of coral health at this site is continuing with an incorporation of assessment of correlations to water quality characteristics. Key words: coral disease, skeletal growth anomaly, Wai‘ōpae, Hawai‘i, Montipora Introduction Prevalence and severity of coral diseases are reported to be increasing worldwide (reviewed in Harvell et al. 2007). Types of diseases or reduced health states seem to vary according to coral species and location. In many cases, the effort to positively identify the pathogen responsible for the onset of coral diseases has been met with challenges. It is generally believed that water quality exacerbates the susceptibility of corals to pathogenically or non- pathogenically compromised health. For example, moderate increases in nutrient concentrations have been shown to substantially increase the severity of coral diseases (Bruno et al. 2003). However, specific causal relationships between particular water quality characteristics and individual coral disease are poorly understood. With the mechanisms of disease progress and mortality of corals being poorly understood, it is quite plausible that disease could even enable coral survival through reproduction of disease resistant genotypes in some cases (Lesser et al. 2007). Until the effects of coral diseases are better understood it is difficult to assess the fate and threat posed to corals in waters subjected to harmful anthropogenic influences. Coral reefs surrounding high gradient island systems, such as Hawai‘i, are particularly vulnerable to influences from terrigenous sources. This is especially true on the island of Hawai‘i because the substrate is predominately composed of porous basaltic rock and, being young on a geological timescale, lacks an abundance of soil for bioremediation. Further compounding these effects is the human population growth. Hawai‘i Island has experienced one of the fastest human population growths over the last decade or so (23.6% increase in 1990-2000) in the State of Hawai‘i (U.S. Census Bureau 2000). Synergistically, these factors have a great potential to produce direct anthropogenic effects on fringing coral reef ecosystems. Some of these effects can be manifested in states of reduced health of corals. Several symptoms for poor health in reef-building corals have been reported in Hawai‘i and range from bleaching, coral tissue loss, infectious diseases for which pathogens have been identified, and other abnormalities in cellular, tissue, and skeletal morphologies of unknown causes (Gulko et al. 2000, Friedlander et al. 2005, Sutherland et al. 2004). Coral diseases have been found on most major coral species of the main Hawaiian islands (Porities lobata, P. compressa, Montipora capitata, M. patula, and Pocillopora meandrina: Gulko et al. 2000, Friedlander et al. 2005). The last few decades has seen an increase in the frequency of coral diseases over a range of depths and habitats in Hawai‘i (Gulko et al. 2000, Friedlander et. al 2005). Different coral genera exhibit different types and prevalence of diseases at different locations in Hawai‘i (Aeby 2004, this study). These conditions, with the exception of 820