Influence of marine reserves on coral disease prevalence.

Predicted increases in disease with climate warming highlight the need for effective management strategies to mitigate disease effects in coral communities. We examined the role of marine protected areas (MPAs) in reducing disease in corals and the hypothesis that the composition of fish communities can influence coral health, by comparing disease prevalence between MPA and non-protected (control) reefs in Palau. Overall, the prevalence of diseases pooled, as well as the prevalence of skeletal eroding band (SEB), brown band disease (BrB) and growth anomalies (GAs) individually in major disease hosts (families Acroporidae and Poritidae), were not significantly reduced within MPAs. In fact, the prevalence of SEB was 2-fold higher within MPAs overall; however, the 4 studied MPAs were ineffective in enhancing coral assemblage or fish stock health. A negative association between the prevalence of SEB and richness of a fish species targeted by fishers in Palau highlights the potential role that well-managed MPAs could play in reducing SEB. The composition of coral communities and their susceptibility to bleaching also influenced the prevalence of disease on the studied reefs. The prevalence of diseases pooled and SEB were positively associated with the cover of major disease hosts (families Acroporidae and Poritidae), and the prevalence of BrB and bleaching were also positively associated. Although our study did not show positive effects of MPAs on coral heath, we did identify the potential for increased fish diversity within MPAs to reduce coral disease. Our study also highlights the complexity of relationships between fish assemblages, coral community composition and coral health on Indo-Pacific reefs.

Coral diseases on Philippine reefs: genus Porites is a dominant host.

While it is generally assumed that Indo-Pacific reefs are not widely affected by diseases, limited data suggest a number of diseases and syndromes that appear to differ from those currently under study in the Caribbean. This report presents the results of a baseline survey of coral diseases in 2 regions in the Philippines: the Central Visayas and the Lingayen Gulf. Mean prevalence for all diseases observed was 8.3 +/- 1.2% (mean +/- SE; n = 8 reefs), with Central Visayas reefs showing higher disease prevalence (11.6 +/- 2.8%; n = 4 reefs) than those of Lingayen Gulf (5.1 +/- 1.4%; n = 4 reefs). Five diseases and syndromes were described; 3 of these-Porites ulcerative white spot disease (PUWS) (prevalence = 8.96 +/- 2.2%), tumors (prevalence = 1.0 +/- 0.5%) and pigmentation response (prevalence = 0.5 +/- 0.2%)--occurred frequently in both regions and targeted the genus Porites. Correlation between disease prevalence and number of Porites colonies was fairly strong (r2 = 43.4), though not significant, and no correlation was seen between prevalence and either the amount or diversity of hard coral. Porites is a major reef-builder in the Indo-Pacific comprising 30% of hard coral colonies on our surveyed reefs, and is generally thought to be a hardy, long-lived genus. Diseases targeting this robust group present an as yet unquantified risk to Philippine reefs and could result in major changes in reef structure.