Partial mortality in Porites corals: Variation among Philippine reefs

Partial mortality or tissue necrosis was quantified in the massive scleract inian coral Porites at three sites in The Philippines (Bolinao, NW Luzon: P uerto Galera, Mindoro: and El Nido, N Palawan). Over all. 15 +/- 1 (mean +/ - standard error, 642 replicates) percent of colony area was dead, mean col ony area was 11.35 +/- 127 cm(2), and lesion density was: 1.7 +/- 0.1 dm(-2 ) Total live coral cover varied between 20 and 63 % in belt transects, and Porites and Acropora cover were inversely correlated. ANOVA models incorporating effects of site. colony size, sedimentation rate s, wave exposure and depth were highly significant but explained only a sma ll proportion of the variation observed in lesion density and percent dead area (respectively 8 and 2 %). Lesion density was found to vary significant ly with site (contributed 29 % to this explained variance), decrease with i ncreasing colony area (33 %). and increase with increasing sedimentation (2 3 %) and wave exposure (14 %). Colony size was significantly explained by t he factor site (contributing 61 % to the total 29 Sc explained variance) an d depth (34 %). with the smallest colonies being observed in Bolinao and th e largest in El Nido. Densities of lesions were highest in Bolinao, interme diate in Puerto Galera, and lowest in El Nido. This pattern is parallel to intensity of human reef exploitation and opposite to that in colony size, l ive coral cover and Acropora cover. Since only a small part of the observed variance in partial mortality estimators was explained by the ANOVAs, othe r factors not quantified hers must have been more important (e.g. disease i ncidence, predation. human exploitation).