Prevalence and progression of macroscopic lesions in Orbicella annularis and O. faveolata on shallow fringing reefs of St. Kitts

Abstract

The endangered corals Orbicella annularis and O. faveolata are crucial to Caribbean reefs because of their large size and contribution to reef framework. The objective of this study was to describe the prevalence and progression of macroscopically evident lesions affecting Orbicella spp. in shallow fringing reefs in St. Kitts. Cross-sectional surveys in the spring of 2017 demonstrated 8 predominant lesion patterns affecting 59% of corals (95% CI: 55.8-62.1%), including annular yellow-brown pigmentation, focal brown pigmentation, focal bleaching, diffuse bleaching, annular black surface deposit, focal tissue loss with skeletal erosion, focal grey pigmentation, and growth anomaly. Longitudinal surveys of 47 tagged corals were performed from August 2016-May 2017 to track lesion progression. The 2 most common lesions, annular yellow-brown pigmentation (n = 30), and focal brown pigmentation (n = 21), showed mean (±SD) partial colony mortality growth of 0.26 ± 0.5 and 0.21 ± 0.45 cm2 d-1, respectively. Annular pigmentation progression severity was associated with a marginating band of bleaching (ordinal odds ratio [OOR] = 11.0), and yellow rather than brown color (OOR = 3.8). Bleaching lesions (n = 13), occurring during a time of elevated sea surface temperature, were most severe during October-December 2016, and persisted through April 2017, months after heat stress had subsided. Annular black surface deposits (n = 3) were associated with rapid progression of acute tissue loss, whereas focal tissue loss with skeletal erosion (n = 2) regressed within months, and focal grey pigmentation (n = 2) was quiescent for the length of the study. This study enforces concern for the extent to which Orbicella spp. are declining due to disease.