Abstract

Improper implementation of sedimentation controls at a seawall construction site at Vega Baja beach, Puerto Rico, resulted in significant high turbidity followed by localized mass mortality of threatened Elkhorn coral (Acropora palmata) populations along a east-west gradient during August 13 - 20, 2010. A total of 63 tagged coral colonies along eight permanent transects (0.5 to 2.2 km downstream of the construction site) were unblemished before the event. Those located below 0.9 km away showed an increase in % frequency infections (22 - 78% with decreasing distance). None of the corals located farther away were impacted. Fifty more corals were tagged after the incident along two transects at 0.6 (east) and 0.8 km away (middle). A total of 90% of the corals were partially killed by patchy necrosis (PN) at each site, with 75% still showing active infections at the east and 50% at the middle site. Also, 45% of the colonies showed 26 - 50% recent tissue loss at the east, while 23% of those from the middle showed only 6 - 25% tissue loss. Live % coral cover was significantly lower at the east site (44%) than at the middle (66%). Recent mortality was higher at the east site (37%) in comparison to the middle (20%). Frequency of large lesions was significant at the east site. This event was more devastat-ing than a previous one during the winter of 2008. Sea surface temperature anomaly was +2.0°C during this event, suggesting that the combined stress of high turbidity and warm temperature could have triggered such an impact.

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