Reef Morphology and Community Structure along a Fluvial Gradient, Rio Bueno, Jamaica.

This study assessed the combined effects of natural riverine inputs and variation in wave energy upon the reef development and coral community structure in the small embayment of Rio Bueno, northern Jamaica. The embayment is subject to seasonally variable fluvial discharges of terrigenous sedi- ment and freshwater. Water quality deteriorated with increasing proximity to the embayment head and river mouth, with sediment influx resulting in high turbidity levels and a reduced light environment within inner and central embayment areas. Sedimentation rates within the central embayment peaked at 43.2 mg cm �2 d �1 during this study. Coral communities were only present in the outer, clear water sites and central, moderately turbid sites, but were absent from the inner embayment areas which are adjacent to the river mouth. Mean (± 1 SD) hard coral cover was 11.6% (± 8.1), with a maximum of 42.9% along the reef flat in the medium- impacted zone. Within this zone, framework development was spatially and bathymetrically restricted. However, when compared with clear water sites, greater species richness, higher coral cover and a greater abundance of large, dome-shaped corals occurred. Common species included Diploria strigosa, Porites as- treoides and Siderastrea siderea, which are suggested to be those most tolerant to sediment stress. At sites with coral framework (central and outer sites), algal cover was positively correlated with increasing distance from the head of the embayment, whilst coral cover was negatively correlated with increasing distance from the head, peaking in the central embayment.