Stony coral health is negatively related to terrestrial and silt-clay sediment flux in the nearshore US Virgin Islands
Leslie Marie Henderson
Sedimentation can have deleterious impacts on coral reef ecosystems and human activities are increasing rates of terrestrial silt and clay deposition to nearshore environments. However, in most cases there is no information on natural and modified rates of sediment deposition from which to evaluate changes in sedimentation rates or their impacts on marine ecosystems. We sampled sedimentation rates across a range of coral reef environments in the US Virgin Islands using standard sediment traps. We found high variability in rates of sediment deposition that corresponded temporally to rain and swell events, as well as spatially by distance from shore and the degree of watershed development. We also evaluated coral health and found that sites with higher rates of sediment deposition showed more bleaching, partial mortality (an integrated measure of past disturbance) and all forms of coral health impairment combined. Less evidence was found for a relationship with coral diseases, though this may have been affected by an inability to detect transient disease signs at the temporal resolution of coral health surveys. Our results suggest that nearshore coral reef ecosystems associated with altered watersheds in the US Virgin Islands are experiencing elevated levels of stress from terrestrial sediments, and that this stress is likely to impair long-term survival.
USVI Department of Planning and Natural Resources
Leslie Marie Henderson
Sedimentation can have deleterious impacts on coral reef ecosystems and human activities are increasing rates of terrestrial silt and clay deposition to nearshore environments. However, in most cases there is no information on natural and modified rates of sediment deposition from which to evaluate changes in sedimentation rates or their impacts on marine ecosystems. We sampled sedimentation rates across a range of coral reef environments in the US Virgin Islands using standard sediment traps. We found high variability in rates of sediment deposition that corresponded temporally to rain and swell events, as well as spatially by distance from shore and the degree of watershed development. We also evaluated coral health and found that sites with higher rates of sediment deposition showed more bleaching, partial mortality (an integrated measure of past disturbance) and all forms of coral health impairment combined. Less evidence was found for a relationship with coral diseases, though this may have been affected by an inability to detect transient disease signs at the temporal resolution of coral health surveys. Our results suggest that nearshore coral reef ecosystems associated with altered watersheds in the US Virgin Islands are experiencing elevated levels of stress from terrestrial sediments, and that this stress is likely to impair long-term survival.
USVI Department of Planning and Natural Resources