Predictions of Turbidity Due to Enhanced Sediment Resuspension Resulting from Sea-Level Rise on a Fringing Coral Reef: Evidence from Molokai, Hawaii

Accelerating sea level rise associated with global climate change will affect sedimentary processes on coral reefs and other shoreline environments by increasing energy and sediment resuspension On reefs sedimentation is known to increase coral stress and bleaching as particles that settle on coral surfaces interfere with photosynthesis and feeding and turbidity induced by suspended sediment reduces incident light levels Using relationships developed from observations of wave orbital velocity water surface elevation and suspended sediment concentration on a fringing reef flat of Molokai Hawaii predictions of the average daily maximum in suspended sediment concentration increase from similar to 11 mg/l to similar to 20 mg/l with 20 cm sea level rise The duration of time concentrations exceeds 10 mg/l increases from 9% to 37% An evaluation of the reduction of wave energy flux through breaking and frictional dissipation across the reef flat shows an increase of similar to 80% relative to the present will potentially reach the shoreline as sea level increases by 20 cm Where the shoreline exists on low, flat terrain the increased energy could cause significant erosion of the shoreline Considering the sediment budget the sediment flux is predicted to increase and removal of fine grained sediment may be expedited on some fringing reefs, and sediment in storage on the inner reef could ultimately be reduced However increased shoreline erosion may add sediment and offset removal from the reef flat The shifts in sediment availability and transport that will occur as result of a modest increase in sea level have wide application to fringing coral reefs elsewhere as well as other shoreline environments