Real-Time Coral Stress Observations Before, During, and After Beach Nourishment Dredging Offshore SE Florida

Beach nourishment in Southeast Florida involves dredging sand source borrow areas located between offshore reefs. From May 2005 to February 2006 Broward County, FL. nourished 10.9 km of beach with 1.5 ×106 m3 of sand. As part of a program to monitor potential reef community impacts, a visual stress index was developed from laboratory experiments and histological analyses for three stony coral species (Montastrea cavernosa, Solenastrea bournoni, and Siderastrea siderea). Scoring involved healthy = 0; moderately stressed = 1 (polyp swelling, increased mucus); markedly stressed = 2 (coloration changes, increased mucus secretion, tissue thinning); and severely stressed = 3 (severe swelling/thinning tissue erosion/necrosis). Colonies were scored weekly at sites adjacent to borrow areas and control sites pre-, during, and post-dredging. Permit conditions were established which would suspend dredging based on mean stress index values above 1.5 at 50% of monitored sites adjacent to borrow areas. This condition was never met. However, three hurricanes, passing the region during dredging, contributed to an elevated mean stress level above 1.0. Post-dredging observations documented recovery to pre-dredging stress levels. This program was effectively used to monitor stress on a sensitive marine habitat adjacent to sediment dredging activities.