SAND KEY BEACH RENOURISHMENT PROJECT: FUNCTIONALITY OF MITIGATIVE ARTIFICIAL REEFS AND IMPLICATIONS FOR FUTURE PROJECTS

To meet state permit requirements for mitigation of impacts associated with beach renourishment activities on Sand Key, Pinellas County constructed a total of 16 artificial reefs between 1997 and 2006. Biological monitoring was conducted on three of these reefs to determine at what age mitigative artificial reefs within the study area become biologically equivalent with the surrounding natural hardbottom. The three installations were compared to two natural hardbottom sites. Each of the five sampling units consisted of six temporary transects, 10 meters in length, established at the time of data collection. A point-intercept method of assessment was conducted every 0.5 meters. Sand and other sediment types had the highest percent cover at all sites, both natural and artificial, followed by turf algae. Excluding turf, the dominant functional groups across all sites were macroalgae, sponge, tunicate, octocoral and hydroid. Dominant species included the octocoral Leptogorgia virgulata, at both natural and artificial reef sites, and the sponge species Cliona celata at natural hardbottom sites. Mutivariate analyses using PRIMER®v6 indicated that the benthic habitat on nearshore artificial reefs within the study area become biologically similar to the surrounding natural hardbottom between two and five years after installation, and by 10 years post-installation the artificial reefs reach a benthic community complexity which supersedes that of the natural hardbottom. This study provides a timeframe for functional equivalency implications for permit conditions and management of future nearshore artificial reef projects in the area