Growth Rate of Stony Corals of Broward County, Florida: Effects from Past Beach Renourishment Projects

The skeletal growth of hermatypic (reef-building) corals is a sensitive indicator of environmental conditions and perturbations. In particular, excessive sedimentation and turbidity act to depress coral growth because energy expenditure is required to remove sediment and because turbidity reduces light energy necessary for coral health and nutrition.

Normalized annual growth (linear skeletal extension) rates of Broward County, Florida reef-building corals were over 16 years (1985-1970). Star corals ( Montastrea annularis ) and brain corals ( Diploria labyrinthiformis ) were collected from each of four reef sites at two depths (9m and 18m). Collection areas were located in the vicinity of possible adverse sedimentation/turbidity effects from one or more of six past beach renourishment projects.

Coral growth differences among sites at particular years and among years within sites were statistically evaluated. Years tested included those of and subsequent to each of six past beach renourishment projects. The results are suggestive that, in general, Broward County beach renourishment projects have had minor or no influence on currently living off-shore corals.

However, following the Hollywood-Hallandale renourishment project of 1979, D. labyrinthiformis from the Hollywood 18m site exhibited significantly lower normalized growth compared to other sites. This may not represent effects from the renourishment project. At the Hollywood site M. annularis from both 9m and 18m and D. labyrinthiformis from 9m did not exhibit significantly lowered growth in comparison to other sites.

Site averages of absolute coral growth indicated that southern 9m specimens had higher rates of growth than northern counterparts for M. annularis . In the southern collection sites, 9m growth of both species tended to be greater than 18m growth.

Correlation analysis indicated that the time pattern of coral growth is similar among sites, species, and depths. Comparison of time series of coral growth data to recorded environmental variables (temperature and salinity) revealed a positive relation with salinity (water density) variations.