Abstract Summary
Monitoring of individual ephemeral coral species such as Acropora cervicornis is difficult because of frequent fragment or displacement, yielding individual colonies nearly impossible to track long-term. However, much of the remaining A. cervicornis exist as low density populations comprised of individual colonies, and we must understand individual colony dynamics of the species in order to develop proper monitoring guidelines and success metrics for population enhancement programs. In this study, the spatial and temporal components of A. cervicornis colony residency and retention were explored by 1) measuring changes in colony abundance, 2) evaluating two methods for colony fate tracking, 3) estimating colony residence and retention rates, and 4) determining if colony size effects colony residency. All parameters were measured within 3.5 m radial plots (n=56) established between numerous sites (n=11) in three sub-regions of the Florida Reef Tract from June 2011 to July 2015. Colony residence times were similar between methods used for fate tracking and less than 16% of colonies remaining after two years. A majority of colony loss came from complete colony dislodgement and not mortality. Mean colony abundance by sub- region did not change significantly between survey events; however, median colony residency time was less than one year, and three month retention rates were between 29-88% for all sub- regions, indicating significant and frequent colony movement within sites. The probability of a colony remaining through the end of the study was over three times greater in the Dry Tortugas (0.12) sub-region than Broward (0.03) and Middle Keys (0.04). Colony size had a positive effect on retention time although the relationship was weak (between 9 and 19%). Our data show that fate tracking is likely underestimating population growth, propagation, survival, and health of the species, ultimately suggesting the need to modify how A. cervicornis are being monitored to describe long-term success and species recovery. Furthermore, these results indicate the success of a population enhancement program should not be defined exclusively by fate tracking outplanted colonies, but should utilize a systematic site level monitoring approach to capture individual species dynamics.
