Survival, growth, and branch production of unattached fragments of the threatened hermatypic coral Acropora cervicornis

Fragmentation has been regarded as the most important reproductive strategy in the threatened reef building coral Acropora cervicornis. Before the Caribbean-wide collapse experienced by A. cervicornis, asexual reproduction may have served as an effective source of new colonies to sustain and/or enhance local population growth. However, baseline information on the demographic success of fragments in nature is limited, hampering our ability to estimate the real contribution of asexual fragmentation to current population growth. In this study, natural occurring fragments of A. cervicornis were monitored for 18 months at two sites in Puerto Rico in order to quantify their survival, growth, and branching dynamics. Fragment survivorship did not exceed 26%, growth rates were relatively low with mean values ranging between 0.0242 ± 0.0168 (SE) and 0.0906 ± 0.0301 (SE) cm d− 1, and fragments barely produced new branches. No significant differences were found when comparing these demographic traits for different size categories. The relative low rates of survival, growth and branch production of natural fragments suggest that asexual fragmentation may not currently be a significant source of recruits for populations of this threatened coral.