Coral life history differences determine the refugium potential of a remote Caribbean reef

Remote populations can influence connectivity and may serve as refugia from climate change. Here, we investigated two reef-building corals (Pseudodiploria strigosa and Orbicella franksi) from the Flower Garden Banks (FGB) - the most isolated, high-latitude Caribbean reef system that retains high coral cover. We characterized coral size frequency distributions, quantified larval mortality rates and onset of competence, estimated larval production, and created detailed biophysical models incorporating these parameters to evaluate source-sink dynamics from 2009 to 2012. Mortality rates were similar across species but competency differed dramatically: P. strigosa was capable of metamorphosis within 2.5 days post fertilization (dpf), while O. franksi were not competent until >20dpf and remained competent up to 120dpf Despite these differences, models demonstrated that larvae of both types were similarly successful in reseeding the FGB. Nevertheless, corals with shorter pelagic larval durations (PLD), such as P. strigosa, were highly isolated from the rest of the Caribbean, while long PLD corals, such as O. franksi, could export larvae to distant northern Caribbean reefs. These results suggest that FGB coral populations are self-sustaining and highlight the potential of long PLD corals, such as endangered Orbicella, to act as larval sources for other degraded Caribbean reefs.