Different marine species and their larvae have characteristics that can expand or contract their potential dispersal, which can add complexity to the management of species assemblages. Here we used a multi-scale biophysical modeling framework, the Connectivity Modeling System, for the analysis of network connectivity for 5 Caribbean coral reef-associated species in order to gauge similarities and dissimilarities among species as well as among Caribbean regions. We estimated local dispersal and retention to assess regional exchanges, and our results revealed that the population structures of coral and fish are different and should thus have dissimilar management requirements in many regions, with some notable exceptions. Populations of Porites astreoides corals appear fragmented, suggesting that loss of adult colonies in any region may significantly impact regional recruitment success and connectivity. At the other end of the spectrum, populations of bluehead wrasse Thalassoma bifasciatum are highly connected, and removal of adults in any single region would not imply future recruitment failure in that region. We suggest using a 'diversity of exogenous settlement' index as a proxy of recolonization potential, which is related to the stability of regional connectivity networks. We demonstrate that resolving multispecies larval transport dynamics helps identify regions of both network stability for multi-generational connectivity (e.g. stable larval sources and corridors) pertinent to regionallevel management and network inconsistencies among species which are pertinent to the success of local management.

Whether mesophotic reefs will behave as refugia for corals threatened by global climate change and coastal development depends on vertical exchange of larvae between diverse habitats. Here we use a biophysical model of larval dispersal to estimate vertical connectivity of a broadcasting (Orbicella faveolata) and a brooding (Porites astreoides) species of coral in the US Virgin Islands. Modeling predicts subsidy to shallow areas by mesophotic larvae of both species based on local hydrology, adult reproductive characteristics, larval traits, and a wide range of scenarios developed to test depth-sensitive factors, such as fertilization rates and post-settlement survivorship. In extreme model scenarios of reduced fertilization and post-settlement survivorship of mesophotic larvae, 1-10 % local mesophotic subsidy to shallow recruitment is predicted for both species, which are demographically significant. Although direct vertical connectivity is higher for the broadcaster, the brooder demonstrates higher local multigenerational vertical connectivity, which suggests that local P. astreoides populations are more resilient than those of O. faveolata, and corroborates field studies. As shallow habitat degrades, mesophotic-shallow subsidy is predicted to increase for both species. This study is the first of its kind to simulate larval dispersal and settlement between habitats of different depths, and these findings have local, regional, and global implications for predicting and managing coral reef persistence in a changing climate.

The persistence of natural metapopulations may depend on subpopulations that exist at the edges of species ranges, removed from anthropogenic stress. Mesophotic coral ecosystems (30–150 m) are buffered from disturbance by depth and distance, and are potentially massive reservoirs of coral diversity and fecundity; yet we know little about the reproductive capabilities of their constituent species and the potential for these marginal environments to influence patterns of coral reef persistence. We investigated the reproductive performance of the threatened depth-generalist coral Orbicella faveolata over the extent of its vertical range to assess mesophotic contributions to regional larval pools. Over equal habitat area, mesophotic coral populations were found to produce over an order of magnitude more eggs than nearby shallow populations. Positive changes with depth in both population abundance and polyp fecundity contributed to this discrepancy. Relative larval pool contributions of deeper living corals will likely increase as shallow habitats further degrade due to climate change and local habitat degradation. This is a compelling example of the potential for marginal habitat to be critical to metapopulation persistence as reproductive refugia.