Larval dispersal patterns and connectivity of Acropora on Florida’s Coral Reef and its implications for restoration

Abstract

Since the 1980s, populations of Acropora cervicornis and A. palmata have experienced severe declines due to disease and anthropogenic stressors; resulting in their listing as threatened, and their need for restoration. In this study, larval survival and competency data were collected and used to calibrate a very high-resolution hydrodynamic model (up to 100m) to determine the dispersal patterns of Acropora species along the Florida’s Coral Reef. The resulting connectivity matrices was incorporated into a metapopulation model to compare strategies for restoring Acropora populations. This study found that Florida’s Coral Reef was historically a well-connected system, and that spatially selective restoration may be able to stimulate natural recovery. Acropora larvae are predominantly transported northward along the Florida’s Coral Reef, however southward transport also occurs, driven by tides and baroclinic eddies. Local retention and self-recruitment processes were strong for a broadcast spawner with a long pelagic larval duration. Model simulations demonstrate that it is beneficial to spread restoration effort across more reefs, rather than focusing on a few reefs. Differences in population patchiness between the Acropora cervicornis and A. palmata drive the need for different approaches to their management plans. This model can be used as a tool to address the species-specific management to restore genotypically diverse Acropora populations on the Florida’s Coral Reef, and its methods could be expanded to other vulnerable populations.

Biophysical models resolution affects coral connectivity estimates

“…In this study, we have shown that, all other things being equal, the spatial resolution of a biophysical model influences the resulting dispersal patterns and connectivity metrics. We therefore suggest that the scale at which a model can provide recommendations for reef management, for example regarding the delineation of Marine Protected Areas 47 , 48 or the identification of the most suitable reefs for restoration measures 49 , 50 , can not be finer than its spatial resolution. Any recommendation based on model results is therefore valid and applicable at scales coarser than that resolution.…”

Hurricanes enhance coral connectivity but also superspread coral diseases

“…When competent larvae are over a reef, we assume they can settle at a rate 20% per hour based on larval vertical swimming speed, as in King et al. (2023).…”

“…20% per hour based on larval vertical swimming speed, as inKing et al (2023).Finally, once all the necessary parameters were set, virtual particles were released on all FCR reefs. The reef shapefile used to locate the different reefs in FCR was extracted from the "coral reefs and hardbottom" layer of the Unified Florida Reef Tract Map (Florida Fish and Wildlife Conservation Commission-Fish and Wildlife Research Institute, 2017).…”

Coral restoration for coastal resilience: Integrating ecology, hydrodynamics, and engineering at multiple scales

“…These are both facilitated by regional circulation patterns and the spatial orientation of a reef (Holstein et al, 2014; Leichter et al, 2013). Recruitment is a primary driver of coral reef recovery from disturbance (Holbrook et al, 2018), and connectivity is an important input into selection of restoration sites and species composition of coral outplants (Figure 3; King et al, 2023). Some potential restoration sites may be more likely to consistently attract and retain larvae (or sustain local coral species that have short pelagic durations) than other sites, increasing the probability of self‐sustaining coral populations.…”