Depth-related Barriers to Genetic Connectivity Among Northwestern Atlantic Lophelia pertusa Populations

The cold-water coral Lophelia pertusa is a cosmopolitan species and a major constituent of deep-water coral banks in the Northwestern Atlantic Ocean. Extrapolation from recent multibeam mapping data and visual observations revealed a greater extent of deep coral habitat off the southeastern U.S. coast than previously known. Knowledge regarding the degree of connectivity between L. pertusa populations off the southeastern U.S. coast and the Gulf of Mexico is imperative to effective management and mitigation efforts given that the degree of connectivity will influence the stability of populations over time (resilience) as well as their probability of recovery from potential anthropogenic impacts. Recent L. pertusa collections expanded the geographic coverage (waters off Florida through the mid-Atlantic) and depth range (215- 800m), allowing for a more thorough investigation into the forces that structure populations. Thirteen highly variable microsatellite markers were used to genotype over 400 samples of L. pertusa representing fourteen deep reefs and canyon locations. Like previous analyses, discontinuity was detected between the Gulf of Mexico and Northwestern Atlantic populations offshore of the southeastern coast. However, weak yet significant genetic structuring was detected among L. pertusa locations off the southeastern coast, suggesting limited connectivity. An isolation-by-depth pattern of gene flow was supported, with genetic distinction apparent among populations shallower and deeper than 500 m, which may be explained by different water masses these populations experience. To expand the geographic scope of connectivity analyses and improve predictions and decision making leading to wise resource management across the North Atlantic Ocean, restriction site associated DNA sequencing (RADseq) will be coordinated through the NOAA Atlantic Seafloor Partnership for Integrated Research and Exploration (ASPIRE) and European Union’s Horizon 2020 (ATLAS) campaigns.