Restoration potential of corals from urbanized and marginal habitats in Florida (Phase 2)

Given decades of population declines on Florida’s Coral Reef and recent large-scale disturbance events such as the stony coral tissue loss disease (SCTLD) epidemic and the fourth global coral bleaching event, it is critical to identify priority coral habitats and populations for targeted conservation and restoration. ‘Urban corals’ have been discovered on artificial substrates in urbanized habitats such as the Port of Miami, and research by the Coral Program at the University of Miami’s Cooperative Institute for Marine and Atmospheric Studies (CIMAS) and NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) since 2018 has shown these corals are more resilient to environmental stressors than their reef counterparts. This project evaluated the spawning activity of urban corals through field-based observations using KiloCam timelapse camera platforms and fecundity assessments via histological analysis, across two urbanized sites: the Port of Miami and Port of Palm Beach. Long-term KiloCam timelapse deployments resulted in 301,743 images in summer 2025 and 253,916 images in spring 2026, confirming spawning activity in all four studied species. Observed spawning did not occur during the anticipated timing windows of reef corals, but rather as a prolonged dribble of gamete bundles both within and outside of those windows, likely driven by artificial light at night (ALAN). Fecundity analysis confirmed that viable gametes were produced in sampled corals at the Port of Miami—with all five species (Colpophylia natans, Diploria labyrinthiformis, Orbicella faveolata, Pseudodiplora clivosa, and P. strigosa) producing oocytes comparable in size to Caribbean reef corals, and post-spawning samples showing empty mesenteries confirming gamete release. At the Port of Palm Beach, reproductive viability was more variable: approximately half of sampled colonies were non-reproductive, and post-spawning cores from P. strigosa showed signs of oocyte reabsorption. Urban corals remain a conservation priority, but given asynchronous spawning that reduces the likelihood of natural crossbreeding with reef populations, they are best suited for land-based assisted sexual reproduction to increase genetic diversity. Taken together, these outcomes add to growing knowledge on the ecological benefits of urban coral populations in the persistence and recovery of Florida’s Coral Reef.