US Virgin Islands Pillar Coral Spawning Workshop

Pillar coral is a stony coral species that was once abundantly found throughout Florida and the Caribbean Sea. This coral species has a unique growth pattern, growing upwards in stacks that look like “pillars”.  

However, pillar coral is one of the most decimated species of stony coral in the region for many reasons including its high susceptibility to Stony Coral Tissue Loss Disease (SCTLD) and is now listed as threatened under the Endangered Species Act. In Florida and much of the Caribbean, there are so few colonies of this species left that it is considered functionally extinct.    

Healthy pillar coral creates habitat for marine life. Credit: NOAA Fisheries 

Like many other stony coral species, pillar corals are predicted to spawn after the August full moon, a chance for fertilization of new genetically-distinct larvae that will settle onto available reef substrate to become eventual pillar coral colonies.  

Different coral species have varying methods of spawning; elkhorn and staghorn, which CRF has consistently monitored in recent years, are hermaphroditic, meaning that each colony releases a bundle that has both eggs and sperm inside. However, pillar corals are gonochoric, meaning that each colony is either “male” (releases sperm) or “female” (releases eggs).  

With so few pillar coral colonies left in the wild, this trait makes it even more difficult for sperm or eggs to find each other from other colonies for successful fertilization. Researchers and restoration practitioners are hoping to increase the chances of successful spawning and assist fertilization by holding fragments of remaining pillar corals in offshore and on-land nurseries to connect the remaining populations again.  

However, fertilization is a very delicate process, and researchers are continuing to learn more about pillar coral spawning characteristics.  

Genetically unique pillar coral fragments from the USVI held in aquariums at Coral World Ocean and Research Initiative (CWORI), where they are hoped to spawn. Credit: Blake Gardner.  

In late August, Bailey Thomasson, USVI Reef Restoration Coordinator for CRF, attended a pillar coral learning exchange workshop in St. Thomas that brought together researchers and practitioners from the U.S. Virgin Islands and Puerto Rico. 

Throughout the week, the group monitored pillar coral spawning activity at the University of the Virgin Islands (UVI) and Coral World Ocean and Reef Initiative (CWORI) in hopes of collecting gametes and assisting in fertilization. After late-night hours of watching these corals for any signs of spawning each night, it was easy to convince yourself that spawning was about to happen after any twitch or sway of the coral’s tentacles!  

Participants at the pillar coral learning exchange workshop ranged from researchers to practitioners to resource managers, representing Coral Restoration Foundation, Coral World Ocean and Reef Initiative, University of the Virgin Islands, NOAA, The Nature Conservancy, Sociedad Ambiente Marino, Institute for Socio-Ecological Research, Sea Ventures Marine Response Unit, National Marine Sanctuary Foundation, and Thriving Islands LLC. Credit: Blake Gardner.  

After four nights of observation, only two corals spawned at CWORI by releasing a few eggs. Since no males spawned at the same time, no fertilization could occur. There are many reasons why spawning may not have happened during the predicted window this year – many of these corals survived but are likely still recovering from the 2023 bleaching event and there is also the possibility that rapidly changing ocean conditions due to climate change are altering these corals’ spawning window.  

These observations and learning exchanges are critical for understanding more about what coral spawning may look like in the future amidst increasing stressors. Successful spawning and fertilization efforts will allow new coral larvae to enter into the toolbox for the continued protection and restoration of these fragile coral species.   

Workshop participants observing pillar corals during the spawning learning exchange workshop, using red lights that don’t disturb the light cycle for spawning. Credit: Bailey Thomasson 

The USVI pillar coral learning exchange workshop was funded by NOAA’s Coral Reef Conservation Program (CRCP), coordinated with the National Marine Sanctuary Foundation (NMSF), and hosted by the University of the Virgin Islands (UVI) and Coral World Ocean and Reef Initiative (CWORI) labs.  

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