“Closing the Coral Circle”: Approaches to overcome the recruitment bottleneck preventing coral recovery in the Caribbean

Coral reefs around the world are threatened by multiple stressors, including changing temperatures, overfishing, pollution, and disease. The survival and resilience of corals will depend on their ability to adjust to these environmental challenges through adaptive evolutionary processes. Since the 1970s, the reef-building corals of the Florida Reef Tract (the world’s third largest barrier reef) have declined due to a complex mix of local and global pressures: a pattern reflected throughout the Caribbean. Elkhorn coral, the region’s dominant reef-builders, once had a Florida population in excess of 500,000 colonies. Even before the 2023 bleaching event, only 200 elkhorn genets remained.

 

Despite the historical loss of reef-building corals, active restoration efforts have shown that corals can survive and reach sexual maturity in Florida and the Caribbean. However, the health of Caribbean reefs and their long-term resiliency will depend on restored populations to sexually reproduce and adaptively evolve to changing environmental conditions. Unfortunately, no wild-born juvenile corals have been observed along the Florida reef tract in the past 15 years and there is evidence that normal development of very young corals is being disrupted throughout the Caribbean, preventing the completion of the coral life cycle. A return to growth via sexual reproduction on Florida and Caribbean reefs will be essential for increasing genetic diversity and the regeneration of the tract at the necessary pace, scale, and resiliency to meet our goals.

 

The “Closing the Coral Circle” workshop united international experts in coral biology and ecology, advanced forensics, engineered biology, and robotics to tackle this critical conservation challenge. Together, we discussed various aspects of coral biology, as well as biological, chemical, and physical factors in the corals’ environment that could be hindering the completion of the coral life cycle. Major themes identified fell into two categories: (1) problems for recruitment that are well-understood, and (2) knowledge gaps in our understanding of coral recruitment dynamics and how these might contribute to the problems. In this presentation, we will discuss the outcomes of the workshop including our “service blueprint” for coral recruitment, which is a visual map of the challenges, knowledge gaps, and potential solutions, (available on Zenodo) to aid the community in project planning.