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Optimized in vitro fertilization techniques to boost Caribbean coral restoration efforts

A study published in PeerJ unveils refined techniques for in vitro fertilization (IVF) in four key Caribbean coral species, offering a crucial advancement in coral reef restoration efforts.

Researchers from SECORE International, the CARMABI Foundation, and the University of Amsterdam have developed new insights into the optimal conditions for coral breeding, which could significantly enhance larval production and bolster declining coral populations.

The study examined four broadcast-spawning coral species: Diploria labyrinthiformis, Colpophyllia natans, Pseudodiploria strigosa, and Orbicella faveolata. These species are essential for maintaining the Caribbean's marine ecosystems, yet their populations have been severely impacted by climate change, diseases, and other anthropogenic factors.

Key findings:

• Gamete viability: Coral gametes remain viable for at least four hours after collection, allowing researchers to mix gametes from multiple sites to enhance genetic diversity.
• Fertilization timing: Brain corals (D. labyrinthiformis, C. natans, and P. strigosa) fertilize quickly—within just 15 minutes of sperm-egg co-incubation—reducing handling risks.
• O. faveolata requirements: This foundational reef-building coral requires longer co-incubation times (60–120 minutes) for optimal fertilization success.
• Sperm concentration: Minimum sperm concentration thresholds were identified at 10⁵–10⁶ cells/mL, providing critical benchmarks for IVF protocols.

These findings offer actionable guidelines for coral IVF practitioners, enabling higher larval yields while minimizing gamete wastage and embryo damage. Such advancements could help restore isolated coral populations and counteract natural sperm limitations in the wild.

Implications for coral restoration

Coral reefs are among the most biodiverse and threatened ecosystems on the planet, and breeding corals for restoration is emerging as a key tool in their recovery. By optimizing fertilization techniques, restoration practitioners can scale up efforts to repopulate degraded reefs with healthy, genetically diverse corals.

"Our study highlights the importance of tailoring IVF protocols to specific coral species," said Dr. Valérie F. Chamberland, lead author and researcher at SECORE International.

"By fine-tuning these methods, we can increase the efficiency and impact of coral restoration projects, giving these vital ecosystems a better chance of recovery."

The study also underscores the potential of IVF to overcome reproductive barriers in coral populations that are geographically isolated or genetically disconnected, expanding the possibilities for large-scale restoration initiatives.

The findings of this study will be directly applied to improve coral breeding protocols and distributed within SECORE's network of restoration practitioners. With climate change continuing to threaten coral reefs worldwide, advancements like these are crucial for preserving marine biodiversity and the livelihoods that depend on healthy oceans.