Assisted breeding, also called Coral IVF, involves the collection of gametes from healthy corals, fertilization under controlled conditions, and the subsequent reintroduction of larvae to degraded reefs. This approach seeks to augment natural recruitment processes and introduce genetically diverse and potentially stress-tolerant individuals into coral populations.

Coral Recruitment Enhancement 

Boström-Einarsson et al. (2020) reported that larvae reared through coral IVF and settled onto degraded reef areas exhibited higher survival rates compared to naturally settled larvae. This suggests that controlled breeding and rearing conditions can produce robust larvae capable of enhancing coral cover in restoration sites. Recent projects by the Australian Institute of Marine Science (AIMS) estimated a 100-fold increase in fertilization rates over natural breeding, which might provide significant increases in coral recruitment and settlement. 

Restoration of Genetic Diversity

Maintaining genetic diversity is crucial for the adaptive potential of coral populations. Assisted breeding facilitates the mixing of gametes from different colonies, thereby increasing genetic variability among offspring. Baums et al. (2019) found that coral populations restored through assisted gene flow exhibited greater genetic diversity and enhanced resilience to environmental stressors, underscoring the importance of genetic considerations in restoration efforts.

Strategy

Long-term survivorship, effects on trophic and ecosystem dynamics, and future resilience are important considerations for implementing assisted breeding. As this approach is relatively new, we are looking forward to emerging data on settlement, recruitment, and survivorship. Environmental safety can be determined by proximity and comparable traits of donor and recipient reefs, and is expected to be safe if the donor and recipient reefs are the same. This approach requires waiting for annual spawning events, and significant field operations during and after spawning to guide fertilization. It may also be possible to add removable substrates for settled larvae that can later be transplanted onto degraded reefs. 

References

• Boström-Einarsson, L., et al. (2020). Coral restoration—A systematic review of current methods, successes, failures and future directions. PLOS ONE, 15(1), e0226631. https://doi.org/10.1371/journal.pone.0226631

• Baums, I. B., et al. (2019). Considerations for maximizing the adaptive potential of restored coral populations in the western Atlantic. Ecological Applications, 29(8), e01978. https://doi.org/10.1002/eap.1978

• van Oppen, M. J. H., et al. (2015). Building coral reef resilience through assisted evolution. Proceedings of the National Academy of Sciences, 112(8), 2307–2313. https://doi.org/10.1073/pnas.1422301112

• Peixoto, R. S., et al. (2017). Beneficial microorganisms for corals (BMC): Proposed mechanisms for coral health and resilience. Frontiers in Microbiology, 8, 341. https://doi.org/10.3389/fmicb.2017.00341