Hope For Coral Reefs After IVF Colonies Survive Record Heat Event

Young corals bred using in vitro fertilisation (IVF) and planted in reefs around the US, Mexico and the Caribbean have surprised scientists, after most survived last year's record marine heatwave, while older corals struggled. From a report: A study has found that 90% of the young IVF-created corals surveyed remained healthy and colourful, holding on to the algae that live within them and supply them with nutrition. In contrast, only about a quarter of older non-IVF corals remained healthy. The rest, including large colonies that may have lived for centuries, were either bleached by the heat -- expelling the algae from their tissues and turning white -- or paled, expelling some of the algae. Some died in the heatwave before the survey was conducted.

Dr Margaret Miller, lead author and research director at Secore International, a reef conservation organisation, said: '[The heatwave] was a horrible time. But I was impressed and surprised that the data came out with such an extreme pattern.' The young corals were bred over the past five years using a version of IVF developed by Secore. Divers collected coral spawn, which was used to fertilise eggs in the laboratory. The resultant baby corals were then planted on reefs across the Caribbean to form colonies.

Most coral restoration efforts have historically focused on fragmentation techniques -- where corals are broken into smaller pieces and transplanted to a new location. Rather than producing exact clones, as fragmentation does, breeding corals by IVF increased the genetic diversity, giving them a higher chance of adapting to heat over time. 'Natural selection back in the reef environment will choose the best ones,' said Miller. The 771 young corals in the study -- a fraction of the thousands bred each year by Secore and partner institutions -- live in restored reefs off Mexico, the Dominican Republic, the US Virgin Islands, and the Dutch Caribbean territories of Bonaire and Curacao.

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