- IVF-grown corals survive heatwave better than older corals
- Young corals retain heat-resistant algae; older ones bleach
- IVF boosts coral genetic variety, aiding climate resilience
Young corals grown using in vitro fertilization (IVF) and placed in reefs across the United States, Mexico, and the Caribbean have stunned scientists, with the majority surviving last year’s record marine heatwave as older corals suffer.
A study discovered that 90% of the young IVF-created corals assessed stayed healthy and colorful, retaining the algae within them and providing nutrients. In contrast, just around 25% of older non-IVF corals remained healthy.
The others, including vast colonies that may have survived for decades, were either bleached by the heat, expelling the algae from their tissues and turned white, or paled, expelling some of the algae. Some people perished in the heatwave before the survey was performed.
Dr. Margaret Miller, principal author, and research director at Secore International, a reef conservation organization, stated, [The heatwave] was a terrible moment. However, I was intrigued and shocked that the data revealed such an extreme pattern.
During the last five years, Secore devised a type of IVF to breed young corals. Divers collected coral spawn, which was then utilized to fertilize eggs in the laboratory. The resulting young corals were then deposited on reefs throughout the Caribbean to establish colonies.
Most coral restoration attempts have historically relied on fragmentation techniques, which include breaking corals into smaller pieces and transplanting them to a new area. Breeding corals with IVF enhanced genetic variety, giving them a better chance of adjusting to heat over time than fragmentation, which produces exact clones. “Natural selection back in the reef environment will choose the best ones,” Miller told me.
The 771 baby corals in the study are a fraction of the thousands bred each year by Secore and partner institutions. They dwell in restored reefs off Mexico, the Dominican Republic, the US Virgin Islands, and the Dutch Caribbean territory of Bonaire and Curaçao.
Researchers at Sombrero Reef in the Dominican Republic studied juvenile and old elkhorn corals (Acropora palmata). The reef was formerly teeming with giant branching species, but most died during an outbreak of white band disease in the 1980s. The reef presently contains a few older corals unaffected by the disease, and many young elkhorn corals have been cultivated to repair the reef.
When Maria Villalpando, a researcher at the Dominican Foundation for Marine Studies (Fundemar), assessed the corals following peak heat stress last October, she discovered that the young elkhorn corals were healthy. “They weren’t even pale,” she explained. The older elkhorn corals, however, fared poorly. “Sadly, we lost most of them after this bleaching event.”
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It needs to be clarified why young corals are more heat resistant. There are numerous ideas, but Miller believes they can obtain symbiotic algae that can withstand heat more efficiently. They will experiment with other forms of algae, some of which can withstand higher temperatures. “They are quite exploratory in those early stages,” Miller told me. She said the juvenile corals eventually settle on symbionts that work for them.
Previous studies indicate that if juvenile corals live long enough, they will likely become less tolerant to heat stress as they age, leaving them more vulnerable as global temperatures increase.
Miller stated that bleaching events have occurred every other year for the previous six years in Australia, whereas in the Caribbean, they occur around every five years. She said that even if a colony survives a bleaching episode, its reproduction capacity is hampered for several years afterward.
“So now that the intervals between these heat waves have become so short, coral propagation alone is unlikely to change the fate of these populations,” Miller told reporters. We must address the underlying causes of global climate change. However, we must boost coral populations as this may give us some time.
