Hong Kong University Study Finds Reward and Punishment System in Coral-Algae Relationship

Hong Kong University Study Finds Reward and Punishment System in Coral-Algae Relationship
Using stable isotope techniques, Dr Shelby McIlroy was able to unravel the flow of nutrients between different species of algae in their host, a Caribbean coral species. Courtesy of M.A. Coffroth
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The University of Hong Kong released a study that found corals may ‘punish’ the algae that live inside them by cutting off their food supply if such algae become selfish and renege on their part of the resource-sharing deal with the coral as part of their symbiosis—a mutually beneficial relationship.

The study published on Nov. 7, 2022, in the academic journal Microbiome is the findings of Dr. Shelby McIlroy of the Swire Institute of Marine Science (SWIMS) and the School of Biological Sciences at The University of Hong Kong (HKU) and her collaborators.

McIlroy and her research team found that the stable isotopes combined with genetic techniques allowed them to track the currency exchange between the partners, that is, different species of algae in their host. In this case, the currency is nutrients in the form of carbon and nitrogen.

The results showed that the coral might punish the cheaters and reward the honest partners. McIlroy said in a press release on Jan. 12, 2023, that their study showed that corals seem to limit the supply of nutrients to the symbiotic algae that are less beneficial to them as a way of fostering more beneficial algae symbionts.

Sea temperatures are rising, and the seas are becoming too hot for the algae inside the coral. When water temperatures spike, algae die, and so does the coral itself—a phenomenon known as bleaching. Episodes of bleaching are now becoming increasingly common, and most of the world’s coral reefs are now threatened by it. McIlroy said if she could get the coral to host the species of algae that can handle higher temperatures—a form of ‘coral probiotics,’ it could prevent bleaching and buy more time for corals threatened by the warming of the oceans.

However, she also added that she needed to understand the biology of corals and how they might react to these interventions so that they could work effectively and efficiently.