Corals may “punish” the symbiotic algae that live within their tissues by blocking their food supply if the algae become selfish and renege on their part of the resource-sharing deal.
Corals can host several species of symbiotic algae at the same time, but it seems not all are honest. Some take advantage by retaining more nutrients for their own needs, instead of passing them to the coral. In this way, the “selfish” algae gain an advantage over more beneficial species that grow slower because they share their nutrients more generously. This cheating ultimately undermines the long-term health and growth of the coral itself.
The research is the work 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. Using stable isotope techniques, McIlroy was able to unravel the flow of nutrients between different species of algae in their host, a Caribbean coral species. “Stable isotopes combined with genetic techniques allow us to track the currency exchange between the partners. In this case, the currency is nutrients, in the form of carbon and nitrogen,” McIlory explained.
The results showed that the coral might indeed punish the cheats and reward the honest partners. “Our 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 algal symbionts,” McIlroy added.
More than ever, understanding how corals control and manipulate their symbiotic algae is crucially important for coral survival. If scientists 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.
Main image: Digital-Reefs.com