Probiotics kept Red Sea corals from bleaching during a heat wave
Scientists at King Abdullah University of Science and Technology treated corals on a Red Sea reef with beneficial bacteria during a 2022 heat wave. Treated corals kept their colour and their algae kept working, while untreated corals declined. It is the first evidence that probiotics can help corals in the wild through a heat wave.
When corals overheat, the partnership between the coral and the algae living in its tissue breaks down. The coral turns white, or bleaches, and can die. Scientists at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia have been testing whether beneficial bacteria can help.
In 2021 microbial ecologist Raquel Peixoto set up an underwater lab on a reef about 15 kilometres off the Saudi coast, which her team calls the Coral Probiotic Village. When a heat wave hit the Red Sea in 2022, the team prepared two probiotic mixes of bacteria taken from healthy local corals, plus heat-killed versions of each, known as postbiotics.
Water temperatures ranged from 30.9 to 32 degrees Celsius. Over 15 days, lead author Erika Santoro and colleagues dived eight times to release the treatments next to Acropora corals, recording colour and how well the corals' algae were photosynthesising. Although the heat wave had already begun, corals given the probiotics and one of the postbiotics kept their colour and photosynthetic efficiency, while untreated corals declined. The results were published in the journal Cell Reports.
"Demonstrating that the treatments actually mitigate heat stress in situ, in a real reef situation, is fantastic," said Andrea Grottoli of Ohio State University, who was not involved.
The researchers are clear about the limits. Only one coral species was treated, a longer study is needed to show effects on growth and survival, and treating whole reefs is labour intensive. Postbiotics may prove cheaper and easier to store.
Probiotics will not stop climate change, but they could buy reefs time, and this is the first sign they work on a real reef.
Source: Probiotics prevented coral bleaching during a Red Sea heat wave: Study (Mongabay).
Written by the HappyGood desk from the primary source linked above and checked against it. Every story links its source. Corrections: [email protected].
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