Coral reefs around the world are threatened by warming temperatures which cause them to bleach 鈥� but they might get some relief through probiotics.
In healthy reefs, corals get up to 80 per cent of their energy from the photosynthetic algae that live within their tissue alongside other microorganisms like bacteria. Heat stress disturbs these relationships and can ultimately lead to coral death.
at the Federal University of Rio de Janeiro in Brazil and at King Abdullah University of Science and Technology in Saudi Arabia and their colleagues have found that introducing a cocktail of bacteria found in healthy reefs can help corals hit by heat stress, by making them more resilient.
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鈥淲e know that it鈥檚 biologically possible to develop a medicine for corals that can actually prevent mortality,鈥� says Peixoto. 鈥淭he idea is that we would try to find common bacteria that we always find in the reef 鈥� so native bacteria that live in the reef 鈥� that could [help] several different [coral] species.鈥�
The team selected beneficial bacteria taken from a healthy heat-resistant coral and gave it as a probiotic to coral heated to 30掳C in a simulated heat stress event in an aquarium in the lab.
Corals that hadn鈥檛 been given the probiotic died after being exposed to heat stress 鈥� but the probiotic enhanced corals recovered and survived.
This may be because bacteria have far shorter generation times than corals, and so can evolve on much faster timescales to adapt to the higher temperatures. Not only that, but the bacteria seem to evolve features that enhance the survival prospects of their coral hosts. This would explain why, after changing the bacteria present within the coral microbiome, the team saw a knock-on effect on the expression of particular coral genes that enhances coral survival rates. 鈥淲e saw a real genetic reprogramming of the coral host triggered by the beneficial bacteria,鈥� says Peixoto.
The researchers experimented with giving the probiotics to corals both before and during a heat stress event.
鈥淲e could protect better when we use the prevention approach,鈥� says Santoro. 鈥淲hen you know that the temperature is going to increase, we can go to the field and give probiotics to the coral and then these corals are going to be stronger to pass through the stress.鈥�
In the lab tests, the probiotic was suspended in solution and applied to the coral鈥檚 surface. The researchers say they are now working with engineers on a way to apply it to corals across larger reef areas in the oceans.
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