How microbe restoration is needed to help save corals

On International Microorganism Day we dive deeper into the key role of microbes and their contribution to coral health and coral restoration success. Raquel Peixoto and Christian Voolstra, KAUST (King Abdullah University of Science and Technology) , explore how microbe restoration is needed to help save corals.

Science to the rescue

Climate change is transforming once-pristine ecosystems into constantly changing environments, resulting in significant disruptions and the loss of biodiversity. While changes can be easily seen at a macroscale level if we swim through a reef paled by bleached corals, equally drastic changes are taking place at a microscale – invisible to the naked eye – as microbial life and microbiomes are being disrupted inside corals.

In their recent paper, Raquel Peixoto and Christian Voolstra, highlight the need to invest in microbiomes restoration and rehabilitation if one aims for faster and more successful coral restoration attempts. To restore corals to a healthy, almost pristine state, we also have to restore their microbes. But the baseline has already shifted.

Corals are endangered and so are microbes

Microbes shape our planet, all life within it and even the relationships between different organisms. However, tiny as they may be, microbes, especially the good ones, are also greatly threatened and affected by global changes. With warmer temperatures, weather extremes and other environmental changes, we have been witnessing the emergence and spread of pathogens in ecosystems like coral reefs.

Over the last few decades, corals have drastically declined as a result of a changing habitat. Pronounced future losses are further expected in response to forthcoming global and anthropogenic actions. Such changes affect the microbial communities that live within corals and are crucial for their functioning and health.

The shifting baseline

What is a pristine state? The way nature was during the generation before ours, or the generation before that? Which conditions should we target to restore coral reefs?

The “shifting baseline trap” is the perception that the (altered) state experienced by the previous generation is/was the pristine state, even though in reality it represents an already altered condition.

As environmental conditions change and disturb corals, the relationships they keep with their microbes may cease to exist. But it gets even worse. What was once a beneficial relationship with microbes may turn into an opportunistic one, with microbial communities shifting from beneficial to pathogenic, which significantly affects corals’ health and could even lead to death. A flourishing and stable coral reef ecosystem depends on healthy corals, which are intrinsically linked to healthy microbial communities. Disrupted microbiomes are at the core of significant biodiversity loss, and it is expected that these disruptions will only continue.

Friends, not foes

Reducing CO2 emissions is key to secure a safe future for corals, but additional measures are also needed to cope with the ongoing impacts. Whereas we can’t go back to pristine, undisturbed states – and we don’t know what this would look like – we can retain beneficial microbes, block the growth of pathogens and improve coral reef environment by making corals healthier through microbiome restoration and rehabilitation. This can be done through the use of probiotics, microbiome transplants and other microbial therapies. It all comes down to this: unhealthy corals will receive a dose of beneficial microbes, helping them cope with their stressful environments. It won’t totally solve the problem of mass coral die-offs or dramatic biodiversity losses, but it will most likely buy corals some time until other restoration approaches are put into place.

The researchers have no doubts: marine conservation should consider microbiomes restoration and rehabilitation as inevitable part of the solution. Some concerns will arise on how humans will be manipulating coral microbiomes and interfering with nature. However, it is important to highlight that coral microbiomes have already changed; the aim is to return them to a state where the microbial communities they host are beneficial instead of detrimental to their health.

Read the full article here >>

Peixoto RS and Voolstra CR (2023) The baseline is already shifted: marine microbiome restoration and rehabilitation as essential tools to mitigate ecosystem decline: www.frontiersin.org/articles/10.3389/fmars.2023.1218531/full

And the framework for safe microbiome stewardship:

Peixoto, R.S., Voolstra, C.R., Sweet, M. et al. Harnessing the microbiome to prevent global biodiversity loss. Nat Microbiol 7, 1726–1735 (2022). https://doi.org/10.1038/s41564-022-01173-1