News / Industry News & Events / Coral Microbiomes Offer Clues for Resilience and Conservation (01/16/19)

Coral Microbiomes Offer Clues for Resilience and Conservation

01/16/19

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Some coral species might be better equipped to adapt to a warmer, more acidic ocean. Finding out which ones, and why, could be the key to saving reefs around the world.

The prognosis for coral reefs has continued to spiral downward over the past year. A report published by the Intergovernmental Panel on Climate Change in October found that coral reefs could decline by between 70% and 90% if the global average temperature increases by 1.5C above preindustrial levels. At 2C, the chances of any reefs surviving become slim to none.

Some scientists, not willing to throw up their hands and call it quits on saving coral, are seeking out a more strategic plan of action by trying to identify species that can tolerate warmer, more acidic water and figure out why they survive. Driving conservation efforts toward these more tolerant species might secure the crucial ecosystem functions that reefs provide, like housing fish and protecting coastlines.

Andra Grottoli, a biologist at Ohio State University, tested a hypothesis that a corals microbiomeall the bacteria that live in the slimy mucus of the reefis somehow connected to its resilience. In a study published earlier this year, she found that microbiome stability and physiological health seem to go hand in hand.

We dont know if its the stable microbiome that facilitates a healthy host physiology, or if its the host physiology that facilitates a healthy microbiome. But they go together, Grottoli said while presenting her work in December at AGUs Fall Meeting 2018 in Washington, D. C. Grottoli was also recently awarded the Ocean Sciences Voyager Award by AGU for her contributions to ocean science and leadership in the field.

Identifying a Winner

Grottolis microbiome research builds on three previous papers she coauthored that looked at coral health under the dual stressors of warmer water and water with a lot more carbon dioxide in it. She said that when she first proposed the experiment, there were almost no other studies examining these two stress factors at the same time.

Back in 2011, she and her colleagues tested how four species responded to a ramp-up in temperature and acidity over 24 days, approximating expected ocean conditions at the end of this century. Taking a holistic approach, they assessed coral health using more than 10 criteria, examining both the host organism and the symbiotic algae that live in the coral.

The result of this earlier work was the discovery of a resilience champion. Turbinaria reniformis, commonly known as yellow scroll coral, tolerated the changing conditions well. In a photo comparing coral fragments from the treatment and control groups, its impossible to tell the difference. Acropora millepora, on the other hand, turned out to be much more sensitive. This branching coral became shrunken and pale and lost algae. The question then was, What was it about the yellow scroll coral that allowed it to adapt?

We asked ourselves whether the coral microbial community may be playing a role, Grottoli said. The corals microbiomes may be important to immune response, similar to the way the bacterial community in the human gut helps us stave off disease.

Grottoli didnt have funding for another study, so she did a pilot investigation with just two species. She took fragments of coral from the 2011 experiment back out of the freezer and partnered with a colleague at Ohio State, a microbiologist named Michael Wilkins, to analyze the composition of their microbial communities.

She found that in the most sensitive species of the initial group, the diversity of the microbial communities decreased by 40% after the 24-day ramp-up. The microbes that remained turned out to be related to bacteria known to cause coral diseases.

By contrast, the yellow scroll coral, the most tolerant species, once again seemed to have everything going for it, with no significant change in its microbial community.

We concluded that coral like Turbinaria would be good targets for conservation and restoration because they seem to be pretty robust on multiple fronts, Grottoli said.

Grottoli didnt have funding for another study, so she did a pilot investigation with just two species. She took fragments of coral from the 2011 experiment back out of the freezer and partnered with a colleague at Ohio State, a microbiologist named Michael Wilkins, to analyze the composition of their microbial communities.

She found that in the most sensitive species of the initial group, the diversity of the microbial communities decreased by 40% after the 24-day ramp-up. The microbes that remained turned out to be related to bacteria known to cause coral diseases.

By contrast, the yellow scroll coral, the most tolerant species, once again seemed to have everything going for it, with no significant change in its microbial community.

We concluded that coral like Turbinaria would be good targets for conservation and restoration because they seem to be pretty robust on multiple fronts, Grottoli said.

Emily Pontecorvo (eponte@mit.edu; @emilypont), Graduate Program in Science Writing, Massachusetts Institute of Technology, Cambridge

Citation: Pontecorvo, E. (2019), Coral microbiomes offer clues for resilience and conservation, Eos, 100, https://doi.org/10.1029/2019EO113949. Published on 15 January 2019.