JUL 01, 2016

The Coral Microbiome - a Sentinel of Coral Health

WRITTEN BY: Carmen Leitch
Coral reefs are known to be crucial for the health of the marine species that rely on them but also to the planet as a whole. Recent events have stressed coral around the world, however. They are facing serious threats from pollution, overfishing and bleaching brought on by climate change. Those factors impact not only the coral itself but also the microbial communities that interact with them. As we become more aware of their importance, research studies of coral have gained more interest.
The Global Coral Microbiome project is a research project that aims to elucidate the role of microbial organisms that reside in and around coral reefs. The scientists collaborating on this project aim to describe microbial diversity in every major group of reef-building corals in a multitude of distinct ecosystems from around the planet. They hope to find the genomic sequences and metabolic powers of crucial coral bacteria, and to determine whether the makeup of coral microbial communities aids in understand how different coral species respond to stress or disease.

"The next step is to look through that kind of microbial soup and find which bacteria may be the beneficial ones, understand how they're responding under temperature changes, and what contributions they're making to the coral," Tracy Ainsworth, a molecular biologist at James Cook University in Australia, told The Christian Science Monitor.
"We really want to know what are all the pieces of the puzzle that fit together to give corals the best chance" at survival, Ainsworth continued. "And understanding the microbiome, and particularly the beneficial microbiome, is one piece of that puzzle we need to better understand." The microbiota of coral could be "like a guard, an early warning, and a level of protection that we may take for granted," Ainsworth explains.
In this video from a meeting the International Coral Reef Symposium, Joe Pollock from Penn State discusses a variety of research areas. His talk centers on several topics; the structure of microbiota or microbial communities across various coral organisms or polyps, the relationship of bacteria and coral and how they fit together in an evolutionary tree, as well as how geography can influence all of these things.

Coral has various layers or compartments, so researchers sampled each individually. They did find changes in the community structure and richness or diversity between the layers. Interestingly, there are also differences in the way the different components of coral respond to environmental factors. Coral age, seasonality had an effect on diversity, and the depth of the effect changed depending on coral compartment.

While it’s unclear what effect evolution had on coral microbiota, the function of coral, or the life history of the coral, did create a divergence in microbial composition. There has also been tremendous evolutionary diversification in coral around the world, so they made sure to reflect that wide array of coral in their studies.
Surprisingly, some scientists are finding that coral is more resilient to the negative influences that are pressuring it in the modern world, as shown in the video above. A recent global study involving 34 conservation groups and universities shows that some coral is remaining healthy in the face of stress. Investigators were trying to locate areas like Kiribati that had coral that managed to hold on to fish populations. They found that if local fishermen could access freezers, overfishing caused problems for the reef. However, when locals were principally using the reef for their own food source, the reef was sustaining life.

One thing seems to be certain; coral reefs and their associated microbial communities need to be monitored and considered as environmental factors continue to cause stress on them.

Sources: Science, The Christian Science Monitor, Oregon State University, Science Daily