The human gut houses masses of microbes. Some microbes can make people fall ill, while others work to balance gut health. But humans aren’t the only species that rely on these microorganisms to maintain good health. Coral reef ecosystems depend on microorganisms to recycle organic nutrients and matter. Additionally, these cells help provide nutrients to corals and other life living on reefs. Researchers from Woods Hole Oceanographic Institution examined the microbes in coral reef water by scrutinizing eight reefs in the U.S. Virgin Islands over a timeframe of seven years, experiencing periods of hurricane and coral disease disturbance along the way. 

“Coral reefs have been declining for decades. Climate change, hurricanes, disease, and other stressors have played a major part in that.” said Cynthia Becker, first author of the study and recent graduate of the MIT-WHOI Joint Program.

“Reefs provide habitat for about 25% of all marine species, but they also support billions in tourism and fishing. It is important for us to monitor changes in coral reefs as they are happening and the microbes in their environment can really help us do that.”

The research, “Microorganisms uniquely capture and predict stony coral tissue loss disease and hurricane disturbance impacts on the U.S. Virgin Islands reefs,” published in Environmental Microbiology describes the influence coral reef disturbances have on microbes. 

During the two major occurrences studied, hurricanes Irma and Maria in 2017 and the stony coral tissue loss disease outbreak beginning in 2020, there were escalations of ammonium concentration in the water, resulting in a 34% decline in Prochlorococcus bacteria. 

Prochlorococcus is a miniscule photosynthetic bacteria that supports the health of corals and other life reliant on them, but also produces oxygen for our atmosphere by bringing new carbon into the coral’s ecosystem. 

“A lot of how we study coral reefs is done on a macroorganismal level. However, alterations in corals and fish communities might remain unseen for months or years. This makes it difficult to track the health of these vulnerable reefs in real time,” explained Amy Apprill, a microbial ecologist at WHOI and corresponding author of the research. 

“Microbes are the hidden engines of coral reefs, and they grow quickly and are responsive to nutrient, temperature, pH and other conditions. By sampling the water, we can see the immediate impacts of disturbances and intervene to support the reefs before the situation potentially worsens.”

Researchers utilized eDNA to study the reef’s microbial community. 

This genomic method required collecting reef water samples, where there are about a million microbial cells per milliliter, and arranging the microbial DNA in the samples to pinpoint microorganisms. 

This allows scientists to gather near real-time information noninvasively regarding the reef’s state. 

“Understanding the composition of a healthy reef microbial community is important. Without the balance of micro and macroorganismal health, you cannot have a healthy functioning ecosystem,” said Becker.

“Another benefit to this advancement is for coral reef restoration efforts. The microorganisms can provide an assessment of the ecosystem health. This could complement visual assessments to determine if a reef’s health has been restored.”

This study was supported by The Tiffany Foundation, NOAA, WHOI Ocean Ventures Fund, the National Science Foundation and WHOI’s Reef Solutions Initiative.

Article Citation: eDNA methods give a real-time look at coral reef health. (n.d.). ScienceDaily. https://www.sciencedaily.com/releases/2024/04/240405231733.htm

Image Citation: Dive Deep Into 50 Amazing Coral Reef Facts. (2021, April 23). Facts.net. https://facts.net/coral-reef-facts/