eDNA method allows real-time observation of coral reef health

The human intestine is full of microorganisms. Some microbes can make people sick, while others play a role in keeping gut health in balance. But humans aren't the only species whose health depends on these microbes. Coral reef ecosystems rely on microorganisms to recycle organic matter and nutrients. These cells also serve as food for corals and other organisms that depend on coral reefs.

WHOI researchers surveyed eight coral reefs in the U.S. Virgin Islands over a seven-year period, including periods of disruption due to hurricanes and coral diseases, to study microbes in the reef water.

“Coral reefs have been in decline for decades, with climate change, hurricanes, disease, and other stressors playing major roles,” said the study's lead author, a recent author from the MIT-WHOI joint program. said Cynthia Becker, alumnus of.

“Coral reefs provide habitat for approximately 25% of all marine life, but they also support billions of tourists and fisheries. It is important for us to monitor changes in coral reefs over time. That's important, and the microbes in the reef environment really help with that.” ”

The study: “Microorganisms uniquely capture and predict the effects of stony coral tissue loss disease and hurricane disturbance on coral reefs in the U.S. Virgin Islands.'' environmental microbiologydescribes the effects of coral reef disturbance on microorganisms.

During the two major events studied, Hurricanes Irma and Maria in 2017 and the Stony Coral Tissue Loss Disease outbreak that began in 2020, ammonium concentrations in water increased and Prochlorococcus bacteria increased to 34%. %Diminished. Prochlorococcus is a small photosynthetic bacterium that not only brings new carbon to the coral ecosystem and supports coral health, but also produces oxygen for the atmosphere.

“Much of the way we study coral reefs is done at the macro-organism level. But changes in coral and fish communities can go unnoticed for months or even years. “This makes it difficult to track the health of these fragile coral reefs in real time,” he said. Amy Aprile, WHOI microbial ecologist and corresponding author of the study.

“Microorganisms are the hidden engines of coral reefs, growing rapidly and responding to nutrients, temperature, pH, and other conditions. By sampling water, we can see the immediate effects of disturbances and identify potential We can intervene and support coral reefs before the situation gets worse. ”

The researchers used eDNA to analyze the microbial communities of coral reefs. The genomic technique involved collecting a sample of coral reef water, which contains about 1 million microbial cells per milliliter, and sequencing the microbial DNA in the sample to identify the microorganisms. This allows scientists to collect near real-time information about the health of coral reefs in a non-invasive way.

“It is important to understand the composition of a healthy coral reef microbial community. Without a balance between microbial and macrobial health, we cannot maintain a healthy functioning ecosystem,” Becker said.

“Another benefit of this progress is in coral reef restoration efforts. Microorganisms can provide an assessment of ecosystem health, which provides a visual aid to determine whether reef health has recovered. It has the potential to complement assessments.”