MANOA — An invisible and multi-cultural web of bacteria, viruses and biochemicals work together to keep coral colonies healhty, according to a study published in the scientific journal “Frontiers of Marine Science.”
The study was completed by a team from the University of Hawai‘i at Manoa, University of British Columbia and San Diego State University, and was launched to discover specific microbial and viral functions that appear to be key components of the coral microbiome, according to a news release about the study.
Researchers used a combination of state-of-the-art molecular methods and cutting-edge, 3D-imaging techniques to create high-resolution molecular maps of coral-reef organisms. Their work shows that healthy reefs require more than just resilient coral polyps; they require other microorganisms to work together to outcompete with harmful organisms like algae.
“Our recent research extends this work into a spatially-explicit framework, and makes for some really-impressive, 3D molecular maps,” said Ty Roach, Ph.D., study senior author and post-doctoral researcher at the Hawai‘i Institute of Marine Biology in UH Manoa’s School of Ocean and Earth Science and Technology.
“Further, we found that patterns in bacteria and viruses that live on and in corals were mainly driven by ecological factors, such as how close to a competitor the sample was taken.”
The team sampled two coral colonies from a Caribbean coral reef and made 3D reconstructions of the corals and their interacting organisms using a method called structure from motion photogrammetry. Multiple molecular methods were then used to investigate the bacterial and viral DNA, RNA and biochemicals that were associated with these corals. These molecules were then mapped back onto the 3D models.
“The current state of ecology has demonstrated that corals are home to millions of microbes and viruses which exist in a complex biochemical milieu,” said Emma George, co-lead author of the study and doctoral candidate at UBC.
“These viruses, microbes and chemicals in combination with the coral host form a unit called a holobiont. Understanding the roles of each of these players in ecosystem function has become increasingly important as coral-reef health has begun to decline over recent decades.”
The study adds to a growing body of research that indicates coral-reef health is heavily dependent upon the presence and resilience of a multitude of microbes.
One of those studies was detailed in a 2019 paper from the U.S. Geological Survey, looking at at physiochemical controls on zones of higher coral stress where black band disease occurred at Makua reef on Kaua‘i’s North Shore.
In addition to studying what is growing on the reefs, the 2019 USGS paper also considered the nutrients in the water surrounding the coral reefs and how water conditions contribute to the growth of microbes.
“Results reveal localized stagnant water parcels at Makua Reef where groundwater-derived, high-nutrient loading and low salinities act in concert as stressors to coralline health — and where black band disease was uniquely identified.” the paper stated.
Authors further explained they observed high nutrient levels during low-tide conditions that were likely associated with nearby upstream cesspools and drain fields.
Functional and healthy reef ecosystems protect coastlines, contribute to local economies and support marine-food webs, including fisheries. The new findings have direct implications for coral-reef restoration and management, as they provide a more-mechanistic understanding of the way that local stressors affect corals and can lead to disease.
Roach said the insight gained from this work is allowing researchers to design and test probiotic blends and phage therapies (blends of bacterial viruses — phage — that can restructure the bacterial community) for use on corals.
“In this way, we aim to utilize personalized-medicine techniques to help corals gain an ecological advantage over competitors such as harmful algae,” Roach said.
“Additionally, these 3D-molecular-mapping methods could be applied to many other ecologically-important organisms beyond corals,” said Mark Little, co-lead author of the study and doctoral candidate at SDSU. “It is our hope that this combination of methods to generate underwater molecular maps will be a fruitful way for others to better understand the holobiont of many marine animals and plants.”
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Jessica Else, editor, can be reached at 245-0457 or jelse@thegardenisland.com.
