Coral reefs are immensely productive and biodiverse, providing habitat for an estimated 25% of marine life. Reef biodiversity encompasses not only the charismatic megafauna that depends on the ecosystem, but also a host of microscopic organisms, many of which play a role in coral health. In addition to photosynthetic zooxanthellae, corals form symbiotic relationships with bacteria, archaea and other microbes that aid the coral with nutrition and growth, mitigation of toxic compounds or stress, early life development and pathogen control. Recent research suggests symbionts might even play a role in photosensitivity and a coral's reaction to oxybenzone-based sunscreens.
The stresses on corals from climate change, ocean acidification, overfishing and other threats disrupt the entire coral reef holobiont. News stories over the last few decades report significant loss in coral reefs and describe sobering bleaching events associated with corals ejecting their symbionts. "This also has a devastating effect on the human communities who depend on the reef for sustenance, ecotourism or storm protection," said Dr. Christina Kellogg, who leads the U.S. Geological Survey's (USGS) coral microbial ecology laboratory.
"If we don't get a handle on tropical coral diseases, when those corals die, those coastal communities lose protection from storms, which then becomes an issue of human life and property. With the deep-sea corals, this is part of a fundamental baseline description of their biology," she explained. Baseline data of healthy coral reefs can even provide insight into the effects of catastrophic events like oil spills. After the Deepwater Horizon spill in 2010, Kellogg had one of the few deep-sea coral microbiome datasets available, and she will soon revisit the Gulf of Mexico to assess the event's ecological impact compared to reference sites.
Conservation Requires Collaboration
To protect coral communities, a collaborative approach that includes residents who depend on the ecosystem is critical, according to Dr. Rosie ʻAnolani Alegado, Director of the Sea Grant Ulana 'Ike Center of Excellence and associate professor of oceanography at the University of Hawai'i at Mānoa. Alegado collaborates with coastal communities in Hawai'i and American Samoa to study how varying exposure to runoff and sewage impacts the microdiversity and ecosystem functioning of watersheds. Identifying problems like nutrification or increases in harmful microbes like Enterococcus helps protect oceans receiving wastewater and the residents relying on water resources. To accomplish this, Alegado engages Indigenous communities and local groups before the project even begins, ensuring they are integral partners in the study from co-design through conclusion and future management. With support from the National Oceanic and Atmospheric Administration (NOAA), Alegado and partners developed a set of best practices and recommendations on building just and generative relationships between researchers and communities.
"My partnerships are relational, not transactional," Alegado said. "The places where I do work are more than just field sites-they are homelands," which, she notes, are often managed by the community members who can mutually benefit from scientific collaboration. "As a researcher, I can't be there all the time. The data I collect are snapshots. Community members can provide ongoing observations of the system. By partnering with them versus just consulting or informing, the design of my research is better, safer and possibly more relevant."
The Power of Data Sharing
Data sharing on a global level can make a big difference. With assistance from a network of scientists, University of Derby's Dr. Michael Sweet and Professor Raquel Peixoto of King Abdullah University of Science and Technology in Saudi Arabia established the Beneficial Microbes for Marine Organisms (BMMO) network to facilitate global collaboration. BMMO began on social media in 2017, with a single tweet asking anyone working with bacteria associated with corals in their labs to document what was cultured, where it was collected from and whether the sample was viable. Sweet's Twitter page has now grown to more than 11,000 followers and resulted in an online, open access list of bacteria in labs around the world that can be freely shared.
"We hope that our centralization of the current state of play of the cultural fraction of bacteria from a coral host will give everyone a helping hand to start their work," Sweet said. "A significant amount of time and money can be spent on the initial processes of culturing microbes, and we have shown what can be possible-speeding up the science to produce something tangible that can be used on reefs."
Robust funding for climate research is essential to understanding the potential impacts of climate change on corals and their symbionts. The loss of coral systems because of climate change and altered microbiota will have devastating, cascading impacts on biodiversity as well as on the human coastal communities who rely on them. Integrating corals and their associated microbiome into climate change models is necessary to understand the full impact of ocean warming on marine life. As scientists continue to explore the connection between coral microbiomes and a broad spectrum of important issues, such as climate change, support for scientific research at NOAA, USGS and other federal science agencies will be crucial.
