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Recent research has unveiled the significant chemical diversity of substances produced by coral reefs, revealing that thousands of distinct chemicals from tropical corals and seaweeds are available for microbial decomposition and utilization. This study, published in the journal Environmental Microbiology and conducted by an international team led by scientists from the Scripps Institution of Oceanography (SIO) and the University of Hawai’i (UH) at Manoa, offers valuable insights into the complex interactions among coral reefs, marine microorganisms, and the carbon cycle.
In vibrant ecosystems like coral reefs, especially in nutrient-poor environments, very little material goes to waste. Microorganisms play a pivotal role in decomposing, recycling, and transforming the remnants left by other organisms.
“We already knew that certain substances released by coral reefs, known as exometabolites, are accessible for microbial metabolism,” explained Craig Nelson, a professor at the UH Manoa School of Ocean and Earth Science and Technology. “However, our research has revealed that the diversity and quantity of exometabolites that microbes can exploit is much greater than previously recognized, encompassing hundreds of compounds across various chemical classifications.”
“We were particularly astonished to find that exometabolites from chemical classes once thought to be challenging for microbes to decompose—such as those with benzene rings, terpenoids, and steroids—could actually be utilized,” stated Zachary Quinlan, the study’s lead author and a postdoctoral researcher at the Hawai’i Institute of Marine Biology in SOEST. “These findings illustrate a dynamic landscape of ecosystem contribution to bioavailable substances and their implications for microbial metabolism, which is crucial for carbon cycling in coastal marine ecosystems.”
The Carbon Cycle and Resilience of Coral Reefs
The collective amount of dissolved organic material in oceans, which includes the chemicals released by coral reefs, holds a carbon quantity comparable to atmospheric carbon dioxide levels. Therefore, the way microbes interact with this organic matter significantly impacts the global carbon cycle.
Shifts in the types of organisms inhabiting a reef, such as the transition from stony corals to fleshy seaweeds, also lead to changes in seawater chemistry. Alongside their examination of what chemicals are emitted from reef organisms, the research team conducted experiments to analyze whether microbes showed a preference for substances from stony corals versus those from seaweeds.
“Our observations indicate that coral and algae can selectively support the proliferation of specific microbial communities by releasing unique chemicals that cater to particular microbial types,” noted Linda Wegley Kelly, the study’s senior author and an associate researcher at SIO. “These results underscore the potential for shifts from coral-dominated to algae-dominated reefs to disrupt ecosystem functions and jeopardize the resilience of these systems, potentially increasing their vulnerability to disease or bleaching.”
Looking ahead, the research team plans to further explore how these chemical characteristics can inform coral reef management strategies and enhance the success of coral restoration efforts.
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