Impact of coral chemical compounds on reef health
Stumbling upon a new source of underwater caffeine was just an added bonus of a new study examining the impact of chemical compounds that corals release into the seawater.
The study found that the organic chemical compounds produced through metabolism — known as metabolites or exudates — vary significantly by coral species, and that the compounds impact the abundances and compositions of reef microorganisms differently.
This differential release of metabolites from benthic reef organisms is particularly significant in the Caribbean, where coral dominance is shifting from hard stony corals to soft octocorals in response to human-caused stressors such as eutrophication, overfishing and global climate change.
The study "demonstrates the importance of benthic exudates for structuring microbial communities on oligotrophic reefs by focusing on the exudates released from abundant stony corals, octocorals, and an invasive alga," according to the paper led by authors at the Woods Hole Oceanographic Institution and published in ISME Communications.
Here's the caffeine connection.
For the study, researchers collected exudates from six species of Caribbean benthic organisms in a lab setting, using organisms obtained from within the Virgin Islands National Park, including stony corals, octocorals, and an invasive encrusting alga called Ramicrusta textilis. The researchers surprisingly found that R. textilis released caffeine in high quantities.
As to why R. textilis produces caffeine, the study notes that caffeine production has not been widely investigated for marine organisms, but that it is a common metabolite produced by land plants generally to deter herbivores and pathogenic microbes.
This study "is an important step forward in identifying chemical signals that can help scientists assess reef health," said Elizabeth Kujawinski, co-author of the paper. "Similar to human health diagnostics, the chemical signals in a reef ecosystem are linked to the functions of the symbiotic relationships within reefs." Kujawinski is director of the Center for Chemical Currencies of a Microbial Planet, a U.S. National Science Foundation Science and Technology Center based at WHOI.
Co-author Amy Apprill of WHOI said an important implication of the research is that a diverse benthic community likely supports a more diverse microbial community.
"Metabolites are produced by all organisms during normal functions such as digestion and reproduction, and in removing waste products," said Elizabeth Canuel, a program director in NSF's Division of Ocean Sciences. "This research provides new insights into the composition of this relatively unknown group of chemicals produced by reef organisms, which could provide valuable information about the health and function of coral reef ecosystems."