A new study has analyzed the microbiome of a coral species before, during and after a period of “dormancy” during cold temperatures. The research is published in Applied and Environmental Microbiology.
It’s “breeding” time for the northern star coral
Winter is approaching, which means many creatures on Earth are preparing for hibernation, a period of rest that allows for energy conservation and survival in adverse weather conditions. On land, small mammals such as squirrels and hedgehogs seek safe burrows and hiding places for their long-term naps.
Under water, a species of coral – Astrangia cupulata – also known as the “north star coral” similarly experiences a period of quiescence, providing a seasonal reset. Found in arctic waters, A. poculata it retracts its tentacles, stops eating and becomes dormant when the water temperature drops.
“Dormancy, at its most basic, is a response to environmental stress, in this case, cold stress,” says Dr. Anya Brown, assistant professor of evolution and ecology and member of the Bodega Marine Laboratory at the University of California, Davis. (UC Davis). “Understanding more about this recovery period could help us understand which microbes may be responsible for coral recovery in warmer tropical systems.”
Brown is the lead author of a new study that asked: What happens to the coral microbiome while it is dormant? The research, conducted in collaboration with Woods Hole Oceanographic Institution (WHO) and Roger Williams University, is the first to characterize wild coral microbiomes before, during and after quiescence.
Coral microbiome “reorganizes” during rest
The scientists used 16s rRNA gene sequencing, a commonly adopted tool for studying the microbiome. From October 2020 to March 2021, they dove 60 feet into the cold waters of a pier in Woods Hole, Massachusetts, to collect 10 different colonies of A. poculata, which were then sequenced upon return to the laboratory.
Brown and colleagues found that while the coral “sleeps,” it removes copiotrophic microbes, including putative pathogens. During and after quiescence, the scientists identified an increase in bacteria and archaea that are associated with nitrification, perhaps in response to the coral not eating during dormancy. “We have long hypothesized this A. poculata’s seasonal dormancy allows the coral microbiome to reset and restructure,” says co-author Dr. Koty Sharp, associate professor at Roger Williams University. “Our research found evidence of a change during this dormant period that we may help identify microbial associates that are key to coral health and recovery from disturbance.”
“This work opens up a lot of questions,” adds Brown. “One of the big ones is: Why do coral ‘wake up’ in early spring? This study suggests that key microbial groups may play an important role in triggering the emergence or emergence of dormancy in “this coral and the regulation of its microbiome”.
The predictability of A. poculata’s dormancy offers a natural manipulation system to “further identify the factors that regulate host-microbial associations,” the authors conclude in the paper.
reference: Brown AL, Sharp K, Apprill A. Shuffling of the coral microbiome during dormancy. AEM. 2022;0(0):e01391-22. doi:10.1128/aem.01391-22.
This article is a rework of a Press release issued by University of California, Davis. The material has been edited for length and content.