A New World for Microbes
Investigating the Plastisphere
Former Sea Grant fellow Austin Gray is exploring what happens when microbes meet microplastics.
Billions of microplastic particles make their way through North Carolina’s waterways and into the Pamlico Sound alone each year — which makes understanding the impacts of plastic pollution more important than ever before.
“Due to the prevalence and persistence of microplastics, they present a unique opportunity to investigate an emerging research question,” says Virginia Tech’s Austin Gray. “Do microplastics alter ecosystem processes in their respective habitats?”
Gray, professor of aquatic toxicology, recently received a National Science Foundation Faculty Early Career Development Program grant to investigate microorganisms’ interactions with microplastics in the “plastisphere” — the community of microbes that live on and feed on plastic debris.
Before joining Virginia Tech, Gray earned his master’s at The Citadel and Ph.D. at University of North Carolina Greensboro, conducting groundbreaking work for both degrees with support from Sea Grant, research that included a joint fellowship with the NC Water Resources Research Institute.
“I have been very interested in understanding the ecological implications of pollutants,” he says, “in a sense combining my past research focuses to explore relatively uncharted territory.”
The plastisphere poses a potential threat to the natural carbon cycle — the process by which carbon moves through the environment. Most of the time, rocks, sediments, and living creatures lock away carbon. When organisms expel waste or die, the decomposition process releases stored carbon back into the atmosphere.
Microbes play an important role in the carbon cycle, because they feed on the waste and detritus, preventing that carbon from entering the atmosphere, and, in turn, contributing to the regulation of global temperature. However, Gray says microbes have begun latching onto plastic waste in water, too.
“The microbes or biofilms that colonize plastics may utilize plastic-derived organic matter,” he explains. “Since plastics contain various additives and chemicals used in their production, the question arises: is the dissolved organic matter from plastics inhibiting or stimulating microbial activity and processes?”
Gray says that although his lab has yet to start gathering data for his NSF CAREER project, researchers previously have shown that certain microbes actually prefer the surface of plastics over other natural items.
“This has significant implications for microbial community structure and function in freshwater ecosystems,” he says, “particularly in rivers where plastics can be captured and retained for weeks to years.”
What happens if microbes use microplastics as a carbon source instead of naturally-occurring organic matter?
In addition to potential impacts on global temperatures, according to the International Institute for Sustainable Development, even small increases in carbon concentration in lakes and other small freshwater ecosystems carry a range of detrimental effects. Carbon dioxide is acidic, for instance, and smaller species, such as crayfish, are more sensitive to shifts in pH levels. In some cases, this can lead to local extinction of affected species.
The loss of small species, in turn, can have a cascading effect, as larger species that used to feed on them now must seek out other sources of food, unbalancing the ecosystem. Excess carbon in the water also promotes algae blooms, which can deplete the oxygen supply, leading to fish kills. In some cases, algae can also be toxic both to aquatic life and humans.
While Gray and his team are focused on observing naturally occurring microbes, researchers at NC State are investigating whether designing a microbe with a greater appetite for plastic could be a viable solution to removing PET plastic contaminants from ecosystems altogether. Clearly, a better understanding of the relationships between plastics and microbial communities will be key to understanding the impacts of plastic pollution — and uncovering potential solutions.
“It’s a relatively new world for microbes,” Gray told Virginia Tech News, “and we don’t know what that means for aquatic environments and various processes that take place in them.”
From Austin Gray’s Lab
“Insights into the in-situ degradation and fragmentation of macroplastics in a low-order riverine system” in Environmental Toxicology and Chemistry
More on Austin Gray
Plastic from the NC Mountains to the Sea
Breaking Systemic Barriers: Being Black in the Aquatic Sciences
Researcher measures microplastics’ massive changes on the micro world
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Lily Soetebier is a contributing editor for Coastwatch. She is pursuing an M.S. in technical communication at NC State University.
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