Scientists study ‘plastisphere,’ its role in ocean

Sea Education Association students monitored a net in the ocean. “Plastic is the major form of debris in the ocean,” said the group’s associate dean, Erik Zettler.

Sea Education Association students monitored a net in the ocean. “Plastic is the major form of debris in the ocean,” said the group’s associate dean, Erik Zettler.

By Carolyn Y. Johnson  |  GLOBE STAFF   |   JULY 15, 2013

Scientists have probed the diversity of life in all sorts of ecosystems, from the insides of our guts to the sediments beneath the ocean floor. Now, a small group of Massachusetts scientists is eyeing a new frontier: the flotilla of tiny pieces of plastic adrift on ocean surf.

A new study describes the “plastisphere” — the microbial communities that hitch rides on the confetti-sized bits of plastic that litter ocean waters. The authors discovered a thriving, miniature world aboard the microplastic “reefs,” where communities of bacteria and other microbes create energy from sunlight, reproduce, and prey on one another.

Researchers at three Woods Hole-based institutions worked together to try to better understand what role these tiny bits of plastic play in the larger ocean ecosystem.

Among their discoveries, reported in the journal Environmental Science and Technology, is the surprising finding that the microbial communities are distinctly different from the ones in nearby ocean water.

And at least one kind of plastic was dominated by a member of a group of bacteria commonly associated with various diseases, including cholera. They could not tell exactly which species was present and plan to do further studies to try to hone in on its identity.

“The thing that impressed me the most is that it is a little world unto itself,” said Linda Amaral-Zettler, an associate scientist at the Marine Biological Laboratory, a research institution based in Woods Hole. “How does it ultimately affect organisms eating it — and ultimately us? We eat shellfish and fish. . . . I think there’s a much broader issue here that’s come to our attention.”

Scientists took two cruises: one that set out eastward from Bermuda in 2010 and another that departed St. Croix in the US Virgin Islands and sailed to Woods Hole in 2012. They threw a net to skim the ocean’s surface and retrieve hundreds of tiny bits of plastic. They performed DNA analysis and used an electron microscope to analyze the life on the plastic, and used a kind of analysis called spectroscopy to figure out the chemical composition of the plastic.

The scientists hope that the study can begin to shed light on how plastic contributes to the ocean ecosystem. Plastic has particular properties that make it an interesting ocean substrate — microbes can stick to its surface, and it tends to originate and spend time in coastal waters where runoff and waste enter the ocean.

That, combined with the fact that it sticks around in the environment, means that it might be playing an ecologically significant role in ferrying bacteria around the ocean.

The scientists are now trying to understand exactly which pathogens dwell on sea plastic, and what role, if any, these microbes could play in marine and human health.

“Plastic is the major form of debris in the ocean,” said Erik Zettler, associate dean of the Sea Education Association, a nonprofit focused on ocean education based in Woods Hole and one of the authors of the paper.

“It has a very long lifespan, not like a piece of wood or a feather that degrades over months and disappears — plastic persists for years, perhaps decades.”

The researchers are also trying to find out how plastic caught in ocean currents gained its unexpected “plastisphere” in the first place. They are tethering bits of plastic in coastal waters to see what kinds of microbes take up residence on the surface of plastic.

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