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Q&A: Professor Obbard on Microplastics in Sea Ice

By Anna Fiorentino
October 2014 • Thayer By Degrees: PhD

Dartmouth engineering professor Rachel Obbard
Prof Rachel Obbard

Originally published in June in the scientific journal Earth's Future, the discovery by Dartmouth engineering professor Rachel Obbard Th'06 of tiny plastic particles embedded in Arctic sea ice made headlines for weeks afterward. Working with students from Dartmouth's Women in Science Project (WISP)—including Melissa Queen '13, Alexandra Khitun '14 and Ying Qi Wong '14—Obbard came across these pollutants accidentally and determined their most likely sources to be consumer products and packaging, washing machines, and manufacturing.

How did you discover microplastics in sea ice?

One of the things that people don’t realize about sea ice is how porous it is. This is important for many reasons, the climate for example. One of the things I'm interested in as a sea ice scientist is the microhabitat found in the pores in the base of sea ice. There is actually an algal community there, enough so that the basal layer is noticeably brownish-green, especially during algal blooms when the sun rises in the polar springtime. In 2009, when I first decided to take a look at this microhabitat, I began by simply melting and filtering some samples of this ice to see what I could expect for numbers and varieties of marine diatoms, which are tiny single-celled phytoplankton. In addition to the diatoms and some silt and sand, we found brightly colored pieces of plastic in the filters. I sent samples off to Professor Richard Thompson at the University of Plymouth in England who is a leading expert on microplastics and his group used Fourier Transform Infrared Spectroscopy to identify the polymer types in hundreds of individual particles. We found particles of rayon, polyethylene, nylon, polypropylene, polystyrene, polyester and acrylic.

Microplastics in sea ice
Filtered particles from Arctic sea ice. Photo credit: Y.-Q. Wong and A. Khitun/Dartmouth College

What's their effect on the environment?

The overall sea ice cover is becoming thinner in the Arctic as older, multiyear ice is replaced by thinner annual ice. This means that trillions of these microplastic particles that have been locked up in multiyear ice are now being freed in surface water and that in the future they’ll be more available to marine life. The plastic floats initially but over time becomes biofouled and sinks. Microplastics have been found in ocean sediments as well as in surface waters. There are a lot of studies being done on microplastics found in the gastrointestinal tracts and respiratory systems of marine organisms, in mussels and crabs for example. The alarming thing is, not only do the microplastics themselves affect the animals that take them in but some types of plastics also tend to absorb high concentrations of other organic pollutants, which are then transferred to the marine life. The effect of microplastic pollution on the higher food web is something biologists are studying now.

What can we do about this?

First of all, we can stop using toiletries and cleaning products containing polymer beads, including some toothpastes and facial scrubs. We can also clean the filters in our washing machines regularly, avoid flushing hygiene products, and reduce the number of plastic containers we buy. There are some pretty cool and inspiring blogs by people who have gone a year without plastics, but most of us can’t or won’t go that far. We can, however, make a point of reusing them when we can and carefully recycling the rest. People can also get involved in finding out how their municipality disposes of plastics—not all single stream recycling systems are created equal.

Are you conducting any follow-up studies?

Yes, I’m hoping to pull together an international team to conduct a more thorough study of the location, types and ramifications of microplastics across the Arctic. Hopefully this work will help us identify and reduce its primary sources, and raise the level of attention to the problem.

Why do you enjoy working with WISP interns?

I love working with students. Undergraduates are super enthusiastic and hardworking. It's fun to see them gain competency in laboratory research and then in presenting their research. I wish I had had someone at my undergraduate college encouraging me, never mind giving me opportunities and mentoring. Back then it was sink or swim and women were sometimes told that we didn't belong in engineering school. Girls nowadays pretty much believe they can do or be anything, but sometimes sticking with it in the face of cultural pressure is hard. I hope my work with students helps counteract that.

Tags: alumni, climate change, environment, faculty, research, students

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