The Plastisphere: an interview with Dr. Erik Zettler

Dr. Zettler is a Visiting Scientist in the department of Marine Microbiology and Biogeochemistry at the Royal Netherlands Institute of Sea Research. His research interests include the ecology of plastic marine debris, microbial ecology, and plankton community structure. He is one of several scientists involved in the Plastisphere segment of research for The Swim.

Scientists estimate that 5 to 12 metric tons of plastic enters the ocean from land each year. This waste then breaks down in the water via physical and chemical processes into millimeter-sized particles called microplastics. In the Northern Pacific, ocean currents can trap high concentrations of microplastics in plastic accumulation zones.

In some of these zones, like the Great Pacific Garbage Patch, their concentration may reach up to 1 million particles per square kilometer. The danger these particles and larger pieces of waste pose to marine life like fish, birds, turtles, and marine mammals is of significant public and scientific interest. However, the diverse community that forms on and around microplastics- referred to as the “Plastisphere”- is just now beginning to be studied by scientists like Dr. Erik Zettler.

Can you tell us more about the research you’ll be doing with The Longest Swim?

Along with my colleagues Dr. Linda Amaral-Zettler at the Marine Biological Laboratory in Woods Hole, MA, as well as Dr. Tracy Mincer at Woods Hole Oceanographic Institution, we’re working on a project that we call the “Plastisphere”. Just like the biosphere is the thin layer of life on our planet, we came up with the word “plastisphere” for the life that attaches to any piece of plastic in the ocean.

We’re interested in that for a number of reasons. One is just straight scientific curiosity in ecology: what organisms are living on this new man-made substrate out in the ocean? We’re also interested in it from a practical point of view: how are the microbes and animals that colonize the plastic affecting it? Are they breaking it down? Are they making it sink? And also from an oceans and human health point of view, are pieces of plastic potentially transporting either disease-causing organisms or organisms that could cause harm? There are other people around the world working on these questions but it’s a pretty new topic, so we’re very excited to learn more about this community.

How often can the crew expect to encounter these marine plastics?

Well, ideally they will be able to take samples every day. Considering the swim’s route I expect them to have plastic in their samples most of the time, with a day here or there when the boat will be outside the real concentration zone. Models of the Pacific actually show plastics accumulating in an eastern area and a western area within the larger convergence zone, but once they enter the concentration zone they’ll have multiple pieces each day.

Obviously this plastic isn’t naturally occurring- it’s coming from humans. What kind of impact does the presence of these particles have on ocean life, the environment, and us?

That’s a good question and unfortunately we don’t have the answer to it. Plastic is a man-made product, it potentially carries toxic compounds with it, and we know of certain impacts like causing harm to animals when ingested. There are still a lot of impacts we don’t know about. For instance, when really small pieces of plastic are eaten by smaller and smaller organisms, are the chemicals in the plastic being passed up the food chain? So there’s a lot we don’t know about the impact of plastic in the ocean from a microbial point of view.

Any time you put a surface in an aquatic medium bacteria will attach to it and the metabolism of that area of the ocean increases. It concentrates nutrients, so the question – if a lot of pieces of plastic are out there – is if the metabolisms of the organisms on those plastics affects secondary nutrients and the metabolism of the ocean. These are all questions that we don’t know the answer to.

And the samples that The Swim collects will be able to help answer those questions?

The data that The Swim is going to provide will be pretty awesome. They’re going to be collecting a unique data set in that they’ll be sampling at a high resolution every day, or every other day, all the way from Japan to San Francisco. I don’t know that there’s another data set like that, so that’s very important.

The plastics they collect will also be preserved so that we can extract DNA to see the whole community of microbes living on a little piece of plastic the size of your fingertip. We’ll also be able to look at the seawater they’ve collected because we want to know if what’s living on this debris is really different from what’s living out in the water. Ideally we’ll be able to track both the communities living on the plastic and in the water all the way across the Pacific Ocean, with The Longest Swim’s help.

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