Any floating object in the ocean tends to attract life; fishermen know this and deploy floating buoys to concentrate fish for harvesting.

Plastic marine debris is no different and, at microscopic scales, microbes such as bacteria, algae, and other single-celled organisms gather around and colonize plastic and other objects floating in water. Even small pieces of plastic marine debris the size of your pinky nail can act as microbe aggregating devices.

“We call this community of microbes growing as a thin layer of life, a biofilm on the outside of plastic, the ‘plastisphere,’ analogous to the layer of life on the outside of planet Earth called the ‘biosphere,’” said Dr. Erik Zettler of Sea Education Association of Woods Hole.

Zettler will give an illustrated lecture on The Plastisphere: A New Marine Ecosystem Tuesday, April 15, at 7 p.m. at Camden Public Library, as part of the library’s Maritime Month series. Maritime Month is supported in part by Maine Boats, Homes & Harbors magazine.

“Using plastic samples collected during Sea Education Association student research cruises, we are studying what kinds of microbes live in the plastisphere, how they colonize the surfaces of plastic, and how they might affect marine ecosystems,” he said.

Plastic is now the most common form of marine debris and there is substantial public and scientific interest in this issue. Other than the known problems of entanglement and ingestion by fish, turtles, birds, and marine mammals, there are questions of contaminant transport and invasive species that could affect native communities and aquaculture operations. The microbial community that develops on plastic marine debris has been particularly poorly studied, but could play a role in nutrient cycling, plastic degradation, and the spread of potentially harmful microbes. SEA students from colleges across the country have played a major role in plastic marine debris research, collecting and analyzing the most extensive data set on plastic marine debris in the world, with more than 10,000 individual net tows in the Atlantic and Pacific oceans since the 1980s.

There is a lot of plastic in the ocean, but intense public attention has encouraged a certain amount of media hype that creates misperceptions about the problem. SEA’s extensive data set allows student scientists to objectively examine and characterize the distribution and quantity of plastic in different parts of the ocean including the so called “Pacific Garbage Patch.”

Zettler is a microbial ecologist and oceanographer who has been a member of the Woods Hole scientific community for many years, having worked for nine years as a Research Associate in the Biology Dept. at Woods Hole Oceanographic Institution before joining SEA in 1994. As associate dean of Institutional Relations and Research, Zettler works with faculty and administrators at other academic institutions to describe the unique off-campus study opportunities in marine studies that SEA courses provide to students from all academic disciplines. In addition, he coordinates research collaborations with students, faculty, and scholars interested in data, samples, or ship time on SEA voyages. He has participated on over 50 research cruises on SEA and UNOLS vessels and has done field work in Antarctica, Bermuda, Canada, Costa Rica, Spain, and USA. Whenever possible, he teaches in the field including on board the SEA vessels in the Atlantic and the Pacific. His most recent project is studying the microbial community that develops on plastic marine debris and he is part of the multi-institutional team in Woods Hole that first described and coined the term “Plastisphere”.

In an online Smithsonian article, Zettler describes the results of his research. “Scanning electron micrographs reveal a complex geography of microbial life on the cracked and pitted surfaces of plastic pieces that have been aging and weathering in the ocean. Tracy Mincer, a scientist at Woods Hole Oceanographic Institution studying this new community, refers to it as a ‘microbial reef’ because it is a complete ecosystem with primary producers (like plants), grazers, predators, and decomposers, just like the community of larger organisms found on the complex surface of a coral reef. One of our most interesting discoveries is a type of cell that we call ‘pit formers,’ spherical cells that appear to be embedded in the surface of the plastic pieces. These may somehow contribute to the breakdown of plastic marine debris, which would have implications for what happens to plastic in the ocean over the long term.”