Even when the sea looks clean, its surface can be flecked with tiny fragments of paint and fiberglass. That’s the finding from a study that looked for plastic pollution in the uppermost millimeter of ocean. The microscopic fragments come from the decks and hulls of boats, and they could pose a threat to tiny creatures called zooplankton, which are an important part of the marine food web.
The discovery is “continuing to open our eyes to how many small synthetic particles are in the environment,” says Kara Law, an oceanographer who studies plastic pollution at the Sea Education Association in Woods Hole, Massachusetts, and wasn’t involved in the study.
The millimeter-thick skin of the ocean, called the sea surface microlayer, differs from the underlying water. Surface tension and sticky secretions from microbes keep tiny particles within this layer. Previously, scientists scanning the ocean for plastic pollution hadn’t looked specifically at this layer. Instead, they’d take bulk samples from the surface microlayer and below. Earlier studies also tended to use coarser nets that don’t capture the tiniest particles.
Researchers led by Won Joon Shim, an environmental chemist at the Korea Institute of Ocean Science and Technology in Geoje-shi, South Korea, focused on the microlayer itself. They collected water samples along the southern coast of Korea, up to 16 kilometers offshore. When they gently touched a sieve with 2-millimeter-wide holes to the surface, water from the microlayer gloms on. Examining the samples in the lab, the researchers found well-known kinds of plastics: polyethylene, polypropylene, and expanded polystyrene. But, to their surprise, these made up just 4% of the particles.
Eighty-one percent of the synthetic particles in the microlayer consisted of alkyds, a binder in paints, the team reported online ahead of print in Environmental Science Technology. Another 11% were polyester resins used in paint and fiberglass.
Old boat image via Shutterstock.
Read more at Science.