“Seabirds feed on larval fish, adult fish feed on larval fish—it's a prominent food source,” says NOAA oceanographer Jamison Gove, co-lead author on the new paper, published in the Proceedings of the National Academy of Sciences. “So that clearly has implications for how plastics can be distributed and quickly get higher up the food chain.”
Gove and his colleagues dissected hundreds of larval fish and found that 8.6 percent of specimens from slicks—which appear as smooth ribbons on the surface—contained microplastics, more than twice the rate as larvae in nearby non-slick surface waters. Less than 10 percent may not sound like much, but we’re talking about innumerable little larvae out there in the slicks, so that percentage translates into a huge population of tainted organisms.
These larvae don’t yet have fully developed immune systems to deal with ingested microplastics, which is particularly worrisome when you consider that the particles are known to accumulate pathogens like bacteria as they float around the sea. “One possibility is that because larval stages are so vulnerable, eating one piece of plastic could actually potentially kill them,” says NOAA marine ecologist Jonathan Whitney, co-lead author on the paper. It’s possible that far more larvae might be eating microplastics, perishing, and sinking to the bottom of the sea than scientists know.
The larvae might be mistaking plastics for some of their more common foods—other species of plankton that float around on currents. Most of the ingested particles were transparent or blue, the same color as their prey, such as tiny crustaceans called copepods. Nearly all of the consumed microplastics were fibers, from sources like plastic fishing nets, which slough off fibers that resemble the antennae of copepods.