You donât have to look far to see weâve descended into the Anthropocene, a period dominated by human impacts on this planetâour moving of mountains and waterways, our corruption of the climate, the traces of nuclear material in the geological record. Add to all that microplastic pollution, an increasingly pervasive threat thatâs swirling in the ocean and finding its way to distant corners of the Arctic.
Today in Science Advances, researchers at the Scripps Institution of Oceanography report how the Earth itself is tainted with microplastic particles. By taking a core sample of sediments just off the coast of Southern California, the scientists could observe in its layers how plastic concentrations have changed year after year. And exponentially so: Since the 1940s, when plastic production began to take off, microplastic deposition rates have doubled every 15 years. This correlates with both figures on plastic manufacturing and coastal population growth in California, and brings us to a troubling conclusion: As seaside cities continue to boom, so does the amount of microplastic flowing into the sea, tainting whole ecosystems.
The researchers got their sediment samples from something called a box core, essentially a giant cookie cutter that slices down many yearsâ worth of layers in the seafloor. Back at the lab, they dried each layer and ran the material through filters to isolate the particles, which they counted visually under a microscope and tested chemically to determine the variety of plastic.
Interestingly, two-thirds of the particles the researchers found were fibers. These are coming largely from synthetic clothing like yoga pants, which slough off fibers in the wash. A wastewater treatment plant processes that water before pumping it out to sea, but isnât equipped to remove all the microfibers. âThere's just this steady onslaught of microfibers reaching the bottom of the ocean,â says Scripps oceanographer Jennifer Brandon, lead author on the new paper. âMicrofibers for a tiny animal like plankton can act like a rope would for usâthey can entangle them, they can get caught in their guts, they can kind of pinch their limbs.â
In addition, macroplastics like single-use bags float out to sea and bake in the sun, causing them to break into much smaller fragments that then swirl in the water column. Then itâs only a matter of time before ocean organisms ingest the particlesâgiant larvaceans, for instance, rely on a mucus net to catch tiny prey, a haul now sullied with microplastics. Once they discard their mucus nets, the apparatus sinks to the seafloor, dragging the plastics down as well. And thatâs just one way microplastics can move up and down the water column and settle in the mud.
Then thereâs the question of color, which is often overlooked in research on plastic pollution. Although microplastics come in a galaxy of hues, Brandon and her colleagues found that most of their particles were white. Many marine predators choose their prey based on color, so they could be mistaking white microplastic particles for, say, a transparent planktonic organism with eggs in its belly. âIt's happening and we're not talking about it enough, that's for sure,â says Brandon.
The tricky bit about microplastic pollution is that little is known about how the pollutant might be affecting organisms, and in turn whole ecosystems. Itâs virtually impossible to do a controlled study out in the sea. (Though researchers may soon use remote lakes in Canada to do experiments.) And when scientists are working in the lab, theyâre exposing organisms like bacteria to unnaturally high concentrations of plastic to elicit a physiological response.
The concentration of microplastics off the coast of California, where these Scripps researchers did their work, might even be relatively low compared to other parts of the world, making it harder to observe their effects on organisms. âIf they were doing the same thing in the Yellow Sea in China, right outside some of the big rivers like the Yangtze and Yellow River, the concentrations would probably be huge and cause adverse effects,â says University of Michigan eco-toxicologist Allen Burton, who studies microplastics.
Whatâs particularly troubling is that as coastal populations continue to grow in China and elsewhere, plastic will continue to pile up in the sea, be that by litter or tainted wastewater. At the same time, plastic production is skyrocketingâhumans made 400 million tons in 2015, and thatâs expected to double by 2025.
All that plastic doesnât easily degradeâit is, after all, engineered to be tough. âThey will still be in sediment cores for future civilizations to find them, because except for bacteria it doesn't look like most things can degrade them in any way,â says Burton. âThey break down into smaller and smaller pieces but they're still inherently, chemically plastic. We'll find them like we find old artifacts.â
So given its omnipresence and its ability to persist in the environment, is microplastic a good marker for the Anthropocene, humanityâs era of extreme environmental meddling? âWhy wouldn't it be a good marker,â says Burton, âif plastic started in the mid-â40s and we've got all the numbers for plastic production and we know how it's going up?â
Welcome to Planet Plastic. This is our shameful environmental legacy.
- We can be heroes: How nerds are reinventing pop culture
- Why on earth is water in Hawaii's Kilauea volcano?
- Jeffrey Epstein and the power of networks
- I replaced my oven with a waffle maker and you should, too
- Learn how to fall with climber Alex Honnold
- đ Facial recognition is suddenly everywhere. Should you worry? Plus, read the latest news on artificial intelligence
- đđœââïž Want the best tools to get healthy? Check out our Gear teamâs picks for the best fitness trackers, running gear (including shoes and socks), and best headphones.