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You do not have to look far to see that we descended into the Anthropocene, a period dominated by the human impacts on this planet – our moving mountains and waterways, our climate corruption, the traces of nuclear material in the geological archives. . Add to this microplastic pollution, an increasingly omnipresent threat that swirls in the ocean and spreads to distant corners of the Arctic.
Today in Progress of scienceresearchers at the Scripps Institution of Oceanography report how the Earth itself is soiled with microplastic particles. By taking a central sample of sediments off the south coast of California, scientists have been able to observe the evolution of plastic concentrations from year to year. And exponentially: Since the 1940s, when plastic production began to take off, microplastic deposition rates have doubled every 15 years. This parallels both the plastic manufacturing figures and the growth of California's coastal population, and leads to a disturbing conclusion: while seaside towns continue to flourish, the amount of microplastics flowing into the sea, contaminating whole ecosystems.
The researchers collected their sediment samples in a core, essentially a giant cookie cutter that cuts layers of several years on the seabed. Back in the laboratory, they dried each layer and passed the material through filters to isolate the particles, which they visually counted under the microscope and chemically tested to determine the variety of plastics.
Interestingly, two-thirds of the particles discovered by the researchers were fibers. These come largely from synthetic clothing such as yoga pants, which remove the fibers during washing. A wastewater treatment plant processes this water before it is pumped out to sea but is not equipped to dispose of all microfibers. "There is just this constant attack of microfibers reaching the bottom of the ocean," said Jennifer Brandon, Scripps oceanographer, lead author of the new paper. "Microfibres for an animal as small as plankton can act like a rope for us: they can entangle them, they can get caught in the guts, they can somehow pinch the limbs."
In addition, macroplastics, such as single-use bags, float over the sea and cook in the sun, causing them to break into much smaller fragments that then swirl in the water column. Then it's only a matter of time before the oceanic organisms ingest the particles – the giant larvae, for example, depend on a trickle of mucus to catch a tiny prey, a stained line of microplastics. Once they have thrown their nets of mucus, the apparatus sinks on the seabed, also causing the plastics to sink down. And this is just one of the ways in which microplastics can move up and down the water column and settle in the mud.
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