Every year, 8m tons of plastic enters the ocean. Images of common household waste swirling in vast garbage patches in the open sea, or tangled up with whales and seabirds, have turned plastic pollution into one of the most popular environmental issues in the world.
But for at least a decade, the biggest question among scientists who study marine plastic hasn’t been why plastic in the ocean is so abundant, but why it isn’t. What scientists can see and measure, in the garbage patches and on beaches, accounts for only a tiny fraction of the total plastic entering the water.
So where is the other 99% of ocean plastic? Unsettling answers have recently begun to emerge.
What we commonly see accumulating at the sea surface is “less than the tip of the iceberg, maybe a half of 1% of the total,” says Erik Van Sebille, an oceanographer at Utrecht University in the Netherlands.
“I often joke that being an ocean plastic scientist should be an easy job, because you can always find a bit wherever you look,” says Van Sebille. But, he adds, the reality is that our maps of the ocean essentially end at the surface, and solid numbers on how much plastic is in any one location are lacking.
It is becoming apparent that plastic ends up in huge quantities in the deepest parts of the ocean, buried in sediment on the seafloor, and caught like clouds of dust deep in the water column.
Perhaps most frighteningly, says Helge Niemann, a biogeochemist at the Royal Netherlands Institute for Sea Research, it could fragment into such small pieces that it can barely be detected. At this point it becomes, Niemann says, “more like a chemical dissolved in the water than floating in it”. [Continue reading…]