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Microplastics and Our Oceans

Microplastics and Our Oceans

We know already that our plastic love is as deep as the deepest depths of the ocean. Because we found it there, of course, far down on the bottom of Mariana Trench. It takes a special submarine form to make the almost 36,000-feet dive. Yet sweetheart wrappers? Bon voyage.

And while those unwelcome discoveries show just how widespread this plastic plague has become, there may be something even more unsettling about these new deep-sea denizens. Researchers have been unable to account for any of the 8 million tons of it that we have every year into the ocean.

Yet finally a new study would have addressed the question.

Research has found that plastic moves into the deep-sea communities which call home from 500,000 to 10 million species anywhere. But one thing is zip-loc bags between giant spider crabs and tube worms, and vampire squid. Also, plastic finds its way to the vents which literally stir the oceans.

Such slow-moving water masses close to the ocean floor, called thermohaline currents, serve as a massive circulatory network. At these depths they swing around oxygen and nutrients vital to life. They might also spread microplastics far and wide according to the new study.

"Our recent work shows that strong currents sweep these microplastics down the seafloor into large 'drifts' that collect them in enormous amounts," the researchers noted in The Conversation.

The Plastic We Don't See

The terrifying garbage mounds floating on the open sea, like the garbage grandfather, the Great Pacific Ocean Garbage Patch, are easy to find. Yet they resemble more icebergs than islands. When plastic breaks down it becomes smaller, creating particles with a diameter of less than five millimetres. Although some microplastics are still floating, at least half of them sink into the sea, permeating even the food chains there.

"Nearly everyone heard of the infamous floating plastic 'garbage patches' of the ocean, but we were shocked by the high concentrations of microplastics we found in the deep-sea floor," says lead author Ian Kane of Manchester University in a press release.

"We discovered that microplastics are not distributed uniformly throughout the study area; instead they are distributed through powerful seafloor currents that concentrate them in certain areas."

Nonetheless, the vast microplastic drifts that form on the ocean floor can surpass far that which we see on the surface.

Scientists compared sediment samples taken from the Tyrrhenian Sea, off the Italian coast, to those taken deeper down the continental slope for their analysis. Coastal samples yielded 41 plastic parts per spoonful of sediment. The number deeper down the shelf dwindled to nine bits. Yet they find a whopping 190 bits of plastic per spoonful in the sediment built up deep in the ocean, parallel to thermohaline currents — the largest concentration of microplastics detected at seafloor to date.

A Plastic Buffet for Marine Life

Researchers say plastic is likely to be distributed throughout the depths through those deep-sea vents, swishing plastics alongside nutrients and oxygen. Indeed, if plastic has compromised the ocean's circulatory system, it could choke out critical biodiversity bastions on the seafloor.

"We have now discovered how microplastics are transported by a global network of deep-sea currents, creating plastic hotspots inside vast sediment drifts," the scientists note. "By catching a ride on those currents, microplastics may accumulate where there is an abundance of deep sea life."

That means that marine animals, especially microorganisms that are vital to ocean health, get a side order of plastic with their oxygen and nutrients — and that current efforts to clean up the ocean can only literally scratch the problem's surface.

"Our study has shown how detailed studies of seafloor currents can help us connect deep-sea microplastic transportation pathways and find 'missing' microplastics," notes the National Oceanography Center co-author Mike Clare in the press release. "The findings illustrate the need for policy measures to reduce potential plastics emissions into natural ecosystems and mitigate ocean ecosystem impacts."