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There is 10,000 times more plastic in the deep sea than in surface waters.

Locations of sampling sites of bottom sediment and deep-water coral where content of microplastics was investigated.

Locations of sampling sites of bottom sediment and deep-water coral where content of microplastics was investigated. From Woodall et al. 2014.

Ocean plastics is one of the most pernicious problems facing the ocean. One-time use plastics, which, ironically, can persist for thousands of years, often find themselves carried downstream, settling on our beaches, our coastlines, and in large aggregations within oceanic gyres. We’re still trying to cope with the extent to which plastics, and particularly microplastics–tiny photodegraded plastic particles, impact marine ecosystems. Earlier this year, ocean plastics made major waves when it was reported that not only do we not know how much damage they really cause, but we don’t even know where most of them go: 99% of the plastic that should be in the ocean is missing.

It looks like we found the missing plastic.

A new paper, published today, finally sheds some light on the fate of missing plastics. In “The deep sea is a major sink for microplastic debris” Woodall and friends reveal that there are four orders of magnitude–that’s 10,000 times–more microplastics in deep-sea sediments than in surface waters. They surveyed deep-sea sediments from around the world, in the Indian and Atlantic Oceans, as well as the Mediterranean Sea, and discovered that fibrous microplastics, particularly rayon and polyester, were ubiquitous in all sediment samples.

Let that sink in. 

Human-generated microplastics are not just abundant in the deep sea, but they are a global component of all deep-sea sediments. In my own expeditions, I’ve seen garbage littering the seafloor at even the deepest and most remote locations, but it was also in discrete patches and low abundance. This new study suggests that plastic pollution has impacted all deep-sea ecosystems in tremendous quantities. Microplastic fibers were also found covering delicate deep-sea octocorals–not at some sites, but at every site.

They estimate that there are four billion fibers per square kilometer in Indian Ocean sediments. It is clear that the deep sea has become a sink for our plastic waste.

Sadly, this study only looks at presence and abundance, but it is an important first step in understanding how human garbage impact the deep sea. We have no idea what, if any, effect these microplastics have on deep benthic communities–heck, we barely understand what microplastics do to surface ocean communities. That 99% of all ocean plastic could be hidden in the deep sea, even as public awareness of plastic pollution continues to rise points to on critical solution.

The only way to fix the plastic problem is to prevent plastic from reaching the ocean in the first place.

The paper, The deep sea is a major sink for microplastic debris, is short, excellently written, and open-access. I encourage everyone to read it.

Marine science and conservation. Deep-sea ecology. Population genetics. Underwater robots. Open-source instrumentation. The deep sea is Earth's last great wilderness.

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