How much plastic is in the ocean?

Researchers estimate there's 10 x more plastic in the Atlantic Ocean than previously thought.....
25 August 2020

Interview with 

Katsia Pabortsava, National Oceanographic Centre

PLASTIC_OCEAN

a photo of a plastic cup in the surf

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According to a recent survey, the rise in home deliveries over lockdown has led to a 30% increase in the amount of plastic we’re throwing away. Of course, some plastic items are essential for fighting Covid-19, but the more plastic we use, the more that also ends up in the ocean where it breaks up into tiny particles called microplastics. These can concentrate toxins from the water and carry them up the food chain, potentially back into us. And while we knew this was a problem, we thought we understood the scale of it. That is, until now; because a team from the UK’s National Oceanographic Centre have discovered plastic levels in the Atlantic Ocean are considerably greater than we previously thought, as Phil Sansom heard from Katsia Pabortsava…

Katsia - We find at least 10 times more plastic contaminants in the ocean that we previously thought.

Phil - 10 times? That's quite alarming, isn't it?

Katsia - At least 10 times. So it should be more alarming. The fact that there are many of them and in this sort of quantities, it doesn't sound promising.

Phil - How big are the microplastics you're looking at, and what plastics exactly?

Katsia - We're looking at the microplastic particles, which are larger than 25 microns. So if a human hair is about 70 microns, you can do the math. It's nearly three times less. And we look at three most common plastic types, polyethylene, polypropylene, and polystyrene. So these are also the most littered.

Phil - Were you expecting there to be such a huge underestimate?

Katsia - Well, in the past few years, scientists were trying to solve the mystery of the missing plastic. We know how much we approximately supplied into the ocean in the past 65 years, but what we have been measuring in the surface ocean so far was just about 1% of that. But what we find in just the top 300 metres of the Atlantic Ocean, and just with three polymers of very limited size range, we find the quantities which are comparable to the amount that we have put in so far. So that is the striking finding of this study.

Phil - How did you go about then getting measurements from under the surface?

Katsia - We've got this wonderful opportunity to join a research ship that sails every year from the UK down to the Falklands, across the middle of the Atlantic. Every day we stop, and then we lower our instrumentation down into the ocean. They collect water samples or particles.

Phil - What's your instrument?

Katsia - Essentially, it is a pump loaded with a very fine filter. So what you end up having is all sorts of particles, including microplastics.

Phil - Is this the first time that anyone had done this? Gone out right to the middle of the ocean and lowered a filter on a line to get these measurements?

Katsia - For microplastic measurement specifically, yes. We were the first who has done it. The previous studies were measuring plastic, only in the very top layer of the ocean. And those studies were looking at larger plastic bits.

Phil - And we have all these qualifications, like, you know, you only measured above a certain size. You only looked at a few different kinds. You only looked at this area of the ocean, but given that you found this underestimate of 10 times, is that something that in theory might exist for other sizes, all sizes, all kinds of plastic. We just don't know it yet?

Katsia - Oh yes, absolutely. Yes. Previously we looked at fairly big plastic particles, and we found them in those concentrations. And then we also saw that those types of plastics are eaten by sea birds, or whales, or other organisms. Now we're talking very, very small plastic particles, and they can be eaten by much smaller organisms, and which then are eaten up by bigger organisms. So if they contain some sort of toxic or dangerous compounds in them, that would propagate up the food chain. And ultimately if a fish eats a lot of those particles, then we eat fish, the effects might be even reaching us. And that's why it is very, very important to tackle the question of exposure for all plastics, everywhere in the ocean. Because what our research looked at is just three polymers. It's a limited size range, and it's a small part of the ocean. And we already find so much.

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