Ocean Plastics May Be Even More Persistent Than Was Previously Thought

After devoting my time into writing some articles regarding more broad aspects of the impacts of human activity to the environment. I would like to go back to my first subject, which is ocean plastic litter.

It’s not new to anyone (or it shouldn’t be) that the mass consumption of short-lived plastic products coupled with bad residue management and little strict international policies regarding trash exports resulted in huge leaks of these toxic pollutants into the environment. So much so, that these materials are everywhere and adding to the pressures suffered by ecosystems in this troubled 21st century.

Even knowing how bad the situation is, according to the estimated inputs of plastic litter to the ocean, it should be really worse. We should be seeing millions of tons of plastics floating at sea. But we aren’t. There is an estimate of only several hundred thousand tons of plastic litter there (an astounding figure anyways).

It was estimated that if plastic inputs into the ocean where stopped, the ocean surface would be free of plastic in only a few years, because of degradation and sedimentation.

Until very recently, plastic litter was thought to degrade into smaller fragments and precipitate, accumulating on the sea-bed. It was called the smog-hypothesis, because just like a smog descents the atmosphere to accumulate in the ground, microplastics supposedly formed a similar smog that descents to the ocean flor.

Well, this hypothesis seems to be coherent with previous findings.

Although it is very difficult to determine the age of plastic litter, and actually, there is no method to accurately determine this. There are some clues, such as labels, date of fabrication and organisms growing on debris that indicate for how long they were floating before collection.

And in fact, plastic products dating back to production in the 70’s and 80’s are commonly collected at sea. Which indicates that these polymers can stay there longer than previously thought.

But it conflicts with the smog hypothesis.

In order to take into account both the significant occurrence of decades-old plastic litter and the large difference between mass inputs and mass accumulation, researchers at The Ocean Cleanup came up with a new hypothesis.

In their recent report published at Scientific Reports, they argue that coastal environments play a major role in capturing and filtering ocean plastic debris. According to the report, plastic products that enter the ocean from coastal inputs are likely to get beached. Tides and waves may retrieve them, but they end up beached again. These cycles can be repeated several times before debris actually escape off-shore, significantly delaying accumulation in ocean gyres.

According to the authors:

Taking these insights into account, they modelled ocean plastic accumulation for three different scenarios: 1)Business as usual, where river inputs grow with plastic products demand, 2)Significant mitigation efforts implemented, by levelling sources to a constant value starting in 2020, 3)Drastic efforts are taken to cut sources down completely by 2020.

It is a key change in our understanding of plastic pollution, since it suggests that plastic debris won’t simply sink to the bottom of the ocean and disappear, rather, even if inputs were stopped, microplastic pollution would still increase for several decades. In fact, by mid-century, it is expected to more than double, as material left in the environment is slowly fragmenting.

For the team at The Ocean Cleanup, these results point clearly that mitigation efforts should focus not only in prevention, but as well as in curative technologies.

They are currently testing a prototype to remove floating debris from the ocean surface, idealised by the founder of the organization, Boyan Slat and designed by it’s collaborators.

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