PLASTIC: You are plankton and to plankton you shall return

Today, I’m going to talk about public enemy number 1, plastic; and more specifically, I’ll tell you about their interaction with marine plankton.

Plastic, from the Greek plastikos: which can be shaped, is a word that includes a multitude of products of different origin and chemical composition. Some are more or less natural, but most are purely artificial. What you may not know is that many plastics are made from petroleum products, which originated from plankton millions of years ago.

Imagine copepods were made up of plastic ;–)

Is plastic as bad as they want us to believe?

Well, honestly, plastic isn’t to blame for who it is at all. In fact, it’s one of the most revolutionary inventions of the last few centuries, along with Sunday afternoon movies and popcorn. What is bad is the abusive and irrational use we make of it. Most plastics are made to last, and we give them a single-use. And the worst thing is that most times, once used, they end up where so many things end up, the sea. There, plastics begin a process of degradation, usually quite slow, depending on their chemical composition and environmental conditions. For example, a plastic bottle can take about 500 years to degrade completely. However, from around 1860, when the first plastic was produced (a billiard ball, by the way) until today, many of the containers and plastic materials that have ended up in the sea have decomposed into small particles (microplastics) of a few microns (thousandths of a millimeter) that are now suspended in the water column in greater or lesser concentration or have ended up in the sediments. Moreover, our daily life generates a lot of plastic fibers and microparticles. For example, in every wash of a washing machine, which you do on Sundays if you are single or almost every day if you have children, more than 700,000 particles are released, most of which will surely end up in the sea. I should say here that water treatment plants cannot cope efficiently with microplastics. Just in case you still need more examples: many cosmetics still carry microplastics in their formula, microscopic fragments of tires that come off when you circulate with your car, by-products of industrial activity, etc., are also other of the multiple origins of marine microplastics.

Why are microplastics important?

The most serious problem with microplastics is that they end up entering the marine food web, either though plankton or through fish, among other organisms. This is because these particles are within the size range of plankton or fish prey. For example, 60% of the sardines and anchovies we consume in Catalonia (NW Mediterranean) have a piece of plastic incorporated into their digestive tract. But don’t suffer. We probably ingest more plastic every time we get into our brand-new car (mostly made of plastic in its interior) than eating 1 Kg of sardines. In fact, we ingest about 5 grams of plastic a week from different origins, which is about the equivalent of a cookie (a plastic one; yummy!). The same thing that happens to sardines happens to zooplankton. They sometimes confuse microplastics with prey and ingest them. Laboratory experiments show that both copepods and protozoa consume plastics when they are in high concentrations. Fortunately, the present concentrations of these particles in the sea are still quite low, so the problem does not seem that serious. Yet, if we consider that every year about 8 million tons of plastic enter the sea (i.e. about 500 Eiffel Tower) we can think that in a not so distant future the concentration of microplastics in water can represent a real threat, even for plankton.

Are microplastics harmful?

Usually, the ingested plastic particles pass through the digestive tracts of the organisms and the thing does not go further than a certain degree of constipation. However, some products used to produce plastics (plasticizers and other additives) are toxic and certain plastics have an affinity for pollutant compounds (such as hydrocarbons) and accumulate them. Toxicity of microplastics is being studied in laboratory experiments, but a field approach, with much more precise analytical techniques than current ones, would be needed to properly assess whether we face a real hazard. 

In short, if you use plastic, reuse it and at the end of its useful life, recycle it properly. Together, we should try to ensure that our sea does not end up being a sea of ​​plastic.

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