Pollution and microplastics: the sea is in jeopardy!

Without a doubt, the sea is in jeopardy. Largely because of plastic waste and microplastics. But not only that. Other sources of pollution add up together, combine and increase the irreparable damage to marine flora and fauna. 

What kinds of pollution have given rise to this ecological catastrophe? What can we do to save the sea and keep the planet cleaner?

Who is polluting the sea?

Everything, or almost everything, that gets discharged into the sea is harmful. Apart from organic waste like apple peel, the marine ecosystem is not designed to receive toxic or plastic material. The sea’s remarkable ability to repair and renew itself allows it to withstand pollution… Up to a certain point. The pollution is now too great, too diverse and too relentless for the sea to absorb.

The same applies to the plastic that accumulates in the sea. A distinction is generally made between waste and litter dropped by people (or carried by the wind), like plastic bottles, and chemical substances. These are carried in with wastewater in some parts of the world where sewers and water treatment plants are lacking (laundry detergent and shampoo end up in the sea).

In our part of the world, the design of rainwater gutter networks means that a cigarette butt thrown into a gutter in the city, or bleach used to clean a porch and rinsed away in the street, ends up in the sea… Beyond the ecological aspect, the contamination of seawater with wastewater poses a worrying public health problem for bathers. Bacteria in polluted seawater do cause diseases (skin complaints, respiratory complaints, diarrhoea) that reach millions of cases annually.

Contaminating industrial waste

Of course, the sea suffers due to all the waste that ends up in it. This is the case whether it be toxic wastewater, or various polluting substances like industrial waste or construction debris. This is made up of paint, solvents or unused concrete, or materials containing heavy metals and lots of plastics. These plastics often come from coverings and coatings that are impossible to remove from the sea: varnish, plastic films, plastic waste that has partially broken down… They may circulate via wastewater, but can also be carried by the wind if stored in the open. The wind and rain can make short work carrying plastic dust into a waterway.

What are dead zones?


 Chemical substances discharged via wastewater, by factories or carried by the rain from farms that use pesticides destroy any life form in the zone where they are shed. Land-based or aquatic flora dies in situ, as do “fixed” organisms: coral that cannot move, or some marine animals that are too slow-moving to switch habitats. When water does not get renewed quickly enough, this phenomenon gives rise to what are known as dead zones or “hypoxic” zones, whose low oxygen level brings about the irreversible destruction of ecosystems. There are hundreds of them of various sizes, which can reach a surface area equal to that of the UK! The first dead zones were pinpointed in the 1970s in the USA and the Black Sea, Adriatic and Baltic Seas in particular, where only primitive bacteria can survive. In the Gulf of Mexico, the substances discharged into the Mississippi have eradicated all fluvial wildlife across some 25,000 km and the area now constitutes the world’s largest dead zone

Oil slicks – a chronic ecological catastrophe

In the same vein, oil slicks are ecological catastrophes that some of those responsible try to downplay, whereas they annihilate sea life. Most often, these “catastrophes” result from human negligence, which itself arises out of cutting financial corners on the securing of shipping routes. Beyond incidents on oil rigs which can lead to oil leaking into the sea, oil slicks are caused by ageing ships (like the famous Liberia and Panama). These ships, which should no longer be permitted to transport hydrocarbons, play on the differences in legislation between countries to keep operating in our seas. On top of the risk of oil slicks, some discharge the oil from the bottoms of their tanks at sea totally illegally to avoid maintenance duty. Given that the consequences of an oil slick can last for years, it can be said that the sea is “chronically” polluted by hydrocarbons.

What about cigarette butts and small items of plastic litter?

At our level, each minor polluting habit repeated by millions of individuals becomes a sizeable problem, especially where plastic is involved. You may immediately think of cigarette butts squashed into the sand (yes indeed, even now it still happens). And also of bottle tops, lollypop sticks and other packaging items that holidaymakers leave behind. Because of its toxic substances (arsenic, lead, tar…), a single cigarette butt can pollute 500 litres of water. Its filter, made from cellulose acetate (a plastic fibre), takes more than 15 years to break down. Which leaves ample time for it to be swallowed by turtles. We have the ability to recycle and process cigarette butts, but first they need picking up. This costs money, and recycling schemes must be forecast as profitable before they can be implemented. In some countries like the UK, these schemes are financed by industrial tobacco groups. In France, collective and personal initiatives take care of picking up cigarette butts and small items of plastic litter from beaches. Because once they hit the sea, that is where they stay for evermore

Shampoo and sunscreen under scrutiny

When we go bathing, we leave a trail of… sunscreen! It’s invisible, and gets spread around through the water every time we go bathing. So what’s the problem? Whatever filters it contains, they harm marine fauna and flora. In particular, chemical (so-called organic) solar filters “bleach” (kill) coral and all the organisms that live in symbiosis with it. Water-soluble filters get dispersed in the water and ingested by marine animals. Lastly, natural (so-called mineral) filters in organic formulations, made from zinc dioxide or titanium dioxide powder, spread and settle on the sea bed and its marine life. These so-called biodegradable formulations are thought to be “least worst”, but it is too early to say so with any certainty. As for packaging, countless caps and cream tubes end up buried under the sand by the end of the day. Then there is silicon from haircare formulations, which behaves like plastic and is shed into water during rinsing without necessarily being able to be filtered out. These invisible substances, too, harm marine life (flora and fauna) and throw off the balance between their interactions.

Plastic in the sea – a floating monster  

 The four items that end up most often as polluting flotsam and jetsam are made from plastic:

  1. Cigarette butts
  2. Packaging items
  3. Plastic bottles
  4. Plastic bags

They are followed by polystyrene with its little white beads (that animals mistake for food), plastic cutlery, sanitary towels, nappies and cotton buds. Plastic waste is the number one marine pollution problem.

Indestructible composition

Plastic is a petrochemical oil concentrate, full of “polymers”, chemical molecules, additives and “adjuvants” that impart various features to it (colour, shape, flexibility…). It’s polluting across the board, throughout its life cycle. Starting with its production, which requires a great many constituents that are extremely harmful for the planet. The pollution continues through its use, whereby these substances (like endocrine disruptors such as bisphenol A) can be spread around or contaminate the human body. Up until its demise, which is in name only since… Plastic never goes away! It gets converted, recycled, dispersed into ever smaller fragments, until it turns into invisible microplastic, but it’s still there.

Breakdown into microplastic fragments

The positive qualities of plastic come at a price: it is strong enough to be durable, but not strong enough to not break down. Unfortunately, it is very often used to make items that are not built to last, or even for single use items. It takes longer to produce them than use them. And this plastic never assimilates into the natural environment, unlike other materials that can enter biogeochemical cycles. Metal and stone can be returned to the earth. Paper, cardboard, cotton and leather are assimilated by soil microorganisms. As for plastic, it just breaks down into ever smaller fragments to end its life as tiny specks that get into everything. In the sea, plastic waste and other items get eroded by salt, ultraviolet rays, the heat of the sun and waves. They turn into tiny plastic crumbs, invisible to the naked eye, and invade marine ecosystems. All these fragments of hard plastic, packaging items and synthetic fabric fibres turn the sea into a real plastic soup in some areas. Some spread and cover the sea bed and its plants, and others float and obstruct exchanges with the surface of the water. Unfortunately, fish mistake most of them for food.

How did plastic continents come about?

Microplastics are carried wherever the strong currents take them, and gather in “gyres”, vast areas of plastic soup, real floating monsters, and form expanses known as “plastic continents” or the “7th continent”. The plastic in the first gyre to be discovered (in the Pacific Ocean in 1997) is six times denser than its plankton. There are currently five major plastic continents, in the north Pacific, south Atlantic and Indian Ocean, and also smaller ones closer to home (in our case, France). The Mediterranean Sea is almost completely enclosed by land, meaning that plastic waste gathers in it and puts its incredible biodiversity in jeopardy. This includes marine mammals living in it like the dolphin, common fin whale and sperm whale. This phenomenon is particularly alarming in the Pelagos Sanctuary, a sea reserve spanning 87,500 m2 in the Corso-Liguro-Provençal basin, classed as a “specially protected area of Mediterranean significance” (ASPIM).  Because plastic does not stop at sea borders. This invasion can only be stopped upstream, by changing our habits and encouraging the authorities to implement robust, specific ecological policies. 

Microplastics – a risk to human health too

Beyond the ecological catastrophe caused by microplastics in the sea, there are public health risks attached for us humans. Marine organisms consume these plastic fragments inadvertently. If we then consume the affected shellfish and fish, it’s our turn to ingest them. A WWF survey reveals that we ingest some 5 grams of plastic per week in this way. That’s a credit card’s worth! Plastic is also ingested via bottled water and plastic crumbs that we might swallow after cutting up food in a plastic tray, a plate made from melamine (a plastic resin material that’s heavy and unbreakable) or on a plastic chopping board.

To get back to the subject of the sea, the most worrying thing currently is the phenomenon of the “plastisphere”. Plastic attracts organisms and bacteria which gear themselves around a new ecosystem. Some of them are pathogenic to living organisms, like the vibrio (a bacillus of which one particular species causes cholera), which can support toxic algae. Lastly, plastic can get loaded with pollutants that it transfers to our plates and our running water, and that it takes to the Arctic and the deepest ocean trenches, and even into the placentas of marine animals. 

The sea is polluted and marine ecosystems suffer and sometimes disappear, all over the world. To save them, we have to call production systems into question and have them work in a different way. Each of us can take action by breaking certain habits and embracing new ones as consumers, to apply pressure to decisionmakers and industrial groups.

It’s an emergency, because even if we were to halt consumption and therefore halt the shedding of plastic into the sea today, it would not stop the development of plastic continents overnight.

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