Oceans of plastic

© The Petri dish is placed on a luminscent layer in order to sort out the micro plastic fragments.

For over half a century, plastics have invaded our daily lives, but also our oceans, representing the vast majority of marine pollution. The world of silence, so dear to Cousteau, is gradually becoming the world of plastic …

For industrialists, plastic is a blessing. Low cost of production, but also ideal properties: strong, lightweight, resistant to corrosion and many chemicals, etc. By adding various additives, flame retardant, for example, the possibilities are almost endless. No wonder that the production of plastics has ceased to increase in recent decades, apart from a brief decline in the late 2000s. Beginning with a very small production in the middle of the 20th century, the industry currently produces about 300 million tons of plastic each year, used in almost all sectors, including construction, electronics, automotive industry, and most importantly, throw-away packaging – representing nearly half of all plastics produced. 


Packaging used only once may impact the environment for a very long time

With its formidable properties of resistance, plastic is made to last – dozens, sometimes hundreds of years. When plastic is not subject to thorough sorting and recycling (today only 20% of plastic in France is recycled), it inevitably ends up in nature, and especially in the sea. Each year, between 10 and 20 million tons of waste of all kinds are dumped into the oceans, of which a large majority are plastics. On the surface, nearly all of the floating objects are plastic. While some trash comes from maritime activities, an average of 70 to 80% of marine debris originates on land, conveyed by rivers and streams.


Once at sea, most of the plastic waste floats on the surface

Carried over huge distances by ocean currents, they float into the most remote areas of the planet. Some get stranded on the coast, but others are caught in ocean gyres – huge eddies covering several thousand kilometers. One of these gyres – located in the North Pacific – was brought to light in 1990 by the oceanographer Charles Moore, who called it “the continent of plastic.” The term is strong, but hardly describes the reality. Far from being an island of garbage emerging from the ocean, it is rather a high concentration of floating debris. Some are large-sized pieces of trash, called “macroplastics” – water bottles, plastic bags and other packaging. But there are also small particles measuring less than 5 millimeters called “microplastics.” These gyres form a veritable soup of tiny plastic debris resulting from the slow breakdown of macroplastics.

Microplastics are not only confined to oceanic gyres, but are found everywhere on the planet. The Mediterranean, a nearly-closed sea, suffers from the highest density of microplastic in the world: 115,000 particles per square kilometer. For a long time the subject was ignored by the scientific community, and it’s only recently that studies of this form of plastic (much less visible than large floating objects) have finally begun. The magnitude, distribution and especially the potential impact of this phenomenon on the environment are therefore still unknown. Much remains to be done, and Tara hopes to make a contribution to this research, taking advantage of the 7-month Mediterranean expedition to gather a maximum amount of information about microplastics and their interactions with the planktonic ecosystem.



Yann Chavance



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