Plastic in the sea

Plastic pollution can be described in three words:  omnipresence, irreversibility and multifaceted impacts.

Among the multiple changes that human activities have on marine environment, plastic litter in the sea is taking over the protagonist role due to its constant increase over the time (annual increase of 9% in the global consumption of plastic). Despite the fact that around 60% of plastic debris sank and accumulate on the seabed, the pollution of superficial water raise a lot of concern considering its impact on the living biota.

60% of plastic debris accumulate on the seabed limiting the gas exchange between the seabed surface and the water column leading to anoxic conditions and threatening the benthic communities.

40% of the plastic debris float in the superficial water and is present in the form of small fragments: microplastics.
Photo credit: Arnaud Conne

Plankton, at the base of the food chain, interacts with microplastics.

Ocean currents transport marine debris creating accumulation zone improperly called “plastic continents”.

It is estimated that 8 million tons of plastic waste is annually discharged in the oceans. This waste breaks up into particles whose dimensions range from the millimeter to the micrometer, the same as that of the plankton. Once they reach this state they are ingested and absorbed by organisms that confuse them with plankton and poison themselves or choke on them.

In conclusion, some of the main consequences of plastic pollution are:

  • The environment: plastic debris accumulate on the seabed (limiting the gaseous exchange between the sediments and the water), cause the death of marine fauna by asphyxiation, choking or by accumulation of plastic in the stomach. Plastic fragments act like floating platform on which invasive species can hitch a ride. Microplastics can interact with hydrophobic pollutants such as POPs which concentrating at the surface of plastic particles can reach several orders of magnitude higher than that in sea water. Microplastics and the pollutants carried on their surface can be ingested by aquatic organisms and transported up into the food chain.
  • Human activities: marine debris is a danger to navigation and safety at sea, it affects tourism, land beaches and makes work more difficult for fishermen.
  • Human health: consequences on human health by the effect of food chain is now a concern.

The ocean pollution by plastic waste and waste patches formation is increasingly mediated. Nevertheless, this issue remains extremely mysterious. We still ignore what happen to the majority of marine debris.