PLASTIC IN THE OCEAN

Ignoring or even denying the economic reality of the current ecological emergency would be to shut one's eyes to the close dependence of human activities on a stable and favourable environment

- Romain Troublé

The problem of maritime plastic-waste pollution first became apparent in the 1970s.

In the half-century since then, the problem has become ever more widespread, as scientific expeditions conducted by the Tara Ocean Foundation (of which I am executive director) have shown.

Large pieces of debris, such as fishing nets, and their disastrous effects on marine life, are the most visible symptom, Such waste is estimated to kill more than one million seabirds and over 100,000 marine mammals annually, often through entanglement or suffocation, and promotes transport of invasive species, triggering a cascading effect on the ecosystems in which they play a central role.

Less visible, but more pervasive, are microplastics, which have been found in the deepest ocean trenches and all types of marine life. Microplastics can, among other things, modify bacterial and viral communities and disperse chemical toxins in food chains. Some of these toxins, such as phthalates, are associated with the chemistry of plastics, while others, such as pesticides and heavy metals, are absorbed by the plastic before it reaches the ocean and enters the food chain.

How these toxic substances interact with plastics has been the subject of much study. Plastic is comprised of monomers that have been chemically bonded to form long chains of polymers - ethylene, styrene, and propylene become polyethylene, polystyrene, and polypropylene. But the process of polymerization is often imperfect, and some of the unpolymerized monomers that remain in plastic, like different types of styrene and bisphenol, pose major environmental and health risks.