Oceans, which cover 70 percent of the Earth's surface and are essential to humankind, are in a critical state. While fish stocks have plummeted due to over-fishing, pollution — especially plastic debris — is also taking a toll on marine animals, which ingest it or get tangled up in it.

When they met in Japan in May, the Group of Seven environmental ministers acknowledged that a form of plastic debris known as microplastics constitutes a threat to marine ecosystems. The World Economic Forum estimates that the total weight of microplastics in the oceans will top that of fish by 2050.

It is also feared that an increased concentration of carbon dioxide in the atmosphere — though to be as a main source of global warming — will acidify the oceans as well as raise their temperature.