The world’s oceans contain an enormous variety of life in a wide range of habitats. The oceans cover 71 per cent of the surface area of the planet and constitute more than 90 per cent of its habitable space. They are home to the largest animals ever to have lived on Earth and billions upon billions of the tiniest.

The top 100 metres of the open oceans host the great majority of the sea life with which we are most familiar—turtles, fish and marine mammals—as well as the microscopic plankton that form an integral part of the marine food web and provide so much of the oxygen that we breathe. Far below the surface, in the dark depths, seamounts—underwater mountains that rise 1,000 metres or more from the seafloor—provide habitat for rich and diverse communities.

From sandy shores to the darkest depths of the sea, the oceans and coasts support a rich tapestry of life: shorebirds that stalk across mudflats in search of shellfish prey; alligators that ease their way through mangrove swamps; kelp forests that sway beneath the waves; polar bears that stalk seals across the Arctic sea ice; penguins trying to evade seals in the Southern Ocean of Antarctica; and tiny photosynthesizing plants called “phytoplankton” that provide 50 per cent of all the oxygen on Earth.