The ocean covers about 71 percent of Earth and holds an enormous variety of life, much of it still undescribed.

Habitats

Coral reefs occupy a tiny fraction of the sea floor yet shelter around a quarter of known marine species. The deep sea, in contrast, is the largest habitat on the planet.

Food webs

Microscopic phytoplankton form the base of most marine food chains and produce a large share of the oxygen we breathe. Predators such as penguins depend on these chains.

Pressures

Warming water, acidification, plastic pollution and overfishing are changing marine ecosystems quickly.