Living Waters

A virus has caused us to scramble for oxygen but our chokehold on the environment is slowly strangling the very waters that breathe life into us. The virus is a timely reminder: We are merely consumers, not producers of life’s breath on this planet

- MADHU KAPPARATH

A MAGNIFIED VIEW OF PHYTOPLANKTON

Almost 70 percent of the oxygen we breathe comes from microscopic plant-like organisms called phytoplankton (or microalgae) that live on the surface of oceans and lakes. One type of phytoplankton, Prochlorococcus, produces up to 20 percent of the oxygen found in our entire biosphere. It is so small that millions can fit in a drop of water. These drifting marine organisms photosynthesize, using carbon dioxide, water, and energy from the sun, releasing tonnes of oxygen, a process they’ve been at for billions of years.

A FISHEYE VIEW OF THE GREAT BARRIER REEF MARINE PARK, AUSTRALIA

The earliest known photosynthesising marine fossil we have a record of goes back 3.5 billion years. The ocean was producing oxygen for billions of years before that. Early in our planet’s history, the atmosphere had almost no oxygen. Oxygen generated as a byproduct by photosynthesizing microbes eventually built up in the atmosphere, drastically changing our planet’s environment and the history of life in the process.

A kelp forest flanks a sea lion in the Pacific Ocean off San Benito Island, Mexico