Though practically invisible, phytoplankton make up an overwhelming 98 percent of the biomass of ocean life and generate more than half the oxygen produced on the entire planet. The microscopic organisms are the base of the food chain, but their impact is significant. Unfortunately, plankton may not stick around much longer.

In the past several decades, global plankton populations have declined due to climate change. Because human life depends on the presence of these oxygen-producing creatures, marine biologist Chris Bowler is working to study plankton as much as possible before they disappear. Bowler and a team of other scientists have been collecting plankton samples across the world for the past 2 1/2 years as part of the Tara Oceans expedition.

The expedition was a massive effort along a 62,000 mile journey, visiting 32 countries with a total 196 people who took turns aboard (126 scientists, 24 journalists, 7 artists, 8 cooks, 23 sailors, 3 customs officials, 1 doctor, 4 guests). The expedition cost about 9 million euros.

An ideal study of climate change impact on plankton populations would involve monitoring the same location over a period of time, watching what happens to the various species of microorganisms as time passes. The Tara Oceans team, however, collected samples from around the world, and will use that data to determine which plankton are likely to migrate, thrive or go extinct as certain conditions arise in waters across the globe. The expedition has collected approximately 27,000 samples, which the team will study to determine which varieties of plankton prefer particular habitats (more polluted, more acidic, etc.) and have a better understanding of which species will be able to survive forecast conditions.

The team has discovered up to one million new species of microorganisms. It will take years to sift through all of the samples, by which point some species may already be extinct. Hopefully, however, the research will show a great enough population of plankton will be able to live in warm, acidic waters.

Main image: plankton mix from scientific station 146. Credit: C. Sardet/CNRS/Tara Oceans