How do tiny marine microbes affect global carbon?

Carbon dioxide in the atmosphere traps the sun’s heat and helps warm the planet. Too much carbon dioxide drives global warming and climate change. But at the ocean’s surface, the gas moves between air and water. Once in the ocean, some of it can be locked away to help prevent more warming. Marine microbes play an important role in this process.

When sun shines on the ocean’s surface, tiny phytoplankton get to work. These microscopic, plant-like algae pull carbon dioxide from seawater. Then they use sunlight to turn it into food. That food feeds the ocean, forming the base of the marine food web. Small zooplankton snack on phytoplankton. And bigger organisms snack on them. As consumers process the food they eat, they release carbon dioxide back into the ocean.

But not all of that carbon stays near the surface. Over time, through messy eating and plenty of pooping, some of the carbon sinks through the ocean’s depths, falling as marine snow. Some of these fluffy leftovers are visible, but others are too small to see without a microscope. If they reach the deep ocean, the carbon they contain can be locked away for hundreds or even thousands of years. In this way, the ocean has slowed global warming by storing vast amounts of carbon, and scientists recently discovered part of the reason why: tiny marine microbes.

Although the open ocean looks empty, its waters teem with microscopic life. An assortment of single-celled organisms fills every teaspoon of water. A single liter of seawater contains millions of microbes. They’re everywhere, an invisible force that transforms carbon as it moves through the water column.