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Phytoplankton, El Niño, and Global Warming

How does such a tiny organism do so much to help reduce global warming?

a view of the Pacific Ocean from space

Photo: blueforce4116 (flickr)

The Earth's oceans absorb carbon dioxide, a major greenhouse gas, from the atmosphere.

Global warming, as you know, is a huge problem, and is in some ways more complicated than we sometimes think. Much of the problem is our fault, as a failure to check greenhouse gas emissions has increasingly turned our atmosphere into a heat trap. However, there are natural forces at play, too, both helpful and harmful.

For example, you may have heard that the oceans absorb carbon dioxide, a major greenhouse gas, from the atmosphere. That’s true, but it’s not the water in the oceans so much as the plants and animals that live there. Tiny, single-celled creatures called phytoplankton, for instance, live near the ocean’s surface and use lots of dissolved carbon dioxide for photosynthesis. When phytoplankton die and sink to the ocean floor, most of the CO2 they consume returns to the atmosphere, but enough CO2 sinks down with the phytoplankton to balance out CO2 levels in the atmosphere and help reduce global warming.

To be clear, this isn’t to say that we can rely on phytoplankton to solve our global warming problems. Phytoplankton are vulnerable to weather and other changes that affect their health.

For example, when El Niño sweeps through every three to six years or so, it causes fewer nutrients to be swept up from the ocean floor to the surface where phytoplankton feed. Fewer nutrients means fewer phytoplankton. Fewer phytoplankton means less CO2 absorbed from the atmosphere, which makes global warming an even bigger problem. Stopping or reversing the effects of global warming will require a giant effort, but it depends in part on paying attention to some very small things, like phytoplankton.

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