Tiny creatures gorge, get fat, and help fight global warming

Zooplankton, tiny animals living in the cold waters around Antarctica, are playing a surprising and important role in fighting global warming. These creatures, which are often sold as food for aquarium fish, have a unique way of helping the planet. According to new research, zooplankton eat a lot during the spring, storing up fat in their bodies. Then, they migrate deep into the ocean, sometimes hundreds or even thousands of meters below the surface, where they slowly burn off this fat. This process locks away a huge amount of carbon, which would otherwise stay in the atmosphere and make the planet warmer. Scientists have discovered that the amount of carbon stored by these animals is equal to the yearly emissions from about 55 million cars. This is much more than anyone expected.

The most important type of zooplankton in this process is the copepod, a tiny animal related to crabs and lobsters. Copepods are only about 1 to 10 millimeters long, but they have a big impact. They spend most of their lives deep in the ocean, sleeping and slowly using up the fat they stored during the spring. When they eat phytoplankton, which are tiny plants that live near the surface of the ocean, they turn the carbon from these plants into fat. Scientists have taken close-up pictures of copepods and can see the fat stored inside their bodies. Without these animals, the Earth's atmosphere would have much more carbon dioxide, making the planet even warmer. The oceans have already absorbed about 90 percent of the extra heat caused by humans burning fossil fuels, and the Southern Ocean near Antarctica is responsible for about 40 percent of that. Zooplankton are a big reason why this happens.

Researchers have spent years studying how zooplankton help store carbon in the ocean. They already knew that when zooplankton produce waste, it sinks to the bottom of the ocean, taking carbon with it. But the new research shows that the animals' yearly migration into the deep ocean is even more important. This process, called the seasonal vertical migration pump, moves about 65 million tonnes of carbon every year to at least 500 meters below the surface. Copepods are the main contributors, but other animals like krill and salps also help. This is equal to the pollution from 55 million diesel cars each year.

To learn more about zooplankton, scientists travel to Antarctica on special research ships. They use large nets to catch the animals and study them under microscopes. Sometimes, they have to work in complete darkness or in very cold rooms to keep the zooplankton safe. However, there are growing threats to these important creatures. The ocean is getting warmer, and commercial fishing for krill is increasing. In 2020, almost half a million tonnes of krill were caught. If the number of zooplankton goes down, less carbon will be stored in the ocean, and the planet could get warmer. Scientists say that their new findings should be included in climate models to better predict how much the Earth will warm in the future. Zooplankton may be small and easy to overlook, but they are doing a huge job to help protect our planet from climate change.