Hidden Heroes of Climate Change: Zooplankton's Role in Carbon Sequestration

A study highlights the crucial role of zooplankton in carbon storage, equating their contributions to the annual emissions from 55 million petrol cars. However, rising threats from climate change and commercial fishing could jeopardize their effectiveness in combating global warming.

A relatively unknown creature often associated with aquarium food may hold the key to fighting global warming, according to groundbreaking research. Zooplankton, small marine animals that undergo dramatic migrations, have been discovered to sequester carbon by consuming phytoplankton and burning stored fat, preventing it from re-entering the atmosphere. Researchers estimate that these tiny heroes can store as much carbon as the emissions produced by approximately 55 million petrol cars.

Lead researcher Dr. Guang Yang from the Chinese Academy of Sciences calls the findings "remarkable," highlighting a re-examination of how such species contribute to climate stability. Despite their importance, zooplankton rarely receive the recognition afforded to larger Antarctic animals like whales and penguins.

Take copepods, for example, which range from 1-10mm in size. They primarily inhabit deep ocean waters, resting between 500m and 2km below the surface. These creatures sustain themselves on phytoplankton, converting it into fat, which acts as a carbon storage system. During their annual migration to deeper waters, these fats are gradually utilized, effectively locking away carbon dioxide.

"Their fat is like a battery pack," explains Professor Daniel Mayor from the University of Exeter. As zooplankton dive, the carbon-rich waste they produce contributes to the "seasonal vertical migration pump," which transports about 65 million tonnes of carbon to profound ocean depths each year — equivalent to the annual emissions of millions of diesel cars.

The research team unveiled this carbon storage mechanism through extensive data analysis dating back to the 1920s. The expedition aboard the Sir David Attenborough polar research ship involved meticulously collecting zooplankton specimens under controlled conditions. Despite their small size, researchers stress that the health of zooplankton is crucial to regulating the Earth's atmosphere.

However, the future of these vital organisms is under threat from climate change, commercial harvesting, and ocean disturbances. The United Nations reported that almost half a million tonnes of krill, a type of zooplankton, were harvested in 2020 alone, raising concerns about long-term sustainability. Researchers advocate for incorporating these insights into climate models to better understand potential atmospheric impacts.

"The biological pump of zooplankton transforms our understanding of carbon sequestration," notes co-author Professor Angus Atkinson. Without their efforts, atmospheric CO2 could potentially double, putting the planet at greater risk of warming.

This research, published in the journal Limnology and Oceanography, sheds light on the often overlooked contributions of zooplankton and emphasizes the urgent need to protect these marine "unsung heroes" in the face of looming environmental threats.