Researchers in the US may have found a new aid in the climate change battle – and it involves some of the world's smallest animals and their tiny poops.

A study led by Dartmouth College, Hanover, New Hampshire, has recruited trillions of microscopic sea creatures called zooplankton to remove carbon from the atmosphere.

Scientists from the college report that spraying clay dust on the surface of the ocean converts carbon into food the animals would eat, digest and send deep into the ocean as carbon-filled faeces.

This technique harnesses the animals’ ravenous appetites to accelerate the ocean’s natural carbon-removal cycle, which is known as the biological pump, according to the paper in Nature Scientific Reports.

The process begins with spraying the clay dust at the end of algae blooms. These blooms can grow to cover hundreds of square kilometres and remove about 150 billion tons of carbon dioxide from the atmosphere each year, converting it into organic carbon particulates.

Once the bloom dies, marine bacteria devour the particulates, releasing most of the captured carbon back into the atmosphere.

The study found the clay dust attaches to carbon particulates before they re-enter the atmosphere, redirecting them into the marine food chain as tiny sticky pellets the ravenous zooplankton consume and later excrete at lower depths.

“Normally, only a small fraction of the carbon captured at the surface makes it into the deep ocean for long-term storage,” says Mukul Sharma, professor of earth sciences.

“The novelty of our method is using clay to make the biological pump more efficient - the zooplankton generate clay-laden poops that sink faster.

“This particulate material is what these little guys are designed to eat. Our experiments showed they cannot tell if it’s clay and phytoplankton or only phytoplankton - they just eat it,” he says.

“And when they poop it out, they are hundreds of metres below the surface and all that carbon is, too.”

The team conducted laboratory experiments on water collected from the Gulf of Maine during a 2023 algae bloom. They found that when clay attaches to the organic carbon released when a bloom dies, it prompts marine bacteria to produce a kind of glue that causes the clay and organic carbon to form little balls called flocs.

The flocs become part of the daily smorgasbord of particulates that zooplankton gorge on, the researchers report. Once digested, the flocs embedded in the animals’ faeces sinks, potentially burying the carbon at depths where it can be stored for millennia.

In the ocean, the flocs become an essential part of the biological pump called marine snow, Sharma says. Marine snow is the constant shower of corpses, minerals, and other organic matter that falls from the surface, bringing food and nutrients to the deeper ocean.

“We’re creating marine snow that can bury carbon at a much greater speed by specifically attaching to a mixture of clay minerals,” Sharma says.

Under cover of darkness, the zooplankton —each measuring about three-hundredths of an inch—rise hundreds, and even thousands, of feet from the deep in one immense motion to feed in the nutrient-rich water near the surface. The scale is akin to an entire town walking hundreds of miles every night to their favorite restaurant.

When day breaks, the animals return to deeper water, where they deposit the flocs as faeces. This process is another key aspect of the ocean’s biological pump that shaves days off the time it takes carbon to reach lower depths by sinking.

Sharma plans to field-test the method by spraying clay on phytoplankton blooms off the coast of Southern California using a crop-dusting airplane. He hopes that sensors placed at various depths offshore will capture how different species of zooplankton consume the clay-carbon flocs so that the research team can better gauge the optimal timing and locations to deploy this method and exactly how much carbon it’s confining to the deep.

“It is very important to find the right oceanographic setting to do this work. You cannot go around willy-nilly dumping clay everywhere,” Sharma says.

“We need to understand the efficiency first at different depths so we can understand the best places to initiate this process before we put it to work. We are not there yet - we are at the beginning.”