Scientists have discovered that subtle changes in seawater colour can help them monitor the critically important Antarctic krill from space.

These tiny marine creatures, just a couple of inches long, are among the most abundant and vital animals on Earth, serving as a key food source for whales, penguins, seals, and seabirds.

Conservationists worry that krill populations may be declining due to climate change and fishing, highlighting the need for innovative monitoring methods.

“Antarctic krill are the superheroes of the Southern Ocean,” said Rod Downie, chief polar adviser at the wildlife charity WWF-UK.

“They are tiny, unsung heroes that sustain incredible marine life, but climate change and unsustainable fishing are putting them at risk.”

Researchers from the University of Strathclyde, WWF, and the British Antarctic Survey (BAS) are developing a satellite-based system to estimate krill numbers in the Southern Ocean.

The technique relies on analysing how seawater absorbs light, which varies depending on krill density.

Dr. Cait McCarry, from the University of Strathclyde, recently returned from Antarctica, where she collected krill to measure their effect on ocean colour.

“We start with seawater, then we add in a krill and take a measurement [of how much light the water absorbs],” she explained. “Then we add another krill and take another measurement.”

By understanding these subtle changes, scientists aim to use satellites to create snapshots of krill populations from space.

Krill play a crucial role in the marine ecosystem, supporting some of the planet’s largest animals, including migratory whales that travel thousands of kilometres to feed on them. These tiny creatures also contribute to a healthy ocean cycle: whales consume krill, krill feed on microscopic plants living in sea ice, and these plants absorb carbon dioxide as they grow. Whale faeces, rich in nutrients, then fertilise these carbon-absorbing plants, helping regulate the climate.

However, rising ocean temperatures caused by climate change threaten to disrupt this delicate balance, potentially making krill populations vulnerable.

Scientists hope that by monitoring krill from space, they can better understand these threats and work towards conservation solutions.

Mr Downie said: “We urgently need to better manage the fishery and protect krill habitats within a network of marine protected areas.

“[This project could] give us a new tool to help monitor and safeguard this vital species.”