A recent study has revealed that penguin guano in the water can significantly alter the swimming and feeding behaviour of Antarctic krill, a keystone species in the Southern Ocean. 

The research, published in Frontiers in Marine Science, shows how the presence of chemical cues in penguin guano can trigger an escape response in krill, potentially affecting the Antarctic food chain.

Krill’s reaction to penguin guano

In late 2022, scientists from Bigelow Laboratory for Ocean Sciences studied the impact of Adélie penguin guano on krill behaviour. In controlled experiments at Palmer Station’s research aquarium, the krill were placed in a flume filled with seawater. They were exposed to seawater contained algae, seawater containing penguin guano or seawater containing both. Notable differences in the krill’s swimming patterns were observed in the different scenarios. 

In controlled experiments at Palmer Station in Antarctica, they exposed krill to seawater containing penguin guano and observed notable changes in their swimming patterns.

Typically, krill swim steadily upstream, a behaviour known as rheotaxis. However, if there is poo in the water, they varied their swimming speed more, swam 1.2 to 1.5 times faster, and made three times more directional changes, suggesting attempts to evade predators. 

In another set of experiments, their feeding rate dropped by 64 percent due to the presence of penguin guano, indicating that their foraging efficiency was affected.

Why does this matter?

Krill are a crucial food source for whales, seals, and penguins. Their ability to detect predator-related chemical signals helps them survive but could also impact their availability as prey. Researchers suspect krill react to compounds in penguin guano that contain remnants of digested krill and fish. Similar responses may occur around other predators, such as seals and whales.

Future implications

With climate change shifting krill populations southward, understanding how these chemical cues affect their behaviour is crucial. Changes in krill movement and feeding can have widespread effects on Antarctic ecosystems. The team plan to further investigate how these responses might vary in open waters and under changing ocean conditions.