How the Scent of Penguin Guano Sparks an Escape Response in Antarctic Krill
Imagine seeing the world through the stalked compound eyes of krill in the vast Southern Ocean. Suddenly, a torpedo-like predator—an Adélie penguin—dives in, consuming thousands of krill in mere moments. But what if krill could sense the danger before the attack? New research reveals that the chemical signals in penguin poop are enough to trigger frantic escape behaviors in Antarctic krill.
The Study: Penguin Guano Alters Krill Behavior
A groundbreaking study published in Frontiers in Marine Science has shown, for the first time, that a small amount of Adélie penguin guano can drastically alter the swimming and feeding patterns of krill. According to Dr. Nicole Hellessey, a postdoctoral researcher at the Bigelow Laboratory for Ocean Sciences, “Our research demonstrates that even a trace of penguin guano causes Antarctic krill to increase their movement speed and reduce feeding activity.”
As a keystone species in the Antarctic food chain, krill serve as primary sustenance for a wide range of marine life, from whales to seabirds. However, climate change, sea ice loss, and ocean acidification are forcing krill populations to migrate further south, impacting the entire ecosystem.
Krill React to Chemical Cues in Water
Zooplankton like krill rely on chemical cues to detect food, mates, and threats. Researchers sought to understand whether krill could detect predator-related odors and adjust their behavior accordingly. The team focused on Adélie penguins, whose diet consists of 99.6% krill, consuming up to 1.6 kg per day. Globally, Adélies consume approximately 1.5 million tons of krill annually.
In late 2022, scientists aboard research vessels Laurence M. Gould and Nathaniel B. Palmer collected live krill from the Bransfield Strait and transported them to Palmer Station’s research aquarium. They also gathered 78 grams of Adélie guano from a colony on Torgersen Island.
Experiment: How Krill Respond to Penguin Poo
To assess the impact of penguin guano on krill behavior, researchers placed six to eight krill in a seawater flume at 1.5°C for five-minute trials. The water was infused with either algae, penguin guano, or a combination of both. Video recordings analyzed krill movement, speed, and direction in different conditions.
Key Findings:
- Krill exhibited rheotaxis (swimming upstream) in normal conditions.
- Upon exposure to guano, krill increased swimming speed by 1.2 to 1.5 times and changed direction three times more frequently.
- Krill reduced algae consumption by 64% when exposed to penguin guano, indicating heightened alertness and disrupted foraging.
- The erratic, zigzagging movement suggested an instinctive escape response.
Dr. Hellessey explains, “Such escape behavior significantly boosts krill survival chances. In a swarm, their collective response could exponentially increase their odds of evading predators.”
What’s Inside Penguin Guano? The Mystery Continues
While the study confirms that krill react to penguin waste, the exact chemicals responsible remain unknown. Scientists hypothesize that krill might be detecting the scent of digested krill and fish in the guano. If true, this behavior could extend to other predators like seals and whales.
Future research will explore how krill’s ability to sense these chemical cues changes in open waters and under climate change conditions. Given their crucial role in the Southern Ocean ecosystem, any shift in krill behavior could have far-reaching consequences.
Final Thoughts: Why This Matters
Understanding krill’s response to predator cues is essential for predicting ecosystem changes in Antarctica. As climate change alters ocean conditions, the survival strategies of krill—and the species that depend on them—will be critical to maintaining balance in the marine food web.
This study highlights the intricate relationships within marine ecosystems and underscores the need for continued research to safeguard Antarctic biodiversity.