Antarctica's Ross Sea is one of the most productive ocean regions on Earth, supporting vast populations of penguins and other seabirds, seals, whales, and unique fish. Understanding how this incredible ecosystem works, especially in the face of environmental change, fishing, and increasing tourism, is vital. This project, a collaboration between US and UK scientists, aimed to unravel the connections between the ocean environment – from tiny floating plants (phytoplankton) and small animals like krill – up to top predators like Adélie penguins. We focused on the Ross Sea Polynya, an area of open water surrounded by sea ice that acts as a crucial hub of life, particularly near Cape Crozier, home to one of the world's largest Adélie penguin colonies. Our work provides important insights for managing the Ross Sea Region Marine Protected Area, one of the largest protected areas on the planet.

What We Did: To study this remote and challenging environment, we used cutting-edge technology. Over the 2022-2023 Antarctic summer, we deployed advanced ocean robots called "gliders." These underwater drones traveled through the water for weeks, collecting continuous data on water temperature, salinity, oxygen, and the amount of phytoplankton (measured via chlorophyll). One glider was also equipped with sonar (active acoustics) to detect aggregations of krill and fish, the penguins' main prey. Simultaneously, we attached small tracking tags to Adélie penguins at Cape Crozier. These tags recorded where the penguins traveled to find food and how deep they dived. We also analyzed penguin diet using traditional methods and modern stable isotope analysis of feathers, which provides clues about what they ate weeks or months earlier.

What We Found (Intellectual Merit): Our integrated approach provided an unprecedented, detailed look at this Antarctic food web in action. A major discovery was an enormous and unexpected phytoplankton bloom – far larger than any previously recorded in the Ross Sea during summer. Our analysis, published in Geophysical Research Letters, suggests this massive bloom was fueled by unusually late sea ice melt, which likely released vital nutrients (like iron) into surface waters that were stable and well-lit enough for phytoplankton to thrive.

We also gained new insights into the penguins. Tracking data showed us precisely where penguins were foraging relative to the glider measurements of phytoplankton and prey. Combining this with diet analysis confirmed that while penguins eat krill, Antarctic silverfish are also a critical part of their diet, especially later in the breeding season. Interestingly, our results support the idea that the huge number of penguins at Cape Crozier may deplete food close to the colony (creating a 'foraging halo'), changing diet composition once the breeding season is over and they can leave the vicinity. This is a pattern we did not observe at a nearby smaller colony at Cape Royds.

Why It Matters (Broader Impacts): This research has several broader benefits. Understanding the links between sea ice, ocean conditions, phytoplankton blooms, and predator success is crucial for predicting how this vital ecosystem will respond to ongoing environmental changes. Our findings directly inform the management and monitoring strategies for the Ross Sea Region Marine Protected Area, helping to ensure its effectiveness.

The project also provided valuable training for the next generation of polar scientists, supporting graduate students and postdoctoral researchers who gained hands-on experience with advanced technology and Antarctic fieldwork. We provided feedback to manufacturers of the tracking tags based on their performance in extreme conditions, potentially leading to improved technology. Furthermore, data and findings are shared through public data archives and the project-associated website, www.penguinscience.com, contributing to public understanding of Antarctic science and conservation.

In conclusion, this project successfully combined advanced technology and international collaboration to reveal new insights into the complex workings of the Ross Sea ecosystem, providing critical knowledge for science, conservation, and public awareness in a rapidly changing world.

Last Modified: 04/30/2025
Modified by: Grant Ballard