Studying the past, and predicting the future, of the Southern Ocean food web

Last week, GSO professor Kelton McMahon returned to the Antarctic to join several colleagues on a research cruise. The expedition is part of a multi-year project intended to help scientists better understand how the Southern Ocean food web has responded to environmental changes in the past, and predict how the ecosystem might respond to a changing climate in the future. Before he departed, we caught up with Dr. McMahon to learn more about the project, why penguins are so valuable for understanding environmental change, and how he and several GSO students will analyze the samples he brings back to Rhode Island. We’ll be posting updates to this page, and be sure to keep an eye on GSO’s Instagram, Twitter, and Facebook pages for the latest on this project!

First of all, why are you heading to Antarctica? What’s the goal of your project?

This research cruise to Antarctica is part of a multi-year National Science Foundation-funded project to investigate decadal and millennial-scale variations in food web structure and population dynamics of krill predators in the Southern Ocean. The Antarctic Peninsula is warming significantly faster than the global average, bringing with it potentially profound changes in the sources and cycling of organic matter in the region. I am working with colleagues from the U.S. and abroad to study how these environmental changes have altered the food web structure that supported Antarctic krill predators in the past as a tool to help us predict future ecosystem responses to our changing climate.

Your research connects penguins to historic whaling and recent climate change. That’s a wide-ranging story. Why are penguins so central to your work?

Penguins are amazing, charismatic creatures that serve as sentinel species for environmental change. They occupy a central node in the Southern Ocean food web, recording geochemical clues about their diet and migration patterns in their tissues. We will be comparing the isotope values of modern penguin tissues to historic samples from museum archives to test hypotheses about how both historic whaling in the 1800s and early 1900s and rapid warming in the past century have altered the food web structure and population dynamics of Antarctic penguins. We are also conducting paleontological excavations to collect penguin feathers and eggshells that are hundreds to thousands of years old to provide a long-term historical context to the rapid changes in food web structure we see today.

This is not your first trip to the Antarctic. What have you learned from previous trips, and what do you hope to learn this time around?

We found that food web architecture in the Southern Ocean has undergone some amazing changes over the last 10,000 years. We’ve seen dramatic shifts in productivity and biogeochemical cycling at the base of the food web linked to changes in regional climate. We’ve also seen changes in the trophic dynamics of penguins foraging within these shifting food webs over the last several hundred years. Our hope is to increase the temporal resolution of our samples back through time so that we can better constrain the timing of these shifts, particularly as they relate to recent rapid warming historic whaling in the 1800s and 1900s.

Once you’ve gathered your samples and return home to the lab, what are the next steps?

Once we return home, I’ll first kiss my wife and say hi to my puppies. Then it’s back to the newly built Ocean Ecogeochemistry Laboratory at GSO, where my students and I will be conducting molecular isotope geochemistry on the penguin feathers and eggshells we collected during the trip. Once we radiocarbon date the samples, we will analyze their carbon and nitrogen isotope values of amino acids. These analyses will reveal a rich history of the sources and cycling of organic matter in the Southern Ocean over tens to thousands of years.

You’ll be on board a ship with your colleagues and also with tourists, so I imagine that’s not the typical working day at sea for you?

We have a fantastic partnership with the adventure tour company Quark Expeditions. Through this partnership, we send members of our team on cruises throughout much of Antarctica during the spring, summer, and fall, which would otherwise be nearly impossible to achieve through traditional scientific research cruises. In exchange, we engage with tourists from around the world through lectures and guided expeditions to educate them about the ecosystems of Antarctica and the results of our research. This partnership is made possible by, a citizen science initiative that supports Southern Ocean research, education, and outreach.

Thanks, and we’ll look forward to getting your updates from the field!


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A lone gentoo penguin calls for its mate in the frenzy of reunions as penguins return to shore on Carcass Island, Falkland Islands. @universityofri GSO professor Kelton McMahon and @LSU professor Michael Polito have been on the Falkland Islands as part of their research to quantify the distribution and abundance of #penguins throughout the Southern Ocean. Swipe for more pics of gentoo penguins emerging from the ocean after feeding at sea for several days, as well as a curious young magellanic penguin exploring McMahon’s and Polito’s gear bags as they prepare to hike to their field site on West Point Island. The team is currently exploring the Southern Ocean aboard the @quarkexpeditions M/V Ocean Endeavour, follow us for updates! . . #NSFfunded #wildlife #oceanography #exploremore #Antarctica #oceanografia

A post shared by URI GSO (@uri.gso) on Mar 4, 2019 at 8:29am PST