The Antarctic marine ecosystem is experiencing rapid environmental and ecological change associated with modern anthropogenic climate change and shifts in human-environment interactions, such as marine mammal conservation and a growing Southern Ocean krill fishery. These recent changes are overlain on long-term climatic variation that influences everything from ocean temperatures and sea ice extent to wind and ocean circulation. Together, these environmental, climatic, and ecological forces have had major impacts on the ecology of krill predators in the Southern Ocean. The major research goal of this collaborative project was to help place recent ecological changes in the Southern Ocean ecosystem into a larger historical context by examining decadal and millennial-scale shifts in the diet, foraging ecology, and population dynamics of Antarctic krill predators (primarily penguins). Specifically, this study recovered and analyze modern (<20 year old), historic (20-200 year old), and ancient (200-10,000 year old) biological tissues from penguins and other krill predators to track how their diet, role in the Southern Ocean food web, occupation history, and distribution have changed through time in response to past shifts in climate and the availability of Antarctic krill. To do this, we coupled advanced isotope techniques, particularly compound-specific stable isotope analysis, with unprecedented access to modern, historical (museum archive), and well-preserved paleo-archives (paleontological excavations of ancient penguin breeding colonies) of Antarctic krill predator tissues dating throughout the Holocene. We found that krill predator response to past environmental, climatic, and ecosystem shifts varied by species and foraging strategy. Generalist predators, with flexible diets and foraging strategies (e.g., gentoo penguins), showed adaptive shifts in diet in concert with changes in Antarctic krill availability following historic exploitation of marine mammals and recent climate change. Their populations and distributions along the Antarctic Peninsula have simultaneously increased in recent years, likely as function of this dietary flexibility. In contrast, specialist species (e.g., chinstrap and Adelie penguins) maintained a consistent krill diet despite changes in krill availability through time, which likely contributes to their current population declines in the northern Antarctic Peninsula. These krill predator tissues also served as millennial scale biological archives of past shifts in ecosystem productivity and biogeochemical cycling. For instance, we documented an abrupt shift in biogeochemical cycling concurrent with Late Holocene climatic events associated with the Little Ice Age, as well as a more recent coastal productivity increase in the past century, suggesting modern observations of increasing coastal productivity are part of a longer-term trend of increasing coastal productivity in the northern Antarctic Peninsula since the early 20th century. This project also identified large-scale changes in the occupation history of penguin colonies around Antarctica in response to changes in climate and sea ice conditions over the past several millennia. These findings emphasize the importance of long-term climate variability on ecological processes in the Southern Ocean. Together, this work provides long-term ecological context to better understand how Antarctic krill predators, the krill they depend on, and the greater Antarctic marine ecosystem have responded to past changes in environment, climate, and human-environment interaction in the Southern Ocean. Understanding these past changes will provide needed scientific support to better predict future population and ecosystem changes in light of current and emerging environmental challenges in the Southern Ocean.

A second major goal of this project was to support NSF?s goal of training a new generation of scientists and making scientific discoveries available and accessible to the public. As such, this project supported the cross-institutional training of undergraduate and graduate students in advanced analytical techniques in the disciplines of ecology and biogeochemistry in the classroom, the laboratory, and in the field. This project supported the research and career development of two postdoctoral scholars, one early career faculty member, four graduate students, and eight undergraduates, eleven of which identify as coming from historically minoritized communities in geosciences. In addition, this project contributed to the K-12 education of >400 second graders and >100 high school students via classroom visits, curriculum development, and satellite phone calls from Antarctica aimed at engaging students in scientific issues related to polar ecosystems, penguins, biogeochemistry, global climate change, and human-environment interactions. At the university level, this project developed hands on laboratory components and active learning modules for multiple courses at the University of California ? Santa Cruz, University of Rhode Island, and University of Utah, reaching 637 undergraduates and 89 graduate students. To engage the general public, this project developed presentations that reached an estimated 600 RI residents via an annual climate series seminar and University of Rhode Island public engagement events as well as 1,050 international ecotourists via Quark Expeditions cruises to Antarctica.

Last Modified: 05/06/2021
Modified by: Kelton Mcmahon