Award: OPP-1141849

Our project was designed to track the presence, population size, diet, and genetic history of seals in the Ross Sea region of Antarctica over the past 5000 years. In particular, we wanted to know (i) if species of seals present had changed significantly over that time, and (ii) if there were concurrent environmental shifts. This work has implications for understanding the ecological tolerances of large marine mammals and may aid in conservation strategies. Over the course of two field seasons, we located more than 700 mummified and skeletal remains of seals in valleys adjacent to the Ross Sea. These seals crawled inland and died and have remained largely intact, except for wind abrasion, ever since. For each individual, we collected the following data (where possible): location, species, bone and carcass weathering indices, and length and degree of fusion of bones. Subsamples were taken for radiocarbon dating, isotopic analysis, and genetic analysis. Using data derived from these specimens, we reconstructed changes in species, population size and diet. We focus here primarily on the University of Maine portion of the project, which involved the distribution and radiocarbon age of the seals. Of the 700 seals examined, about 70% were crabeater, 27% Weddell, 3% leopard, and <1% southern elephant seals. We dated roughly 220 seals. Our data show that mummified remains are as old as ~5000 years, although are much more common since 1000 years ago. The scarcity of older specimens arises in part from environmental processes that break down the carcasses over time. However, our genetic data suggest that some of the scarcity of specimens >1000 years old also is the result of there being fewer crabeater and Weddell seals in the Ross Sea prior to 1000 years ago. Both crabeater and Weddell seals show a strong population expansion signal in the late Holocene. Moreover, our data show that the greatest numbers of crabeater, Weddells, and leopard seals occurred at the same time as a profound decrease in southern elephant seals, which prefer warmer waters. We suggest that this represents a major shift in species at~1000 years ago possibly as a result of increasing sea ice conditions. This further suggests that the Ross Sea ecosystem we see as 'normal' may have come into existence only about 1000 years ago. This has implications for future changes in the ecosystem under projected climate warming. The broader impacts of our work include the training of both graduate and undergraduate students in field and laboratory techniques. A graduate student and two undergraduates from the University of Maine participated in the Antarctic field work. The graduate student wrote a thesis related to the project. A second graduate student learned laboratory techniques related to this project. In addition, one of the undergraduate students continued to work with the project after returning home. Results from this project have featured in lectures at the University of Maine, as well as in public outreach lectures to commuity organizations and K-12 students. Last Modified: 04/06/2017 Submitted by: Brenda L Hall