USAP-DC

A profound transformation in ecosystem structure and function is occurring in coastal waters of the western Weddell Sea, with the collapse of the Larsen B ice shelf. This transformation appears to be yielding a redistribution of energy flow between chemoautotrophic and photosynthetic production, and to be causing the rapid demise of the extraordinary seep ecosystem discovered beneath the ice shelf. This event provides an ideal opportunity to examine fundamental aspects of ecosystem transition associated with climate change. We propose to test the following hypotheses to elucidate the transformations occurring in marine ecosystems as a consequence of the Larsen B collapse: (1) The biogeographic isolation and sub-ice shelf setting of the Larsen B seep has led to novel habitat characteristics, chemoautotrophically dependent taxa and functional adaptations. (2) Benthic communities beneath the former Larsen B ice shelf are fundamentally different from assemblages at similar depths in the Weddell sea-ice zone, and resemble oligotrophic deep-sea communities. Larsen B assemblages are undergoing rapid change. (3) The previously dark, oligotrophic waters of the Larsen B embayment now support a thriving phototrophic community, with production rates and phytoplankton composition similar to other productive areas of the Weddell Sea. To document rapid changes occurring in the Larsen B ecosystem, we will use a remotely operated vehicle, shipboard samplers, and moored sediment traps. We will characterize microbial, macrofaunal and megafaunal components of the seep community; evaluate patterns of surface productivity, export flux, and benthic faunal composition in areas previously covered by the ice shelf, and compare these areas to the open sea-ice zone. These changes will be placed within the geological, glaciological and climatological context that led to ice-shelf retreat, through companion research projects funded in concert with this effort. Together these projects will help predict the likely consequences of ice-shelf collapse to marine ecosystems in other regions of Antarctica vulnerable to climate change. The research features international collaborators from Argentina, Belgium, Canada, Germany, Spain and the United Kingdom. The broader impacts include participation of a science writer; broadcast of science segments by members of the Jim Lehrer News Hour (Public Broadcasting System); material for summer courses in environmental change; mentoring of graduate students and postdoctoral fellows; and showcasing scientific activities and findings to students and public through podcasts.

Person	Role
McCormick, Michael	Investigator and contact
Vernet, Maria	Investigator
Van Dover, Cindy	Investigator
Smith, Craig	Investigator

Antarctic Integrated System Science	Award # 0732983
Antarctic Organisms and Ecosystems	Award # 0732983
Antarctic Integrated System Science	Award # 0732917
Antarctic Integrated System Science	Award # 0732711
Antarctic Organisms and Ecosystems	Award # 0732711
Antarctic Integrated System Science	Award # 0732450

USAP-0732917_1

None in the Database

Repository	Title (link)	Format(s)	Status
R2R	NBP1001 cruise data	Excel	exist
R2R	NBP1203 cruise data	Excel	exist
USAP-DC	LARISSA: Impact of ice-shelf loss on geochemical profiles and microbial community composition in marine sediments of the Larsen A embayment, Antarctic Peninsula	None	exist
USAP-DC	Species Abundance Data from the Larsen Ice Shelf Ice acquired during R/V Nathaniel B. Palmer expedition NBP1203	None	exists

1. Amon, D. J., Wiklund, H., Dahlgren, T. G., Copley, J. T., Smith, C. R., Jamieson, A. J., & Glover, A. G. (2014). Molecular taxonomy ofOsedax(Annelida: Siboglinidae) in the Southern Ocean. Zoologica Scripta, 43(4), 405–417. (doi:10.1111/zsc.12057)
2. Reilly, B., McCormick, M. L., Brachfeld, S., & Haley, B. A. (2020). Authigenic ferrimagnetic iron sulfide preservation due to non-steady state diagenesis: A perspective from Perseverance Drift, Northwestern Weddell Sea. (doi:10.1002/essoar.10504479.1)
3. Vernet, M., Geibert, W., Hoppema, M., Brown, P. J., Haas, C., Hellmer, H. H., … Verdy, A. (2019). The Weddell Gyre, Southern Ocean: Present Knowledge and Future Challenges. Reviews of Geophysics, 57(3), 623–708. (doi:10.1029/2018rg000604)
4. Cape, M. R., Vernet, M., Skvarca, P., Marinsek, S., Scambos, T., & Domack, E. (2015). Foehn winds link climate-driven warming to ice shelf evolution in Antarctica. Journal of Geophysical Research: Atmospheres, 120(21), 11,037–11,057. (doi:10.1002/2015jd023465)