Marine Science Schweppe Seminars

Friday, November 18, 11:00 am, In-person & Zoom.
UT Marine Science Institute, Patton Center, Auditorium

"The Importance of an Unimportant Lake at the Bottom of the World"

Brad Rosenheim, Ph.D.
Associate Professor, College of Marine Sciences, University of South Florida.

Seminar summary: As 2018 turned to 2019, a group of scientists cleanly accessed an isolated ecosystem residing in a lake beneath 1100 m of ice only 500 km from the South Pole. The project, Subglacial Antarctic Lakes Scientific Access (SALSA), succeeded in sampling the Mercer Subglacial Lake’s (SLM) water column without microbial contamination, retrieved the longest composite sediment core from a subglacial lake, and isolated delicate laminations at the sediment-water interface indicative of a history of lacustrine deposition. These samples from SLM hold microbial clues to the history of ice cover in the ice plain poleward of the Siple Coast. A recent Holocene incursion of marine seawater charged a microbial chemolithoautotrophic battery that keeps the ecosystem alive at least 6,200 years after the incursion. This system now remineralizes organic matter from lake sediments to provide energy for the isolated ecosystem, leaving isotopic indicators of metabolic rates in the dissolved carbon of the water column. These isotopic indicators tell us that the lake is relatively unimportant; metabolism of organic matter is happening over an area one order of magnitude larger than the lake in the interconnected subglacial hydrologic system and this area delineates the extent of the last marine incursion. Although we determined that the ephemeral lake is not the focus of microbial activity, the presence of laminated sediment give us a new understanding of ice thickening and dynamics of Antarctic ice streams. The picture emerging from SALSA is that Antarctic ice is more sensitive to climate and other variables than previous thought.

Host: Dr. Zhanfei Liu

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