Carrie Harris, Ph.D. Student

Carbon Transformations in McMurdo Dry Valley lakes

Carrie is working as part of the Longterm Ecological Research (LTER) project in the McMurdo Dry Valley lakes. 

The LTER has been monitoring phytoplankton production during the austral summer at several ice-covered Antarctic lakes for over 20 years. To predict daily phytoplankton production during the entire year, I used daily under-ice light data to create a model that predicts daily phytoplankton production based on available light. These primary production predictions can be integrated throughout the water column and scaled to lake basin size to estimate annual primary production in each lake. We can compare changes to annual predicted primary production to changes in local climate and hydrology to determine how concomitant changes to environmental conditions are effecting primary productivity.

While we know a lot about how much carbon is produced in each lake, we know less about the fate of that carbon. During the 2018/19 field season, I will conduct a series of mineralization experiments that will measure bacterial community mineralization rates using radiolabeled phytoplankton detritus (particulate and dissolved) as substrates. This will help us determine how much of the carbon produced by in situ phytoplankton communities is respired at different depths in the water column. I will also measure bacterial mineralization of stream microbial mat material as an allocthonous organic carbon source. These mats are flushed into surface waters of the lake during high stream flow events.
 

--This project is funded by the National Science Foundation, Office of Polar Programs. 

Kim Roush, M.Sc. Student

Geochemical Characterization of a Sediment Core at the Grounding Zone of the Whillans Ice Plain

Kim is looking at geochemical variations throughout the extent of a 70-cm sediment core extracted from beneath 800 m of ice at the grounding zone where the Ross Ice Shelf overlies the Ross Sea and continental sediment.  Located ~110 km east of freshwater Subglacial Lake Whillans, grounding zone data will help us to constrain our understanding of hydrologic connectivity and nutrient availability.

 

    Kim Overview Map

Map of the grounding zone study area.  R2/G2 (in red) designates the drill site and sampling location of the 70 cm sediment core.  The white dashed line to the west leads to Subglacial Lake Whillans, a freshwater lake, which is hypothesized to influence the grounding zone.   

Kim GCZSCross section of the grounding zone, where the Ross Sea, Ross Ice Sheet and continental sediment convene.  The borehole shows where 800 m of ice is penetrated to sample sediment.

Kim Core

Kim holds a section of the sediment core from the grounding zone. ---Our first dropstone!! In cutting sediment cores, you're bound to run into a dropstone now and then.  Any guesses on what kind of clay we'll find here?!

--This project is funded by the National Science Foundation, Office of Polar Programs.