PONDS AND SMALL, SHALLOW LAKES AS HOTSPOTS OF ORGANIC CARBON CYCLING ACROSS PERMAFROST GRADIENTS

Across Arctic and boreal regions, anthropogenic activity is responsible for increasing temperatures, vegetation expansion, and permafrost thaw. Ponds and shallow lake areas are increasing across permafrost influenced environments, potentially augmenting regional carbon cycling. These very small water bodies are tightly linked to the land, making them highly responsive to environmental changes driven by anthropogenic activity. To monitor seasonal changes in dissolved organic matter (DOM) composition in ponds and small, shallow lakes, we collected biweekly surface water samples at 12 sites across a gradient of underlying permafrost, ground-ice content, and soil organic carbon near Fairbanks, Alaska. We operationally defined ponds as bodies with surface area less than .01 km² and shallow lakes as greater than or equal to 0.01 km², and less than 5 meters in depth. We measured dissolved organic carbon concentrations, DOM absorbance and fluorescence, and water isotopes as a proxy for hydrologic connectivity to assess the variability in DOM composition across heterogeneous landscapes and hydrologic connectivity. Composition was variable across sites and seasons; in small lakes DOC and absorbance at 254 nm were strongly correlated whereas ponds seasonally deviated from the relationship. We also found that DOM composition changed significantly across the seasons and interannually indicating that these sites are extremely responsive to the environmental condition.

Primary Presenter: Emily Peterson, University of Alaska Fairbanks (peterson.emily238@gmail.com)

Authors:

Emily Peterson, University of Alaska Fairbanks  (egpeterson@alaska.edu)

Paige Kehoe, University of Alaska Fairbanks  (pkehoe2@alaska.edu)

Ryan Owens, University of Alaska Fairbanks  (rpowens@alaska.edu)

Iva Thomason, University of Alaska Fairbanks  (imthomason@alaska.edu)

Sarah Johnston, University of Alaska Fairbanks  (sejohnston2@alaska.edu)