The Metabolic Balance of Lake Superior’s Mixed Layer

Understanding carbon (C) dynamics in large lake ecosystems presents significant challenges due to their size, limiting our understanding of their role in the global C cycle. Here, we used autonomous underwater vehicles (gliders) to calculate metabolism in Lake Superior, the world’s largest freshwater lake by surface area. We used seven years of high-resolution limnological data from 17 glider missions, including dissolved oxygen and temperature, along with wind data from the National Data Buoy Center, to calculate daily epilimnetic gross primary production (0.32 ± 0.49 g O2 m^-3 day^-1) and ecosystem respiration (0.50 ± 0.60 g O₂ m^-3 day^-1) using established methods. Our findings revealed net heterotrophy dominated in the epilimnion of Lake Superior, with net ecosystem production recorded at 0.17 ± 0.53 g O₂ m^-3 day^-1, displaying spatial and temporal variations. Despite relatively lower metabolic rates than other lake ecosystems, Lake Superior's substantial size significantly contributes to the global C cycle. This study showcases the unexploited potential of gliders in advancing our understanding of C dynamics in large lake ecosystems.

Primary Presenter: Panditha Gunawardana, Trent University (sasindugunawardana@trentu.ca)

Authors:

Nolan Pearce, Trent Univerisity  (nolanpearce@trentu.ca)

Jay Austin, University of Minnesota  (jaustin@d.umn.edu)

Thomas Hollenhorst, United States Environmental Protection Agency  (Hollenhorst.Tom@epa.gov)

Marguerite Xenopoulos, Trent University  (mxenopoulos@trentu.ca)