Assessing 35 years of lake trophic state change in 55,000 lakes across the contiguous US

Lakes are integrators of autochthonous and allochthonous processes. Eutrophication and dystrophication are examples of how changes to autochthony and allochthony can lead to shifts in trophic state. Despite being a fundamental limnological metric, understanding the broad spatial and temporal patterns of trophic state and its drivers has been limited. To this end, we combined Landsat optical reflectance values with in situ true color and phosphorus data from the U.S. Environmental Protection Agency's National Lake Assessment to build classification models of trophic state. We applied those models to 55,662 lakes across the contiguous U.S. from 1984 to 2020, and then related regional trophic state change with a suite of hydrologic, climatic, terrestrial, biological, and atmospheric deposition predictors. Over the 35 years, we found that the majority of lakes greater than 10 ha in the US are consistently mixotrophic/eutrophic (~55%), yet dystrophic lakes have substantially increased nationally. This “brownification” trend is concentrated in the Upper Midwest and Northern Appalachian regions and may be associated with diverging mechanisms. Whereas browning in the Northern Appalachians is associated with wetland cover and acid rain legacy, the Upper Midwest browning trends appear more associated with wetland cover, warming air temperatures, and increasing precipitation. Together, these results support previous findings at regional and national scales and suggest that varied, complex drivers may be causing this change.

Primary Presenter: Michael Meyer, U.S. Geological Survey (mfmeyer@usgs.gov)

Authors:

Simon Topp, Upstream Tech  (simon@upstream.tech)

Tyler King, US Geological Survey  (tvking@usgs.gov)

Robert Ladwig, Aarhus University  (rladwig@ecos.au.dk)

Rachel Pilla, Oak Ridge National Laboratory  (pillarm1@ornl.gov)

Hilary Dugan, University of Wisconsin  (hdugan@wisc.edu)

Jack Eggleston, US Geological Survey  (jegglest@usgs.gov)

Stephanie Hampton, Carnegie Institution for Science  (shampton@carnegiescience.edu)

Dina Leech, Longwood University  (leechdm@longwood.edu)

Isabella Oleksy, Colorado University - Boulder  (isabella.oleksy@colorado.edu)

Jesse Ross, US Geological Survey  (jross@usgs.gov)

Matthew Ross, Colorado State University  (mrvr@colostate.edu)

R Iestyn Woolway, Bangor University  (iestyn.woolway@bangor.ac.uk)

Xiao Yang, Southern Methodist University  (xnayang@smu.edu)

Jill Baron, US Geological Survey  (jill_baron@usgs.gov)

Matthew Brousil, Colorado State University  (matthew.brousil@colostate.edu)

Kate Fickas, Esri  (kfickas@esri.com)

Julie Padowski, Washington State University  (julie.padowski@wsu.edu)

Amina Pollard, US Environmental Protection Agency  (pollard.amina@epa.gov)

Jianning Ren, National University of Singapore  (Jren@nus.edu.sg)

Jida Wang, University of Illinois - Urbana Champaign  (jidaw@illinois.edu)

Jacob Zwart, US Geological Survey  (jzwart@usgs.gov)