Increasingly severe wildfires release smoke plumes covering entire continents, depositing aerosols and reducing solar radiation fluxes to millions of lakes, yet little is known about impacts on inland waters. This large-scale study we 1) quantified annual and seasonal trends in the spatial extent of smoke cover in California, USA (2006 - 2022), and 2) assessed the impacts of smoke on gross primary production (GPP) and ecosystem respiration (R) in 10 lakes spanning a large gradient in trophic status, during the three smokiest years since 2006 (2018, 2020, 2021). The maximum spatial extent of medium or high-density smoke cover between June - October has increased to 70% of California’s area, with the greatest increases in August and September. In the three smokiest years, lakes experienced an average of 33 days of smoke between July and October, resulting in substantial reductions in shortwave radiation fluxes and 4 to 5-fold increases in atmospheric fine particulate matter concentrations (PM2.5). R decreased during smoke cover in oligotrophic lakes but not in eutrophic lakes, whereas responses of lake GPP were extremely variable. Effects of prolonged smoke exposure on inland waters will vary substantially due to mediating effects of lake attributes and seasonal timing of wildfires.

Authors:

Adrianne Smits, University of California Davis  (asmits@ucdavis.ed)

Facundo Scordo, Instituto Argentino de Oceanografía, Universidad Nacional del Sur (UNS)-CONICET  (scordo@agro.uba.ar)

Minmeng Tang, Cornell University  (mt747@cornell.edu)

Alicia Cortes, University of California Davis  (alicortes@ucdavis.edu)

Mary Jade Farruggia, University of California Davis  (mjfarruggia@ucdavis.edu)

Joshua Culpepper, York University  (joshua.culpepper7@gmail.com)

Sudeep Chandra, University of Nevada Reno  (sudeep@unr.edu)

Yufang Jin, University of California Davis  (yujin@ucdavis.edu)

Sergio Valbuena, University of California Davis  (savalbuena@ucdavis.edu)

Shohei Watanabe, University of California Davis  (swatanabe@ucdavis.edu)

Geoff Schladow, University of California Davis  (gschladow@ucdavis.edu)

Steven Sadro, University of California Davis  (ssadro@ucdavis.edu)