Dense and Prolonged Wildfire Smoke Alters Primary Production and Ecosystem Respiration in California Lakes

ADRIANNE SMITS; FACUNDO SCORDO; ALICIA CORTES; MINMENG TANG; JOSHUA CULPEPPER; STEVEN SADRO; MARY JADE FARRUGGIA; SUDEEP CHANDRA; SHOHEI WATANABE; SERGIO ALEJANDRO VALBUENA; GEOFFREY SCHLADOW; YUFANG JIN

San Francisco

Congreso; American Geophysical Union Anual Meeting; 2023

American Geophysical Union

Increasingly severe wildfires release smoke that can cover entire continents, depositing particulates and decreasing incoming solar radiation. The impacts of prolonged, dense smoke cover on aquatic ecosystems are unknown despite the large number of freshwater bodies exposed in recent years. We quantified the effects of smoke cover on daily gross primary production (GPP) and ecosystem respiration (ER) in 11 lakes in California, USA, during the three smokiest years since 2006 (2018, 2020, 2021). Our study lakes span from the Southern Sierra Nevada to the Klamath Mountains and represent a wide range in trophic states, from hyper-eutrophic Clear Lake to ultra-oligotrophic Lake Tahoe. Lakes were exposed to an average of 33 days of dense smoke during July-October, resulting in a 21% mean reduction in daily shortwave radiation, though exposure was both spatially and temporally heterogeneous. Responses of lake GPP to smoke were extremely variable among and within lakes, as well as between years. In contrast, the response of ER to smoke was related to lake trophic state and mean lake temperature–ER decreased during smoke cover in cold, oligotrophic lakes but not in warm, eutrophic lakes. Our results suggest that the impacts of smoke cover on lakes will be highly variable both within and among regions due to heterogeneous smoke exposure in time and space, as well as the mediating effects of lake attributes on thermal and metabolic responses.