Differential effects of wildfire smoke on habitat-specific pelagic and littoral lake metabolism

FACUNDO SCORDO; STEVEN SADRO; JOSHUA CULPEPPER; CARINA SEITZ; SUDEEP CHANDRA

Grand Rapids

Congreso; Joint Aquatic Sciences Meeting 2022 in Grand Rapids, Colorado; 2022

American Fisheries Society (AFS) - Association for the Sciences of Limnology and Oceanography (ASLO) - Coastal and Estuarine Research Federation (CERF) - Freshwater Mollusk Conservation Society (FMCS) - International Association for Great Lake Research

Large wildfire complexes are an increasing phenomenon, but the impacts of wildfire smoke to lake habitats are largely unknown. We characterized the metabolic response to smoke in pelagic and littoral habitats in a mountain lake. We compared heat content, light regime, gross primary production (GPP) rate, ecosystem respiration (ER), and net ecosystem production (NEP) in years with and without smoke. Smoke decreased incident ultraviolet-B (UV-B) radiation and photosynthetically active radiation (PAR) by 53% and 28%, respectively; and particle deposition increased the extinction coefficient of UV-B and PAR within the lake by 20% and 18%, respectively. Pelagic metabolism increased during smoke cover as a result of decreased UV-B radiation. Nearshore littoral-benthic metabolism did not change, possibly reflecting adaptation to high-intensity UV-B light in these habitats. The decrease in PAR due to smoke did not reduce productivity in either of the habitats, because even during the smoke periods, midday maximum PAR intensity at depth reached values above 700 µmol m-2 s-1, light intensities that saturate productivity at two littoral and the pelagic habitats. The divergent shift in pelagic production led to the relative increase in the contribution of this habitat to whole-lake GPP. Our results highlight the importance of understanding how prolonged smoke on the landscape might alter energy flows and food web structure in lakes from lake-specific habitats.