Wildfire Smoke Effects on Lake‐Habitat Specific Metabolism: Toward a Conceptual Understanding

Abstract

The impacts of wildfire smoke on lake habitats remains unclear. We determined the metabolic response to smoke in the epi‐pelagic and two littoral habitats in Castle Lake, California. We compared light regime, gross primary production, ecosystem respiration, and net ecosystem production in years with and without smoke. During the smoke period incident ultraviolet‐B (UV‐B) radiation and photosynthetically active radiation (PAR) decreased by 53% and 28%, respectively, while the water column extinction coefficient of UV‐B and PAR increased by 20% and 18% respectively. Epi‐pelagic productivity increased during smoke cover because of decreased solar inputs. PAR values remained sufficient to saturate productivity, suggesting observed differences were primarily the result of changes in UV‐B. Littoral‐benthic productivity did not change, possibly reflecting adaptation to high‐intensity UV‐B light in these habitats. Our results highlight the importance of understanding how prolonged wildfire smoke alters the amount of energy produced from specific habitats in lakes.

Wildfire smoke impacts lake ecosystems

“…The holistic impacts on light are characterized through the aerosol optical depth, an index for light extinction within the atmosphere (McCarthy et al, 2019;Suo-Anttila et al, 2005). Importantly, smoke attenuates electromagnetic radiation unequally, reducing light in a selective manner that decreases the ratio between ultraviolet B radiation (UV-B) and PAR (Scordo et al, 2021(Scordo et al, , 2022Williamson et al, 2016). Unsurprisingly, the effects of smoke on PAR are large and variable.…”

“…The authors theorized that the reduction in photoinhibition alone was insufficient to cause a 3-fold increase in production and hypothesized that ash deposition contributed N, P, and/or micronutrients that stimulated production. In Castle Lake (California, USA), fires burning outside the catchment resulted in smoke cover that lasted for 55 days (Scordo et al, 2021(Scordo et al, , 2022. During this period, both incident and underwater UV-B, PAR, and heat were reduced concomitant with a 109% increase in epipelagic production.…”

“…Conceptual models to date have drawn primarily from case studies of single systems, or have focused on the effects of wildfires burning within watersheds rather than the effects of smoke and ash at broader spatial scales (McCullough et al, 2019;Paul et al, 2022;Scordo et al, 2022). Our analysis addresses these critical knowledge gaps directly by: 1) quantifying lake exposure to smoke through space and time across the North American continent during three years of wildfire activity (2019 -2021); 2) reviewing the current understanding of the mechanisms by which smoke affects physical, chemical, and biological aspects of lakes; and 3) developing a conceptual framework that synthesizes known and theoretical impacts of smoke on lakes and 4) identifying research priorities for future studies.…”

Wildfire Smoke Directly Changes Biogenic Volatile Organic Emissions and Photosynthesis of Ponderosa Pines

“…Severe wildfire events have become more frequent in the last several decades (Altshuler et al., 2020) and are predicted to further increase in both frequency and intensity (Westerling et al., 2006). Although loss of life and property are the immediate concerns, the smoke released during these events can transport hazardous particles and gases thousands of kilometers and thus poses long‐term impacts to human health, air quality, and climate on local, regional, and global scales (Haque et al., 2021; Scordo et al., 2022). The terrestrial biosphere can be exposed to smoke for weeks or months in western North America (Sandberg, 2003).…”

Variable impact of wildfire smoke on ecosystem metabolic rates in lakes

“…To date, studies of smoke impacts on ecosystems focus primarily on the effects of altered radiation uxes to forest or cropland production [10][11][12] , or on the effects of aerosol deposition on phytoplankton growth in oligotrophic marine systems 6,13,14 . Existing studies of smoke effects on inland waters are limited to single site case studies (e.g., Castle Lake 8, 15 ; Lake Tahoe 16 ) or focus on relatively few response variables (e.g., water temperature 7 , cyanobacterial blooms 17 ). The in uence of smoke cover on freshwater ecosystems at spatial scales greater than single sites is not yet understood but is of growing importance, as wild res release smoke across whole continents 18 .…”