Metabolism in lake pelagic and littoral habitats respond differently to smoke from wildfires

FACUNDO SCORDO; CHANDRA SUDEEP; STEVE SADRO; CARINA SEITZ

Encuentro; AGU Fall Meeting 2021; 2021

As the wildfire seasons are increasing worldwide, smoke from fires can have far-reaching impacts on aquatic ecosystems located away from burned areas. We lack a conceptual understanding of how ecosystem metabolic rates respond to changes in solar inputs at the habitat-specific (nearshore-littoral or pelagic) resolution. We determined the metabolic response to smoke in the pelagic and two 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 a year with smoke and three years without smoke. Smoke decreased underwater ultraviolet-B radiation by 76% and decreased photosynthetically active radiation (PAR) by 36%. During the smoke period, at the two littoral sites GPP and R resembled the non-smoke years (p > 0.05). In contrast, GPP, and NEP from the pelagic habitat were higher (p < 0.05), while R remained similar (p = 0.09) in 2018 in comparison to the non-smoke years. GPP and NEP in the pelagic habitat remained high in 2018 even 15 days after the smoke disappeared. We suggest these patterns are the result of reduced light intensity in the water column, alleviating photoinhibition. The higher light adaptation of littoral primary producers makes the metabolism of the littoral zone more resilient to the effects of smoke. Our results demonstrate habitat-specific responses of production to smoke from wildfire and underscore the potential for prolonged smoke cover to alter energy flow in lakes, with implications for food web structure.