Title:

Investigating the Relationship Between Ebullition and  Methane Production in Arctic Lakes, Stordalen Mire, Sweden

Arctic lakes are major sources of atmospheric methane emissions and are sensitive to changing temperatures. As these ecosystems experience up to 4x the warming of other regions, an increase in methane (CH4) emissions is expected. There are multiple pathways through which CH4 from lakes is released to the atmosphere, but CH4 release is primarily driven by CH4 bubbles emitted from the sediments (i.e. ebullition). Despite ebullition being the dominant form of CH4 release from lakes, ebullitive measurements are still under-represented and sediment production rates are rarely paired with fluxes. The purpose of this study is to analyze the relationship between ebullition rates and sediment CH4 production in three, post-glacial lakes near Stordalen Mire, Northern Sweden (68◦220 N, 19◦030 E). From June- August 2023 we measured ebullitive fluxes, sediment CH4 production from incubations, water column and sediment temperatures, and water quality parameters across the lakes over a range of depths and aquatic vegetation types. The net ebullitive emissions will be compared to historical data collected at the lakes. We will explore correlations between the quantity and rate of methane release from ebullition and production rates in sediments across depth and edge/vegetation to center gradients. We will also examine how production rates could change with rising lake temperatures using ex-situ sediment incubations at 15 ℃ and 20 ℃. We hypothesize that (1) there would be a strong positive relationship between CH4 emission in the field and production rates in the incubations, due to the fact that methane is produced dominantly in the sediment before being released as bubbles to pass through the water column, (2) CH4 production would increase under warmer temperatures due to increased methanogen activity, and (3) ebullition would vary across the lake gradients, with the greatest emissions located in shallow or edge/more vegetated areas, due to warmer temperatures and an increase in carbon input. This research will contribute to understanding the impact of warming on lake ecosystems in the Arctic and of methane cycling in lakes.

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