Methane-carbon budget of a ferruginous meromictic lake and implications for marine methane dynamics on early Earth

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2024-01-05
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Akam, Sajjad A.
Chuang, Pei-Chuan
Katsev, Sergei
Wittkop, Chad
Chamberlain, Michelle
Dale, Andrew W.
Wallmann, Klaus
Heathcote, Adam J.
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Geological Society of America
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Geological and Atmospheric Sciences
Abstract
The greenhouse gas methane (CH4) contributed to a warm climate that maintained liquid water and sustained Earth’s habitability in the Precambrian despite the faint young sun. The viability of methanogenesis (ME) in ferruginous environments, however, is debated, as iron reduction can potentially outcompete ME as a pathway of organic carbon remineralization (OCR). Here, we document that ME is a dominant OCR process in Brownie Lake, Minnesota (midwestern United States), which is a ferruginous (iron-rich, sulfate-poor) and meromictic (stratified with permanent anoxic bottom waters) system. We report ME accounting for ≥90% and >9% ± 7% of the anaerobic OCR in the water column and sediments, respectively, and an overall particulate organic carbon loading to CH4 conversion efficiency of ≥18% ± 7% in the anoxic zone of Brownie Lake. Our results, along with previous reports from ferruginous systems, suggest that even under low primary productivity in Precambrian oceans, the efficient conversion of organic carbon would have enabled marine CH4 to play a major role in early Earth’s biogeochemical evolution.
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This article is published as Sajjad A. Akam, Pei-Chuan Chuang, Sergei Katsev, Chad Wittkop, Michelle Chamberlain, Andrew W. Dale, Klaus Wallmann, Adam J. Heathcote, Elizabeth D. Swanner; Methane-carbon budget of a ferruginous meromictic lake and implications for marine methane dynamics on early Earth. Geology 2024; doi: https://doi.org/10.1130/G51713.1. © 2024 The Authors.

This paper is published under the terms of the CC-BY license.
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