Filamentous green algae Spirogyra regulates methane emissions from eutrophic rivers
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RESEARCH ARTICLE
Filamentous green algae Spirogyra regulates methane emissions from eutrophic rivers Dan Mei 1 & Ming Ni 1 & Xia Liang 1,2 & Lijun Hou 2 & Feifei Wang 1 & Chiquan He 1 Received: 22 May 2020 / Accepted: 6 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Excessive growth of filamentous green algae in rivers has attracted much attention due to their functional importance to primary production and carbon cycling. However, comprehensive knowledge of how filamentous green algae affect carbon cycling, especially the CH4 emissions from river ecosystems, remains limited. In this study, incubation experiments were conducted to examine the factors regulating CH4 emissions from a eutrophic river with dense growth of filamentous green algae Spirogyra through combinations of biogeochemical, molecular biological, and stable carbon isotope analyses. Results showed that although water dissolved oxygen (DO) in the algae+sediment (A+S) incubation groups increased up to 19 mg L−1, average CH4 flux of the groups was 13.09 μmol m−2 day−1, nearly up to two times higher than that from sediments without algae (S groups). The significant increase of sediment CH4 oxidation potential and methanotroph abundances identified the enhancing sediment CH4 oxidation during Spirogyra bloom. However, the increased water CH4 concentration was consistent with depleted water δ13 CCH4 and decreased apparent fractionation factor (αapp), suggesting the important contribution of Spirogyra to the oxic water CH4 production. It can thus be concluded that high DO concentration during the algal bloom promoted the CH4 consumption by enhancing sediment CH4 oxidation, while algal-linked oxic water CH4 production as a major component of water CH4 promoted the CH4 emissions from the river. Our study highlights the regulation of Spirogyra in aquatic CH4 fluxes and will help to estimate accurately CH4 emissions from eutrophic rivers with dense blooms of filamentous green algae.
Keywords Spirogyra . Methane emission . Methane oxidation . Algal growth stage . Stable carbon isotope
Introduction Highlights • Filamentous green algae Spirogyra regulated methane (CH4) emissions from eutrophic rivers. • High dissolved oxygen during Spirogyra bloom promoted the CH4 consumption by enhancing sediment CH4 oxidation. • Algal-linked oxic water CH4 production as a major component of water CH4 promoted the CH4 emissions. Responsible Editor: Thomas Hein Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-10754-8) contains supplementary material, which is available to authorized users. * Xia Liang [email protected] 1
School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China
2
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200244, China
Methane (CH4) emitted from freshwater ecosystem is considered an important component of the global carbon cycle (Huttunen et al. 2002; Bastviken et al. 201
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