Filamentous green algae Spirogyra regulates methane emissions from eutrophic rivers.

Dan Mei, Ming Ni, Xia Liang, Lijun Hou, Feifei Wang, Chiquan He

Environmental science and pollution research international 2021 Jan

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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 [Formula: see text] 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. Graphical abstract.

Citation

Dan Mei, Ming Ni, Xia Liang, Lijun Hou, Feifei Wang, Chiquan He. Filamentous green algae Spirogyra regulates methane emissions from eutrophic rivers. Environmental science and pollution research international. 2021 Jan;28(3):3660-3671