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Aquatic Microbial Ecology

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AME 36:189-194 (2004)  -  doi:10.3354/ame036189

Stream food web fueled by methane-derived carbon

Ayato Kohzu1,*, Chika Kato2, Tomoya Iwata3, Daisuke Kishi2, Masashi Murakami2, Shigeru Nakano1, Eitaro Wada4

1Center for Ecological Research, Kyoto University, 509-3 Otsuka, Kamitanakami-Hirano, Otsu, Shiga 520-2113, Japan
2Tomakomai Research Station, Hokkaido University, Takaoka, Tomakomai, Hokkaido 053-0035, Japan
3Department of Ecosocial System Engineering, Yamanashi University, 4-3-11 Takeda, Kofu, Yamanashi 400-8511, Japan
4Research Institute for Humanity and Nature (RIHN), 335 Takashima-cho, Kyoto 602-0878, Japan

ABSTRACT: Food webs driven by energy from the oxidation of methane are now recognized to be omnipresent in terrestrial and freshwater ecosystems (e.g. lakes, soils and peat bogs), as well as in deep-sea hydrothermal vents and cold seeps. However, the incorporation of methane-derived carbon into stream food webs has never been reported. Here we present the first circumstantial evidence from stable carbon and nitrogen isotope ratios that a stream food web composed of aquatic macroinvertebrates is partly sustained by methanotrophs or chemoautotrophs that gain carbon respired by methane-oxidizing bacteria. Methane-derived carbon seems to enter stream communities around anoxic habitats such as backwater pools and hyporheic zones. Because these reductive habitats exist in many streams, food webs partly sustained by methane-derived carbon are likely to be ubiquitous in lotic ecosystems.

KEY WORDS: Backwater pool · Carbon isotope ratio · Hyporheic zone · Macroinvertebrates · Methane gas · Methanotrophic bacteria · Nitrogen isotope ratio · Stream food web

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