Stream food web fueled by methane-derived carbon

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.