Ancient and methane-derived carbon subsidizes contemporary food webs.
While most global productivity is driven by modern photosynthesis, river ecosystems are supplied by locally fixed and imported carbon that spans a range of ages. Alluvial aquifers of gravel-bedded river floodplains present a conundrum: despite no possibility for photosynthesis in groundwater and extreme paucity of labile organic carbon, they support diverse and abundant large-bodied consumers (stoneflies, Insecta: Plecoptera). Here we show that up to a majority of the biomass carbon composition of these top consumers in four floodplain aquifers of Montana and Washington is methane-derived. The methane carbon ranges in age from modern to up to >50,000 years old and is mostly derived from biogenic sources, although a thermogenic contribution could not be excluded. We document one of the most expansive ecosystems to contain site-wide macroinvertebrate biomass comprised of methane-derived carbon and thereby advance contemporary understanding of basal resources supporting riverine productivity.
Flathead Lake Biological Station, 32125 Bio Station Lane, Polson, Montana 59860, USA.
Amanda G
AG
DelVecchia
Flathead Lake Biological Station, 32125 Bio Station Lane, Polson, Montana 59860, USA.
Jack A
JA
Stanford
University of California Irvine, Earth System Science, 2222 Croul Hall, Irvine, California 92697-3100, USA.
Xiaomei
X
Xu
D000818:Animals; D001499:Bayes Theorem; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes; D055868:Floods; D020387:Food Chain; D060587:Groundwater; D007313:Insecta; D008697:Methane / Q000378:metabolism*; D009009:Montana; D014861:Washington
D002247:Carbon Isotopes; D002244:Carbon; D008697:Methane