title: Measuring terrestrial subsidies to aquatic food webs using stable isotopes of hydrogen.
abstract: Understanding river food webs requires distinguishing energy derived from primary production in the river itself (autochthonous) from that produced externally (allochthonous), yet there are no universally applicable and reliable techniques for doing so. We compared the natural abundance stable isotope ratios of hydrogen (deltaD) of allochthonous and autochthonous energy sources in four different aquatic ecosystems. We found that autochthonous organic matter is uniformly far more depleted in deuterium (lower deltaD values) than allochthonous: an average difference of approximately 100% per hundred. We also found that organisms at higher trophic levels, including both aquatic invertebrates and fish, have deltaD values intermediate between aquatic algae and terrestrial plants. The consistent differences between leaves and algae in deltaD among these four watersheds, along with the intermediate values in higher trophic levels, indicate that natural abundance hydrogen isotope signatures are a powerful tool for partitioning energy flow in aquatic ecosystems.
authors.affiliation: Colorado Plateau Stable Isotope Laboratory, Northern Arizona University, Flagstaff, Arizona 86011, USA.
authors.forename: Richard R
authors.initials: RR
authors.lastname: Doucett
authors.forename: Jane C
authors.initials: JC
authors.lastname: Marks
authors.forename: Dean W
authors.initials: DW
authors.lastname: Blinn
authors.forename: Melanie
authors.initials: M
authors.lastname: Caron
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Hungate
mesh_terms: D000818:Animals; D018533:Biomass; D003903:Deuterium / Q000032:analysis* / Q000378:metabolism*; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods; D020387:Food Chain; D008954:Models, Biological; D063245:Plant Development; D010944:Plants / Q000378:metabolism; D011157:Population Dynamics; D045483:Rivers
chemical_list: D003903:Deuterium