Tuesday, June 5, 2007
484

Quantifying energy flow to aquatic food webs in the Colorado River using stable isotopes of hydrogen (dD)

Melanie Caron1, Richard R. Doucett1, and John L. Sabo2. (1) Colorado Plateau Stable Isotope Laboratory, Merriam-Powell Center for Environmental Research, Northern Arizona University, South Beaver Street, Building 21, Flagstaff, AZ 86011-5640, (2) School of Life Sciences, Arizona State University, Tempe, AZ 85287

Distinguishing between terrestrial and aquatic sources of energy to river food webs is central to stream ecosystem and community theory.  Currently, there is no universally reliable technique for separating these energy sources in river food webs. In some cases, stable isotopes of carbon (d13C) are sufficiently different in leaves (allochthonous) and algae (autochthonous) to trace their relative importance in aquatic food webs. In others, however, d13C values do not differ sufficiently between leaves and algae, or d13C variation is too high.  Here, we present data suggesting that stable isotopes of hydrogen (dD) can be used to trace energy flow and differentiate between terrestrial and aquatic inputs contributing to the aquatic food web. We found that autochthonous organic matter (OM) is uniformly more depleted in deuterium (lower dD values) than allochthonous OM, an average difference of over 100‰. We also found that organisms at higher trophic levels (invertebrates, fish) have dD values intermediate between aquatic algae and terrestrial plants. The consistent differences between leaves and algae in dD, along with intermediate values in higher trophic levels, indicate that dD isotopic signatures are a powerful tool for partitioning energy flow in aquatic ecosystems.

See more of Poster Session - Food Webs
See more of Contributed Sessions

See more of The NABS 55th Annual Meeting