Temporal food web variability in an upper Missouri River backwater: energyorigination points and transfer mechanisms

Energy transfer mechanisms often cannot be identified with either an isotop e or a food habits analysis; however, a combined assessment provided collab orative support for depicting backwater food webs. Lateral dimensions in ri verine function substantially influence backwater ecology; however, backwat er communities are highly dynamic and infrequently investigated due to logi stical difficulties. We created seasonal food webs for an upper Missouri Ri ver backwater using a combined food habits and stable isotope analysis. Tem poral transition of energy origins was apparent. In the spring, carbon prim arily originated from sediments, detritus and periphyton. During mid-summer , carbon was derived from a variety of sources, but included large proporti ons of terrestrial plants and particulate organic matter. By early fall, th e backwater was uncoupled from the river, and autochthonous phytoplankton a ppeared to be the dominant carbon source. During all sample periods, Chiron omidae was an important trophic link conveying energy from the primary prod ucers to the higher consumers. Additionally, zooplankton were an important energy transfer taxa to the abundant age-0 fish community in the fall, and Corixidae were important in the spring.