Flow History Explains Temporal and Spatial Variation of Carbon Fractionation in Stream Periphyton

• Published in: Limnology and oceanography 2005-03, Vol.50 (2), p.706-712
• Main Authors: Singer, Gabriel A., Panzenböck, Michaela, Weigelhofer, Gabriele, Marchesani, Christina, Waringer, Johann, Wanek, Wolfgang, Battin, Tom J.
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Carbon isotopes; Flow velocity; Food webs; Fractionation; Freshwater; Isotopes; Periphyton; Primary productivity; Signatures; Streams
• ISSN: 0024-3590; 1939-5590
• DOI: 10.4319/lo.2005.50.2.0706

We investigated factors that contribute to isotopic carbon fractionation in periphytic biofilms in a human-altered headwater stream with a flashy hydrograph. Water velocity had an important effect on periphyton δ 13C, explaining both temporal and spatial variation. We found that water velocity averaged over a certain period before sampling, rather than the instantaneous water velocity, explained a high percentage of both temporal and spatial variation of the periphyton δ 13C signature. The relationship between water velocity and periphyton δ 13C signature was particularly influenced by individual flow events during the recent flow history. A simple model based on a flow history of 3-4 weeks reliably estimated the δ 13C signature of periphyton from distinct reaches. The model clearly identified signature shifts caused by the deposition of activated sludge particles from a wastewater treatment plant onto the periphytic biofilms. We highlight the high spatial and temporal variability of periphyton δ 13C signatures (i.e., up to 3-6‰) in a heterogeneous flow environment with inputs from a wastewater treatment plant, and we explore its implications for food web analysis.