caa a22 4500 445383941 CHVBK 20180317143026.0 cr unu---uuuuu 170323e20110601xx s 000 0 eng 10.1007/s10021-011-9430-1 doi (NATIONALLICENCE)springer-10.1007/s10021-011-9430-1 Carbon Cycling in Floodplain Ecosystems: Out-Gassing and Photosynthesis Transmit Soil δ13C Gradient Through Stream Food Webs [Elektronische Daten] [Duncan Gray, Jon Harding, Bo Elberling, Travis Horton, Tim Clough, Mike Winterbourn] Natural braided river floodplains typically possess high groundwater-surface water exchange, which is vital to the overall function and structure of these complex ecosystems. Spring-fed streams on the floodplain are also hotspots of benthic invertebrate diversity and productivity. The sources of carbon that drive these productive spring-fed systems are not well-known. We conducted field assessments and a manipulation, modeling, and a laboratory experiment to address this issue. Initially δ13C values of both dissolved inorganic carbon (DIC) and food-web components of five springs were used to assess the sources of carbon to spring food webs. Partial pressures of CO2 in upwelling water ranged from 2 to 7 times atmospheric pressure, but rapidly approached equilibrium with the atmosphere downstream commensurate with 13C enrichment of DIC. Speciation modeling and a laboratory out-gassing experiment suggested that downstream changes in pH could be explained solely by CO2 out-gassing. However, field results indicated that both out-gassing and photosynthetic drawdown by aquatic plants controlled the net flux of CO2. A whole stream manipulation indicated out-gassing was the primary effect at the spring source, which was confirmed by invariant diel pH. At 1296m downstream from the spring source a large diel shift in pH indicated a plant effect on CO2 concentration which would contribute to the overall downstream gradient in δ13C DIC. Within the first 1296m the gradient in δ13 DIC was transmitted through three trophic levels of the spring food web. These findings indicate dependency on groundwater inorganic carbon by spring stream food webs and strong hydrologically mediated linkages connecting terrestrial, subsurface, and aquatic components of the floodplain. Springer Science+Business Media, LLC, 2011 biogeochemistry nationallicence connectivity nationallicence carbon nationallicence braided river nationallicence food web nationallicence stable isotopes nationallicence New Zealand nationallicence Gray Duncan School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand aut Harding Jon School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand aut Elberling Bo Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen K, Denmark aut Horton Travis Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand aut Clough Tim Agriculture and Life Sciences Division, Lincoln University, PO Box 84, Canterbury, New Zealand aut Winterbourn Mike School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand aut Ecosystems Springer-Verlag 14/4(2011-06-01), 583-597 1432-9840 14:4<583 2011 14 10021 https://doi.org/10.1007/s10021-011-9430-1 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10021-011-9430-1 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Gray Duncan School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand aut NATIONALLICENCE 700 1- Harding Jon School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand aut NATIONALLICENCE 700 1- Elberling Bo Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen K, Denmark aut NATIONALLICENCE 700 1- Horton Travis Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand aut NATIONALLICENCE 700 1- Clough Tim Agriculture and Life Sciences Division, Lincoln University, PO Box 84, Canterbury, New Zealand aut NATIONALLICENCE 700 1- Winterbourn Mike School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand aut NATIONALLICENCE 773 0- Ecosystems Springer-Verlag 14/4(2011-06-01), 583-597 1432-9840 14:4<583 2011 14 10021 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer