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| Titel |
Multi-scale controls on spatial variability in river biogeochemical cycling |
| VerfasserIn |
Phillip Blaen, Marie Kurz, Julia Knapp, Clara Mendoza-Lera, Joe Lee-Cullin, Megan Klaar, Jennifer Drummond, Anna Jaeger, Jay Zarnetske, Joerg Lewandowski, Eugenia Marti, Adam Ward, Jan Fleckenstein, Thibault Datry, Scott Larned, Stefan Krause |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250123735
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| Publikation (Nr.) |
 EGU/EGU2016-3039.pdf |
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| Zusammenfassung |
| Excessive nutrient concentrations are common in surface waters and groundwaters in
agricultural catchments worldwide. Increasing geomorphological heterogeneity in river
channels may help to attenuate nutrient pollution by facilitating water exchange fluxes with
the hyporheic zone; a site of intense microbial activity where biogeochemical cycling rates
can be high. However, the controls on spatial variability in biogeochemical cycling,
particularly at scales relevant for river managers, are largely unknown. Here, we aimed to
assess: 1) how differences in river geomorphological heterogeneity control solute
transport and rates of biogeochemical cycling at sub-reach scales (102 m); and
2) the relative magnitude of these differences versus those relating to reach scale
substrate variability (103 m). We used the reactive tracer resazurin (Raz), a weakly
fluorescent dye that transforms to highly fluorescent resorufin (Rru) under mildly
reducing conditions, as a proxy to assess rates of biogeochemical cycling in a lowland
river in southern England. Solute tracer tests were conducted in two reaches with
contrasting substrates: one sand-dominated and the other gravel-dominated. Each reach
was divided into sub-reaches that varied in geomorphic complexity (e.g. by the
presence of pool-riffle sequences or the abundance of large woody debris). Slug
injections of Raz and the conservative tracer fluorescein were conducted in each reach
during baseflow conditions (Q ≈ 80 L/s) and breakthrough curves monitored using
in-situ fluorometers. Preliminary results indicate overall Raz:Rru transformation
rates in the gravel-dominated reach were more than 50% higher than those in the
sand-dominated reach. However, high sub-reach variability in Raz:Rru transformation
rates and conservative solute transport parameters suggests small scale targeted
management interventions to alter geomorphic heterogeneity may be effective in
creating hotspots of river biogeochemical cycling and nutrient load attenuation. |
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