Sediment‐associated organic matter sources and sediment oxygen demand in a Special Area of Conservation (SAC): a case study of the River Axe, UK

Collins, Adrian, Zhang, Y, McMillan, Simon, Dixon, Elizabeth, Stringfellow, Anne, Bateman, Samantha and Sear, David (2017) Sediment‐associated organic matter sources and sediment oxygen demand in a Special Area of Conservation (SAC): a case study of the River Axe, UK. River Research and Applications. (doi:10.1002/rra.3175).

Abstract

Oxygen demand in river substrates providing important habitats for the early life stages of
aquatic ecology, including lithophilous fish, can arise due to the oxidation of sediment‐associated organic matter. Oxygen depletion associated with this component of river biogeochemical cycling, will, in part, depend on the sources of such material. A reconnaissance survey was therefore undertaken to assess the relative contributions from bed sediment associated organic matter sources potentially impacting on the River Axe Special Area of Conservation (SAC), in SW England. Source fingerprinting, including Monte Carlo uncertainty analysis, suggested that the relative frequency‐weighted average median source contributions ranged between 19% (uncertainty range 0–82%) and 64% (uncertainty range 0–99%) for farmyard manures or slurries, 4% (uncertainty range 0–49%) and 35% (uncertainty range 0–100%) for damaged road verges, 2% (uncertainty range 0–100%) and 68% (uncertainty range 0–100%) for decaying instream vegetation, and 2% (full uncertainty range 0–15%) and 6% (uncertainty range 0–48%) for human septic waste. A reconnaissance survey of sediment
oxygen demand (SOD) along the channel designated as a SAC yielded a mean SOD5 of 4 mg O2 g−1 dry sediment and a corresponding SOD20 of 7 mg O2 g−1 dry sediment, compared with respective ranges of 1–15 and 2–30 mg O2 g−1 dry sediment, measured by the authors for a range of river types across the UK. The findings of the reconnaissance survey were used in an agency (SW region) catchment appraisal exercise for informing targeted management to help protect the SAC.

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Contributors

Author: Anne Stringfellow

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