Tuesday, May 27, 2008
240

Angler activity as a localized impact on in-stream metabolism and insect drift in a pristine Alaska river

Nicholas R. Ettema1, Jeffrey C. Davis2, Gay A. Davis2, and Eric Snyder1. (1) Biology, Grand Valley State University, 207 Henry Hall, 1 Campus Dr., Allendale, MI 49401, (2) Aquatic Restoration and Research Institute, P.O. Box 923, Talkeetna, AK 99676

Shoreline anglers and boat traffic can negatively affect riparian vegetation and reduce bank stability.  Sediment inputs and increased turbidity from eroded banks may decrease primary production, causing changes in macroinvertebrate and fish communities.  We quantified potential recreational impacts using measures of community metabolism and drift.  Dissolved oxygen and turbidity were measured continuously in 5 day intervals at reference and impacted sites on the Little Susitna River, in south-central Alaska (June to August 2007).  Seston samples indicated that suspended sediment and organic matter were greater at impacted sites compared to reference sites. Mean values (± S.E.) for community respiration (24 hr) and gross primary production (day-length) were higher at reference vs. impacted sites (-1.04 (± 0.06) vs. -1.15 (± 0.15) and 0.84 (± 0.1) vs. 1.29 (± 0.23), respectively) (g O2 m-2; single station, open system).  Net daily metabolism was negative at impacted sites (-0.16 ± 0.11) and positive at reference sites (0.15 ± 0.11).  Turbidity was higher at impacted sites, up to 17 NTU above baseline conditions.  Changes in suspended sediment due to increased erosion or resuspension of sediment deposits could explain reduced productivity and could ultimately lead to a localized decline in salmon bioproductivity and potentially recruitment.   


Web Page: disturbance, turbidity, production

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