Tuesday, May 27, 2008 - 11:15 AM
170

Pacific salmon influence whole-stream metabolism in Southeast Alaskan streams

Peter S. Levi, Jennifer L. Tank, Scott D. Tiegs, Dominic T. Chaloner, and Gary A. Lamberti. Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556

Migrations of Pacific salmon (Oncorhynchus spp.) into their natal spawning streams are widely believed to increase stream ecosystem productivity, an effect linked to marine-derived nutrients delivered via excretion and carcass decomposition.  However, recent studies indicate that salmon can decrease benthic primary producers through physical disturbance to stream sediments during migration and spawning.  These studies demonstrate contrasting ecological influences of salmon on stream productivity, but reach scale primary production has rarely been measured directly.  Therefore, we quantified whole-stream metabolism, an integrative metric of gross primary production (GPP) and community respiration (CR), along with stream physiochemical variables in 7 streams on Prince of Wales Island, Alaska before and during salmon migration.  The response to salmon was highly variable among streams with some streams showing an increase in GPP with salmon (e.g., from 0.89 to 5.07 gO2/m2/day in Maybeso Creek) while others experienced a decrease in GPP during salmon migration (e.g., from 0.48 to 0.26 gO2/m2/day in Twelve-Mile Creek).  In contrast, CR increased across most streams in the presence of salmon (e.g., from 0.80 to 3.96 gO2/m2/day in Twelve-Mile Creek).  We suggest that the physical aspects of stream ecosystems (e.g., geomorphology and sediment size) determine how spawning salmon influence stream metabolism.


Web Page: Whole-stream metabolism, production, pacific salmon

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