PARENT SESSION
Oral Session #7: Aquatic Ecology: Stream ecosystems. Presiding: T. Ehlinger.
Monday, August 6, 2001. 8:00 AM to 12:00 PM. Hall of Ideas G.
Hyporheic processing and storage of nutrients from spawning sockeye salmon.
O'Keefe, Thomas1, Edwards, Richard 2, 1 2
ABSTRACT- Evidence for the importance of marine-derived nutrient (MDN) inputs to freshwater ecosystems and the adjoining riparian zone is rapidly accumulating, but the mechanisms by which MDN inputs are stored and transferred are poorly understood. Annual inputs of MDN increase stream productivity and may result in enhanced growth rates and altered community composition in riparian forests. Since floods and animal feeding can remove carcasses and decomposition products from streams, hyporheic zone nutrient storage may be an important mechanism by which salmon-derived nutrients are retained within stream ecosystems and subsequently made available to primary producers. Uptake of enriched hyporheic waters by riparian root systems may be an important pathway for nutrient transfer to riparian vegetation. Within Lynx Creek, a sockeye spawning stream in SW Alaska, surface water moves into extensive areas of floodplain hyporheic zone along spawning reaches and flows downstream before returning to the channel. Nutrients entering the hyporheic zone are retained and transformed as they move along flow paths. While MDN are clearly important for stream ecosystems in general, the relative importance of hyporheic transfer varies with the size of the salmon run, the capacity for animals to remove carcasses from the stream, and the landscape context.
KEY WORDS: hyporheic, salmon, nitrogen, riparian