Seasonal persistence of marine‐derived nutrients in south‐central Alaskan salmon streams. Issue 10 (14th October 2013)

• Record Type: Journal Article
• Authors: Rinella, Daniel J.; Wipfli, Mark S.; Walker, Coowe M.; Stricker, Craig A.; Heintz, Ron A.
• Is Part Of: Ecosphere. Volume 4:Issue 10(2013)
• Page Start: 1
• Page End: 18
• Publication Date: 2013-10-14
• Subjects: Alaska -- aquatic macroinvertebrate -- Dolly Varden (Salvelinus malma) -- fatty acid -- horsetail (Equisetum fluviatile) -- Kenai Peninsula -- marine-derived nutrients -- seasonal persistence -- stable isotopes; Ecology -- Periodicals; Ecology; Periodicals; 577.05
• DOI: 10.1890/ES13-00112.1
• Languages: English
• ISSNs: 2150-8925

Abstract

Abstract : Spawning salmon deliver annual pulses of marine‐derived nutrients (MDN) to riverine ecosystems around the Pacific Rim, leading to increased growth and condition in aquatic and riparian biota. The influence of pulsed resources may last for extended periods of time when recipient food webs have effective storage mechanisms, yet few studies have tracked the seasonal persistence of MDN. With this as our goal, we sampled stream water chemistry and selected stream and riparian biota spring through fall at 18 stations (in six watersheds) that vary widely in spawner abundance and at nine stations (in three watersheds) where salmon runs were blocked by waterfalls. We then developed regression models that related dissolved nutrient concentrations and biochemical measures of MDN assimilation to localized spawner density across these 27 stations. Stream water ammonium‐N and orthophosphate‐P concentrations increased with spawner density during the summer salmon runs, but responses did not persist into the following fall. The effect of spawner density on δ 15 N in generalist macroinvertebrates and three independent MDN metrics (δ 15 N, δ 34 S, and ω3:ω6 fatty acids) in juvenile Dolly Varden ( Salvelinus malma ) was positive and similar during each season, indicating that MDN levels in biota increased with spawner abundance and were maintained for at least nine months after inputs. Delta 15 N in a riparian plant, horsetail ( Equisetum fluviatile ), and scraper macroinvertebrates did not vary with spawner density in any season, suggesting a lack of MDN assimilation by these lower trophic levels. Our results demonstrate the ready assimilation of MDN by generalist consumers and the persistence of this pulsed subsidy in these organisms through the winter and into the next growing season.