Influence of salmon spawner densities on stream productivity in Southeast Alaska

Wipfli, Mark S.; Hudson, John; Chaloner, Dominic T.; Caouette, John P.

doi:10.1139/cjfas-56-9-1600

Cited by 52 publications

(75 citation statements)

References 13 publications

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“…Thus, without spatial and temporal controls (e.g., upstream of a barrier to salmon), apparent treatment effects may be incorrectly attributed to salmon. While positive results from experimental additions of salmon material (e.g., Wipfli et al 1999;Wilzbach et al 2005, and unpublished data) lead us to doubt that salmon indeed have no effect on NO 3 and AFDM, our results suggest that effects may differ substantially depending on the use of spatial or temporal controls (e.g., Chaloner et al 2007). Accounting for both temporal and spatial variation inherent in the system increases confidence in attributing apparent treatment effects to the presence of salmon.…”

Section: Methodology Of Salmon Experiments-when Are Observations Realmentioning

confidence: 59%

“…Interestingly, effect sizes for carcass addition studies were never substantially greater than for natural salmon runs, suggesting an upper limit to the rate of nutrient mineralization and subsequent uptake and incorporation by aquatic organisms (cf. Wipfli et al 1999Wipfli et al , 2003Bilby et al 2001;Chaloner et al 2002), as well as a higher potency for live salmon than for carcasses.…”

Section: Methodology Of Salmon Experiments-when Are Observations Realmentioning

confidence: 99%

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Pacific salmon effects on stream ecosystems: a quantitative synthesis

et al. 2009

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Pacific salmon (Oncorhynchus spp.) disturb sediments and fertilize streams with marine-derived nutrients during their annual spawning runs, leading researchers to classify these fish as ecosystem engineers and providers of resource subsidies. While these processes strongly influence the structure and function of salmon streams, the magnitude of salmon influence varies widely across studies. Here, we use meta-analysis to evaluate potential sources of variability among studies in stream ecosystem responses to salmon. Results obtained from 37 publications that collectively included 79 streams revealed positive, but highly inconsistent, overall effects of salmon on dissolved nutrients, sediment biofilm, macroinvertebrates, resident fish, and isotopic enrichment. Variation in these response variables was commonly influenced by salmon biomass, stream discharge, sediment size, and whether studies used artificial carcass treatments or observed a natural spawning run. Dissolved nutrients were positively related to salmon biomass per unit discharge, and the slope of the relationship for natural runs was five to ten times higher than for carcass additions. Mean effects on ammonium and phosphorus were also greater for natural runs than carcass additions, an effect attributable to excretion by live salmon. In contrast, we observed larger positive effects on benthic macroinvertebrates for carcass additions than for natural runs, likely because disturbance by live salmon was absent. Furthermore, benthic macroinvertebrates and biofilm associated with small sediments (<32 mm) displayed a negative response to salmon while those associated with large sediments (>32 mm) showed a positive response. This comprehensive analysis is the first to quantitatively identify environmental and methodological variables that influence the observed effects of salmon. Identifying sources of variation in salmon-stream interactions is a critical step toward understanding why engineering and subsidy effects vary so dramatically over space and time, and toward developing management strategies that will preserve the ecological integrity of salmon streams.

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Section: Methodology Of Salmon Experiments-when Are Observations Realmentioning

confidence: 59%

Section: Methodology Of Salmon Experiments-when Are Observations Realmentioning

confidence: 99%

Pacific salmon effects on stream ecosystems: a quantitative synthesis

et al. 2009

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“…For example, .1.58 3 10 5 salmon carcasses have been placed in Oregon streams since 1995 (Compton et al 2006). Numerous experiments have placed salmon carcasses in streams and monitored the bottom-up (fertilizing) impacts of salmon carcasses on streams (e.g., Wipfli et al 1999). However, our study suggests that a stream filled with live nest-digging salmon and their eventual carcasses has much different nutrient and matter cycling, retention, and movement than a stream filled with only carcasses.…”

Section: Conservation Implicationsmentioning

confidence: 99%

Biotic Control of Stream Fluxes: Spawning Salmon Drive Nutrient and Matter Export

Moore

Schindler

Carter

et al. 2007

Ecology

130

132

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Organisms can control movements of nutrients and matter by physically modifying habitat. We examined how an ecosystem engineer, sockeye salmon (Oncorhynchus nerka), influences seasonal fluxes of sediments, nitrogen (N), and phosphorus (P) in streams of southwestern Alaska. The purpose of this study was to investigate whether salmon act as net importers or net exporters of matter and nutrients from streams and how these roles change as a function of salmon population density. We measured discharge and concentrations of suspended sediments and total N and P every 7-14 days for up to four summers in 10 streams spanning a gradient in salmon densities. We statistically allocated whole-season fluxes to salmon activities, such as excretion and bioturbation, and to export by hydrologic discharge. In addition, we used counts of spawning salmon to estimate nutrient and matter imports by salmon to streams. Large seasonal pulses of suspended sediments, P, and N were associated with salmon spawning activities, often increasing export an order of magnitude higher than during pre-salmon levels. Years and streams with more salmon had significantly higher levels of export of sediments and nutrients. In addition, years with higher precipitation had higher background export of P and N. Salmon exported an average of the equivalent of 189%, 60%, and 55% of total matter, P, and N that salmon imported in their bodies. The relative magnitude of export varied; salmon exported more than their bodies imported in 80%, 20%, and 16% across all streams and years for sediments, P, and N, respectively. A bioassay experiment indicated that the P exported by salmon is directly available for use by primary producers in the downstream lake. These results demonstrate that salmon not only move nutrients upstream on large spatial scales via their migration from the ocean and subsequent death, but also redistribute matter and nutrients on finer spatial scales through their spawning activities.

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“…nitrogen and phosphorous) (Wipfli et al, 1999). The spawning of anadromous fish delivers biological materials in the form of excretory products, gametes and carcasses that are enriched in nutrients (e.g.…”

Section: Introductionmentioning

confidence: 99%

Increases in benthic community production and metabolism in response to marine‐derived nutrients from spawning Atlantic salmon (Salmo salar)

Samways

Cunjak

2015

Freshwater Biology

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Summary Atlantic salmon (Salmo salar) and other anadromous fishes represent a major vector for transporting marine‐derived nutrients (MDNs) to Atlantic rivers. Marine‐derived nutrient subsidies may be key for maintaining ecological processes and ecosystem function in river basins. Stream channels and mesocosms designed to approximate natural river systems were used to measure the response of stream productivity in two treatments, one with marine‐derived nutrients from spawning Atlantic salmon and one without marine‐nutrient subsidies (control). Biofilm biomass (measured as chlorophyll a) and benthic metabolism (measured as the net change in dissolved oxygen) were evaluated from artificial substrata encompassing pre‐spawning, spawning and post‐spawning periods. We calculated marine‐nutrient contributions from spawning salmon using a simple empirical process model. We found that biofilm accrual was significantly greater with MDN inputs, with mesocosms having higher biomass (34.8 ± 1.2 mg chl a m−2) and growth rates (0.071 ± 0.002 mg m−2 day−1) than the stream channels (24.4 ± 4.8 mg chl a m−2 and 0.052 ± 0.003 mg m−2 day−1, respectively). Both control mesocosms and stream channels had significantly lower biomass (10.4 ± 0.7 mg chl a m−2 and 6.3 ± 2.5 mg chl a m−2, respectively) and growth rates (0.042 ± 0.008 mg m−2 day−1 and 0.029 ± 0.009 mg m−2 day−1, respectively) than treatment channels. Despite having a lower biofilm biomass, stream channels yielded a significantly greater final gross primary production of 2343.5 mg C m−2 day−1. The presence of MDNs in the stream channels shifted biofilm metabolism from heterotrophy (P/R = 0.283) to autotrophy (P/R = 2.422) within 112 days. Spawning Atlantic salmon contributed a total of 20.98 g m−2 of nitrogen and 1.04 g m−2 of phosphorous to each stream channel, through excretion and gametes alone. There was a strong predictable positive relationship between the increase in productivity and the amount of marine‐derived nitrogen and phosphorous delivered. This study highlights the importance of marine‐derived nutrients from Atlantic salmon for driving and maintaining freshwater productivity. Marine‐nutrient subsidies relieve the ‘bottom‐up’ constraints on stream productivity by facilitating the production of enough energy to support the food web, lessoning the reliance on outside energy sources.

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Influence of salmon spawner densities on stream productivity in Southeast Alaska

Cited by 52 publications

References 13 publications

Pacific salmon effects on stream ecosystems: a quantitative synthesis

Pacific salmon effects on stream ecosystems: a quantitative synthesis

Biotic Control of Stream Fluxes: Spawning Salmon Drive Nutrient and Matter Export

Increases in benthic community production and metabolism in response to marine‐derived nutrients from spawning Atlantic salmon (Salmo salar)

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