Understanding the Relative Roles of Salmon Spawner Enrichment and Disturbance: A High-Frequency, Multi-Habitat Field and Modeling Approach

Organisms exert multiple, and often contrasting, influences on ecosystems. During their spawning runs, Pacific salmon (Oncorhynchus spp.) deliver nutrients to freshwater ecosystems, but also disturb benthic sediments during upstream migration and nest building. The relative importance of these contr...

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Main Authors: Janine Rüegg, Dominic T. Chaloner, Ford Ballantyne, Peter S. Levi, Chao Song, Jennifer L. Tank, Scott D. Tiegs, Gary A. Lamberti
Format: Article
Language:English
Published: Frontiers Media S.A. 2020-02-01
Series:Frontiers in Ecology and Evolution
Subjects:
Online Access:https://www.frontiersin.org/article/10.3389/fevo.2020.00019/full
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author Janine Rüegg
Dominic T. Chaloner
Ford Ballantyne
Peter S. Levi
Chao Song
Jennifer L. Tank
Scott D. Tiegs
Gary A. Lamberti
author_facet Janine Rüegg
Dominic T. Chaloner
Ford Ballantyne
Peter S. Levi
Chao Song
Jennifer L. Tank
Scott D. Tiegs
Gary A. Lamberti
author_sort Janine Rüegg
collection DOAJ
description Organisms exert multiple, and often contrasting, influences on ecosystems. During their spawning runs, Pacific salmon (Oncorhynchus spp.) deliver nutrients to freshwater ecosystems, but also disturb benthic sediments during upstream migration and nest building. The relative importance of these contrasting roles is not well understood, especially in relation to the dynamics of other environmental drivers. To assess the influence of salmon-mediated enrichment and disturbance, we measured stream biofilm metrics (production, respiration, chlorophyll a [chla], ash-free dry mass, stable isotope signatures, ∼ every 8 days) and stream variables (spawner and carcass abundance, dissolved nutrients, temperature, discharge, light, daily to every few days) from July through September (salmon arrived in August), in multiple habitats of a southeast Alaska (USA) stream. Biofilm production and biomass increased around the start of the salmon run, but declined later in the run. Biofilm stable isotope composition indicated incorporation of salmon-derived carbon and nitrogen (N) during the latter part of the run. Biofilm biomass differed among benthic habitat types (i.e., riffles, pools, stream edges) but temporal patterns were generally similar, suggesting that salmon and environmental influences were not habitat-specific. We used these high-frequency field data to parameterize an ordinary differential equation model for dissolved inorganic N, chla, and cellular N, and estimated model parameters using Markov chain Monte Carlo. Posterior distributions indicated that (1) habitats and locations were generally similar in model parameters, (2) removing the effect of salmon resulted in no change in biofilm chla early in the run (mid-August), but higher chla biomass for some habitats later in the run (September), and (3) the overall integrated salmon effect over the run was one of biofilm loss. Only by combining high frequency biofilm and environmental data with a process-based model could we determine how environmental context dynamics interact with salmon run dynamics to modulate the biofilm response in natal spawning streams.
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spelling doaj.art-77ef3dafd4154a02a1ed839ddb64761c2022-12-22T01:02:59ZengFrontiers Media S.A.Frontiers in Ecology and Evolution2296-701X2020-02-01810.3389/fevo.2020.00019495106Understanding the Relative Roles of Salmon Spawner Enrichment and Disturbance: A High-Frequency, Multi-Habitat Field and Modeling ApproachJanine Rüegg0Dominic T. Chaloner1Ford Ballantyne2Peter S. Levi3Chao Song4Jennifer L. Tank5Scott D. Tiegs6Gary A. Lamberti7Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United StatesDepartment of Biological Sciences, University of Notre Dame, Notre Dame, IN, United StatesOdum School of Ecology, University of Georgia, Athens, GA, United StatesDepartment of Biological Sciences, University of Notre Dame, Notre Dame, IN, United StatesOdum School of Ecology, University of Georgia, Athens, GA, United StatesDepartment of Biological Sciences, University of Notre Dame, Notre Dame, IN, United StatesDepartment of Biological Sciences, University of Notre Dame, Notre Dame, IN, United StatesDepartment of Biological Sciences, University of Notre Dame, Notre Dame, IN, United StatesOrganisms exert multiple, and often contrasting, influences on ecosystems. During their spawning runs, Pacific salmon (Oncorhynchus spp.) deliver nutrients to freshwater ecosystems, but also disturb benthic sediments during upstream migration and nest building. The relative importance of these contrasting roles is not well understood, especially in relation to the dynamics of other environmental drivers. To assess the influence of salmon-mediated enrichment and disturbance, we measured stream biofilm metrics (production, respiration, chlorophyll a [chla], ash-free dry mass, stable isotope signatures, ∼ every 8 days) and stream variables (spawner and carcass abundance, dissolved nutrients, temperature, discharge, light, daily to every few days) from July through September (salmon arrived in August), in multiple habitats of a southeast Alaska (USA) stream. Biofilm production and biomass increased around the start of the salmon run, but declined later in the run. Biofilm stable isotope composition indicated incorporation of salmon-derived carbon and nitrogen (N) during the latter part of the run. Biofilm biomass differed among benthic habitat types (i.e., riffles, pools, stream edges) but temporal patterns were generally similar, suggesting that salmon and environmental influences were not habitat-specific. We used these high-frequency field data to parameterize an ordinary differential equation model for dissolved inorganic N, chla, and cellular N, and estimated model parameters using Markov chain Monte Carlo. Posterior distributions indicated that (1) habitats and locations were generally similar in model parameters, (2) removing the effect of salmon resulted in no change in biofilm chla early in the run (mid-August), but higher chla biomass for some habitats later in the run (September), and (3) the overall integrated salmon effect over the run was one of biofilm loss. Only by combining high frequency biofilm and environmental data with a process-based model could we determine how environmental context dynamics interact with salmon run dynamics to modulate the biofilm response in natal spawning streams.https://www.frontiersin.org/article/10.3389/fevo.2020.00019/fullmarine-derived nutrientsepilithonperiphytonenvironmental contextsalmon runsOncorhynchus
spellingShingle Janine Rüegg
Dominic T. Chaloner
Ford Ballantyne
Peter S. Levi
Chao Song
Jennifer L. Tank
Scott D. Tiegs
Gary A. Lamberti
Understanding the Relative Roles of Salmon Spawner Enrichment and Disturbance: A High-Frequency, Multi-Habitat Field and Modeling Approach
Frontiers in Ecology and Evolution
marine-derived nutrients
epilithon
periphyton
environmental context
salmon runs
Oncorhynchus
title Understanding the Relative Roles of Salmon Spawner Enrichment and Disturbance: A High-Frequency, Multi-Habitat Field and Modeling Approach
title_full Understanding the Relative Roles of Salmon Spawner Enrichment and Disturbance: A High-Frequency, Multi-Habitat Field and Modeling Approach
title_fullStr Understanding the Relative Roles of Salmon Spawner Enrichment and Disturbance: A High-Frequency, Multi-Habitat Field and Modeling Approach
title_full_unstemmed Understanding the Relative Roles of Salmon Spawner Enrichment and Disturbance: A High-Frequency, Multi-Habitat Field and Modeling Approach
title_short Understanding the Relative Roles of Salmon Spawner Enrichment and Disturbance: A High-Frequency, Multi-Habitat Field and Modeling Approach
title_sort understanding the relative roles of salmon spawner enrichment and disturbance a high frequency multi habitat field and modeling approach
topic marine-derived nutrients
epilithon
periphyton
environmental context
salmon runs
Oncorhynchus
url https://www.frontiersin.org/article/10.3389/fevo.2020.00019/full
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