Nitrogen loads explain primary productivity in estuaries at the ecosystem scale

Ryan Woodland, Jim THOMSON, Ralph MAC NALLY, Paul Reich, V Evrard, Fiona Wary, Jeffrey Walker, Perran Cook

    Research output: Contribution to journalArticle

    11 Citations (Scopus)

    Abstract

    Increased nutrient loads stimulate estuary primary productivity and can alter the structure and function of biological communities within estuaries, particularly when producer groups respond differently to changes in nutrient availability. Here, the relative influence of riverine inputs of nitrogen and phosphorus were compared to determine their contribution to estuarine primary producers at large spatial scales. Indices of demersal (extent of macroalgae relative to other vegetation, total shallow water area vegetated) and planktonic (seasonally averaged chlorophyll concentration) primary producer communities were derived at whole-of-ecosystem scales in 14 estuaries dispersed across a longitudinal gradient using aerial imaging, underwater videography and in situ monitoring. A model selection framework was used to relate annual nutrient loads (total nitrogen [TN], dissolved inorganic nitrogen [DIN], total phosphorus [TP]), sediment loads (TSS), molar stoichiometric load ratios (TNM: TPM), and estuary water residence times to the demersal and planktonic indices. Dissolved inorganic nitrogen was the best predictor of the extent of macroalgae, total vegetation coverage, and the concentration of planktonic chlorophyll. Rapid increases in all three indices occurred at inorganic nitrogen loads of ~ 5-10 Mg km-2 yr-1. There was some evidence that TNM: TPM, TP and TSS loads were informative model covariates. Relative to DIN loads, TP loads were a poor predictor of the macroalgal and planktonic indices. These findings underscore the critical role of catchment-derived nitrogen in contributing to producer communities at the whole-of-ecosystem scale and support the growing consensus that nitrogen loads (in addition to phosphorus) must be managed to effectively alleviate eutrophication in estuaries.
    Original languageEnglish
    Pages (from-to)1751-1762
    Number of pages12
    JournalLimnology and Oceanography
    Volume60
    Issue number5
    DOIs
    Publication statusPublished - 2015

    Fingerprint

    primary productivity
    estuaries
    estuary
    dissolved inorganic nitrogen
    phosphorus
    productivity
    ecosystems
    ecosystem
    nitrogen
    pollution load
    macroalgae
    chlorophyll
    videography
    longitudinal gradient
    vegetation
    nutrient
    inorganic nitrogen
    nutrient availability
    eutrophication
    residence time

    Cite this

    Woodland, R., THOMSON, J., MAC NALLY, R., Reich, P., Evrard, V., Wary, F., ... Cook, P. (2015). Nitrogen loads explain primary productivity in estuaries at the ecosystem scale. Limnology and Oceanography, 60(5), 1751-1762. https://doi.org/10.1002/lno.10136
    Woodland, Ryan ; THOMSON, Jim ; MAC NALLY, Ralph ; Reich, Paul ; Evrard, V ; Wary, Fiona ; Walker, Jeffrey ; Cook, Perran. / Nitrogen loads explain primary productivity in estuaries at the ecosystem scale. In: Limnology and Oceanography. 2015 ; Vol. 60, No. 5. pp. 1751-1762.
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    abstract = "Increased nutrient loads stimulate estuary primary productivity and can alter the structure and function of biological communities within estuaries, particularly when producer groups respond differently to changes in nutrient availability. Here, the relative influence of riverine inputs of nitrogen and phosphorus were compared to determine their contribution to estuarine primary producers at large spatial scales. Indices of demersal (extent of macroalgae relative to other vegetation, total shallow water area vegetated) and planktonic (seasonally averaged chlorophyll concentration) primary producer communities were derived at whole-of-ecosystem scales in 14 estuaries dispersed across a longitudinal gradient using aerial imaging, underwater videography and in situ monitoring. A model selection framework was used to relate annual nutrient loads (total nitrogen [TN], dissolved inorganic nitrogen [DIN], total phosphorus [TP]), sediment loads (TSS), molar stoichiometric load ratios (TNM: TPM), and estuary water residence times to the demersal and planktonic indices. Dissolved inorganic nitrogen was the best predictor of the extent of macroalgae, total vegetation coverage, and the concentration of planktonic chlorophyll. Rapid increases in all three indices occurred at inorganic nitrogen loads of ~ 5-10 Mg km-2 yr-1. There was some evidence that TNM: TPM, TP and TSS loads were informative model covariates. Relative to DIN loads, TP loads were a poor predictor of the macroalgal and planktonic indices. These findings underscore the critical role of catchment-derived nitrogen in contributing to producer communities at the whole-of-ecosystem scale and support the growing consensus that nitrogen loads (in addition to phosphorus) must be managed to effectively alleviate eutrophication in estuaries.",
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    Woodland, R, THOMSON, J, MAC NALLY, R, Reich, P, Evrard, V, Wary, F, Walker, J & Cook, P 2015, 'Nitrogen loads explain primary productivity in estuaries at the ecosystem scale', Limnology and Oceanography, vol. 60, no. 5, pp. 1751-1762. https://doi.org/10.1002/lno.10136

    Nitrogen loads explain primary productivity in estuaries at the ecosystem scale. / Woodland, Ryan; THOMSON, Jim; MAC NALLY, Ralph; Reich, Paul; Evrard, V; Wary, Fiona; Walker, Jeffrey; Cook, Perran.

    In: Limnology and Oceanography, Vol. 60, No. 5, 2015, p. 1751-1762.

    Research output: Contribution to journalArticle

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    T1 - Nitrogen loads explain primary productivity in estuaries at the ecosystem scale

    AU - Woodland, Ryan

    AU - THOMSON, Jim

    AU - MAC NALLY, Ralph

    AU - Reich, Paul

    AU - Evrard, V

    AU - Wary, Fiona

    AU - Walker, Jeffrey

    AU - Cook, Perran

    PY - 2015

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    N2 - Increased nutrient loads stimulate estuary primary productivity and can alter the structure and function of biological communities within estuaries, particularly when producer groups respond differently to changes in nutrient availability. Here, the relative influence of riverine inputs of nitrogen and phosphorus were compared to determine their contribution to estuarine primary producers at large spatial scales. Indices of demersal (extent of macroalgae relative to other vegetation, total shallow water area vegetated) and planktonic (seasonally averaged chlorophyll concentration) primary producer communities were derived at whole-of-ecosystem scales in 14 estuaries dispersed across a longitudinal gradient using aerial imaging, underwater videography and in situ monitoring. A model selection framework was used to relate annual nutrient loads (total nitrogen [TN], dissolved inorganic nitrogen [DIN], total phosphorus [TP]), sediment loads (TSS), molar stoichiometric load ratios (TNM: TPM), and estuary water residence times to the demersal and planktonic indices. Dissolved inorganic nitrogen was the best predictor of the extent of macroalgae, total vegetation coverage, and the concentration of planktonic chlorophyll. Rapid increases in all three indices occurred at inorganic nitrogen loads of ~ 5-10 Mg km-2 yr-1. There was some evidence that TNM: TPM, TP and TSS loads were informative model covariates. Relative to DIN loads, TP loads were a poor predictor of the macroalgal and planktonic indices. These findings underscore the critical role of catchment-derived nitrogen in contributing to producer communities at the whole-of-ecosystem scale and support the growing consensus that nitrogen loads (in addition to phosphorus) must be managed to effectively alleviate eutrophication in estuaries.

    AB - Increased nutrient loads stimulate estuary primary productivity and can alter the structure and function of biological communities within estuaries, particularly when producer groups respond differently to changes in nutrient availability. Here, the relative influence of riverine inputs of nitrogen and phosphorus were compared to determine their contribution to estuarine primary producers at large spatial scales. Indices of demersal (extent of macroalgae relative to other vegetation, total shallow water area vegetated) and planktonic (seasonally averaged chlorophyll concentration) primary producer communities were derived at whole-of-ecosystem scales in 14 estuaries dispersed across a longitudinal gradient using aerial imaging, underwater videography and in situ monitoring. A model selection framework was used to relate annual nutrient loads (total nitrogen [TN], dissolved inorganic nitrogen [DIN], total phosphorus [TP]), sediment loads (TSS), molar stoichiometric load ratios (TNM: TPM), and estuary water residence times to the demersal and planktonic indices. Dissolved inorganic nitrogen was the best predictor of the extent of macroalgae, total vegetation coverage, and the concentration of planktonic chlorophyll. Rapid increases in all three indices occurred at inorganic nitrogen loads of ~ 5-10 Mg km-2 yr-1. There was some evidence that TNM: TPM, TP and TSS loads were informative model covariates. Relative to DIN loads, TP loads were a poor predictor of the macroalgal and planktonic indices. These findings underscore the critical role of catchment-derived nitrogen in contributing to producer communities at the whole-of-ecosystem scale and support the growing consensus that nitrogen loads (in addition to phosphorus) must be managed to effectively alleviate eutrophication in estuaries.

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    DO - 10.1002/lno.10136

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