Phytoplankton composition and constraints to biomass in the middle reaches of an Australian tropical river during base flow

Simon Townsend, M Przybylska, Michael Miloshis

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    Under high flows, the biomass of riverine phytoplankton can be constrained by short transport times and advective losses. However, under slower flows and longer transport times, secondary factors and sometimes their interaction with flow may constrain phytoplankton biomass. To contribute to a wider understanding of the riverine conditions that constrain phytoplankton biomass, we tested the hypothesis that phytoplankton of the Daly River (tropical Australia) was constrained by transport time during dry-season base flow. The river is virtually undisturbed, with oligotrophic nutrient concentrations during the dry season. The most frequently occurring taxa were planktonic, rather than benthic, and dominated by the dinoflagellate Peridinium inconspicuum which has r-strategist traits that favour rapid growth in a nutrient-deficient environment. Our hypothesis was not supported because increased downstream loads of Chlorophyll a and the domination of P. inconspicuum inferred phytoplankton net growth. Instead, phytoplankton biomass was more likely to be nutrient-limited, although transport time may limit phytoplankton growth over some reaches and for specific taxa. The present study demonstrated that even in the fast-flowing middle reaches of a river (~0.4ms -1), a population of phytoplankton can be sustained.
    Original languageEnglish
    Pages (from-to)48-59
    Number of pages12
    JournalMarine and Freshwater Research
    Volume63
    Issue number1
    DOIs
    Publication statusPublished - 2011

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    base flow
    Phytoplankton
    baseflow
    Rivers
    river flow
    Biomass
    phytoplankton
    rivers
    biomass
    Dinoflagellida
    Food
    dry season
    nutrient
    Growth
    river
    Peridinium
    nutrients
    dinoflagellate
    chlorophyll a
    nutrient content

    Cite this

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    abstract = "Under high flows, the biomass of riverine phytoplankton can be constrained by short transport times and advective losses. However, under slower flows and longer transport times, secondary factors and sometimes their interaction with flow may constrain phytoplankton biomass. To contribute to a wider understanding of the riverine conditions that constrain phytoplankton biomass, we tested the hypothesis that phytoplankton of the Daly River (tropical Australia) was constrained by transport time during dry-season base flow. The river is virtually undisturbed, with oligotrophic nutrient concentrations during the dry season. The most frequently occurring taxa were planktonic, rather than benthic, and dominated by the dinoflagellate Peridinium inconspicuum which has r-strategist traits that favour rapid growth in a nutrient-deficient environment. Our hypothesis was not supported because increased downstream loads of Chlorophyll a and the domination of P. inconspicuum inferred phytoplankton net growth. Instead, phytoplankton biomass was more likely to be nutrient-limited, although transport time may limit phytoplankton growth over some reaches and for specific taxa. The present study demonstrated that even in the fast-flowing middle reaches of a river (~0.4ms -1), a population of phytoplankton can be sustained.",
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    Phytoplankton composition and constraints to biomass in the middle reaches of an Australian tropical river during base flow. / Townsend, Simon; Przybylska, M; Miloshis, Michael.

    In: Marine and Freshwater Research, Vol. 63, No. 1, 2011, p. 48-59.

    Research output: Contribution to journalArticleResearchpeer-review

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    AU - Przybylska, M

    AU - Miloshis, Michael

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    N2 - Under high flows, the biomass of riverine phytoplankton can be constrained by short transport times and advective losses. However, under slower flows and longer transport times, secondary factors and sometimes their interaction with flow may constrain phytoplankton biomass. To contribute to a wider understanding of the riverine conditions that constrain phytoplankton biomass, we tested the hypothesis that phytoplankton of the Daly River (tropical Australia) was constrained by transport time during dry-season base flow. The river is virtually undisturbed, with oligotrophic nutrient concentrations during the dry season. The most frequently occurring taxa were planktonic, rather than benthic, and dominated by the dinoflagellate Peridinium inconspicuum which has r-strategist traits that favour rapid growth in a nutrient-deficient environment. Our hypothesis was not supported because increased downstream loads of Chlorophyll a and the domination of P. inconspicuum inferred phytoplankton net growth. Instead, phytoplankton biomass was more likely to be nutrient-limited, although transport time may limit phytoplankton growth over some reaches and for specific taxa. The present study demonstrated that even in the fast-flowing middle reaches of a river (~0.4ms -1), a population of phytoplankton can be sustained.

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