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  • Temporal and spatial variation in ecosystem metabolism and food web carbon transfer in a wet-dry tropical river

    Author(s)
    Hunt, Richard J
    Jardine, Timothy D
    Hamilton, Stephen K
    Bunn, Stuart E
    Griffith University Author(s)
    Bunn, Stuart E.
    Jardine, Timothy
    Hamilton, Stephen K.
    Year published
    2012
    Metadata
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    Abstract
    1. High light availability and stable base flow during the dry season promote primary production in perennial rivers of the wet-dry tropics, in contrast to production during the wet season which is often limited by turbidity and scouring. The Mitchell River of northern Queensland (Australia) was studied to understand controls on aquatic production and respiration in the dry season in relation to spatial and temporal gradients of light and temperature. 2. At three sites along the river, whole-ecosystem gross primary production (GPP) and respiration (ER) were measured from diel changes of dissolved oxygen using the open-channel ...
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    1. High light availability and stable base flow during the dry season promote primary production in perennial rivers of the wet-dry tropics, in contrast to production during the wet season which is often limited by turbidity and scouring. The Mitchell River of northern Queensland (Australia) was studied to understand controls on aquatic production and respiration in the dry season in relation to spatial and temporal gradients of light and temperature. 2. At three sites along the river, whole-ecosystem gross primary production (GPP) and respiration (ER) were measured from diel changes of dissolved oxygen using the open-channel single station method. Using stable carbon and nitrogen isotope analysis, aquatic consumers and their potential basal food resources were also assessed to determine food web relationships at the beginning and end of the dry season. 3. Nutrient limitation of aquatic net primary production was implied from the oligotrophic conditions and high algal C:N ratios. Rates of GPP were comparable with other tropical and temperate rivers and were regulated by light availability. 4. Respiration rates were high and similar to other tropical and subtropical rivers. Up to 52% of temporal variation of ER was explained by temperature, while P/R was lowest at the downstream site. 5. Benthic algae were the major carbon source for primary and secondary benthic consumers (insects) in the dry season but not for higher consumers (fish and crustaceans). Despite high rates of ER, which were probably supported by decaying terrestrial C3 plant material, this carbon source was not identified as contributing to animal consumer biomass. 6. While benthic algal production in the dry season sustained benthic invertebrates, the importance of external subsidies of carbon along the river, probably from the floodplain, was emphasised for fish and large invertebrates, which evidently were feeding on carbon sources not present in channel waterholes during the dry season.
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    Journal Title
    Freshwater Biology
    Volume
    57
    Issue
    3
    DOI
    https://doi.org/10.1111/j.1365-2427.2011.02708.x
    Subject
    Environmental Monitoring
    Freshwater Ecology
    Environmental Sciences
    Biological Sciences
    Publication URI
    http://hdl.handle.net/10072/49061
    Collection
    • Journal articles

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