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  • Effects of water level fluctuations on nitrogen dynamics in littoral macrophytes

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    Author(s)
    Lu, Jing
    Bunn, Stuart
    Burford, Michele
    Griffith University Author(s)
    Bunn, Stuart E.
    Burford, Michele A.
    Lu, Jing
    Year published
    2018
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    Abstract
    Sustained water level drawdown followed by rewetting has the potential to shift macrophytes from a nutrient sink to a source, but the fate of macrophyte-derived nutrients after rewetting is not well understood. We investigated the fate of released nitrogen (N) from isotopically labeled macrophyte litter over a 4-week period after rewetting. We used three treatments: (1) different species in the litter (invasive Cabomba caroliniana vs. native Hydrilla verticillata); (2) sediment desiccation history (“dried then rewetted” vs. “constantly wet”); (3) living macrophytes (presence vs. absence). Our results showed that the Cabomba ...
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    Sustained water level drawdown followed by rewetting has the potential to shift macrophytes from a nutrient sink to a source, but the fate of macrophyte-derived nutrients after rewetting is not well understood. We investigated the fate of released nitrogen (N) from isotopically labeled macrophyte litter over a 4-week period after rewetting. We used three treatments: (1) different species in the litter (invasive Cabomba caroliniana vs. native Hydrilla verticillata); (2) sediment desiccation history (“dried then rewetted” vs. “constantly wet”); (3) living macrophytes (presence vs. absence). Our results showed that the Cabomba litter treatment had a significantly higher percentage of macrophyte-derived 15N in the dissolved fraction of the water column and assimilated by phytoplankton (higher chlorophyll a concentrations), compared to the Hydrilla litter. The treatments with sediment desiccation also had a significantly higher percentage of 15N in the dissolved fraction and used by phytoplankton after rewetting, but less in the sediment, compared to the constantly wet treatment. The presence of living macrophytes partially reduced the 15N increase in the water column and/or sediment, but the scale of the effect was species- and biomass-dependent. Our study showed that sediment pre-desiccation changed the fate of macrophyte-derived 15N after rewetting, increasing the impact on water quality. This was further exacerbated by the presence of litter from an invasive species. This study highlights the need to manage water levels to maintain healthy macrophyte beds and thereby addressing water quality issues in lakes and reservoirs.
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    Journal Title
    Limnology and Oceanography
    DOI
    https://doi.org/10.1002/lno.10673
    Copyright Statement
    © 2017 The Authors & Limnology and Oceanography published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
    Note
    This publication has been entered into Griffith Research Online as an Advanced Online Version.
    Subject
    Earth sciences
    Chemical oceanography
    Environmental sciences
    Environmental management
    Biological sciences
    Publication URI
    http://hdl.handle.net/10072/370882
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    • Journal articles

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