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SFS Annual Meeting

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Freshwater systems are considered particularly vulnerable to human impact, through changes to water regimes and quality, invasion by exotic species and climate change. We investigated the growth responses of two invasive exotic (Egeria densa and Salvinia molesta) and one native (Vallisneria spiralis) species to additional low nitrogen (NO3-N) concentrations. Egeria densa and V. spiralis produced more biomass under higher nitrate concentrations but S. molesta biomass production was greatest at the mid-range nitrate concentrations (0.05 – 0.1 mg NO3-NL-1). In a second experiment, we compared growth responses of two native species (Azolla filliculoides and Vallisneria spiralis) and the exotic Salvinia molesta at ambient and elevated CO2 concentrations. Biomass production of the native A. filiculoides was significantly higher under elevated CO2 whereas its specific leaf area (SLA) was lower under elevated CO2 concentration. Biomass production and growth traits of the invasive exotic S. molesta and the native V. spiralis were unaffected by elevated CO2. We conclude that exotic species are now an important component of Australia’s freshwater systems and that human impact, through eutrophication and climate change, is likely to further facilitate some exotic plant species in these ecosystems.

Guyo Gufu (Primary Presenter/Author), Macquarie University,;