Internal nutrient flux in an inland water supply reservoir, New South Wales, Australia
Nutrient dynamics at the water–sediment interface in the Suma Park Reservoir, Australia, was assessed under simulated laboratory conditions using intact sediment cores. This laboratory experiment demonstrated that the nutrient influx between the sediment and the water column, in both oxic and anoxic environments, contributed substantially to the total nutrient budget and overall recycling of the biologically available nutrients in the reservoir. This study also confirmed that the bottom sediments act as a source of ammonium-nitrogen (NH4-N) and filterable reactive phosphorus (FRP), but function as a sink for nitrate-nitrogen (NO3-N). Extrapolation of the experiment data revealed that the highest nutrient flux was obtained under a summer-anoxic incubation, with the internal loads of FRP and NH4-N accounting for ≈ 365% and 338% of their external annual loads, respectively. The internal loss of NO3-N from the summer anoxic incubation was ≈ 7% of its external annual load. The temperature and dissolved oxygen concentration were the most important factors influencing the nutrient flux and internal loading. Denitrification was believed to be an eminent route of nitrate loss from the reservoir.