Sediment–seawater solute flux in a polluted New Zealand estuary

Vopel, Kay; Wilson, Peter S.; Zeldis, John

Sediment–seawater solute flux in a polluted New Zealand estuary

2012

Vopel, Kay | Wilson, Peter S. | Zeldis, John

We investigated the sediment–seawater solute flux at five sites in the polluted Avon–Heathcote Estuary, New Zealand, to provide a point of comparison for future studies of the effects of the closure of a major wastewater outfall into the estuary. Sediments collected in winters 2007 and 2008, and summer 2008, ranked consistently in organic matter content. Microelectrode profiling and sediment-core incubations revealed (1) a dominant role of microphytes in regulating solute flux causing significant differences in the dark and light sediment O₂ consumption (Rd, Rₗ), total sediment O₂ utilisation (TOUd, TOUₗ), and inorganic nutrient flux, (2) consistent ranking of sites in solute flux, and (3) a clear solute-flux signature of the wastewater effluent. Sediment near the wastewater outfall exhibited the highest absolute R and TOU, the lowest ratio Rₗ/Rd, the highest dark efflux of dissolved reactive phosphorus and ammonium, and the highest dark and light uptake of nitrate+nitrite.

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