Diurnal variations in the chemical environment of a shallow tidal inlet, Gulf St Vincent, South Australia: Implications for water quality and trace metal migration

Abstract

During ‘dodge’ tide phases in South Australian Gulf waters, there is negligible movement of water overlying the sediments of sheltered tidal inlets for up to 24 h, and extreme fluctuations in redox potential, pH, dissolved oxygen and H 2S levels occur. During normal tidal phases, water ebbing from the tidal flats early in the morning has a lower pH, redox potential and dissolved oxygen content than inflowing sea water, and sometimes a high content of H 2S. Variations in dissolved metals, carbonate alkalinity and dissolved organic carbon have also been recorded. Field and laboratory observations demonstrate the dominant influence of solar irradiance on these parameters, and also the importance of water residence time, sediment characteristics and the density of benthic organisms. Implications for water quality, metal enrichment and the release of trace metals and nutrients from sediments are proposed for Barker Inlet, where waste water discharges into a shallow, sheltered environment.