Nature 274, 678 - 680 (17 August 1978); doi:10.1038/274678a0

Very low salinity regions of estuaries: important sites for chemical and biological reactions

A. W. MORRIS, R. F. C. MANTOURA, A. J. BALE & R. J. M. HOWLAND

Institute for Marine Environmental Research, Prospect Place, The Hoe, Plymouth, UK

THE importance of biogeochemical interactions in estuaries is widely recognised^1,2,4−6; in particular, theoretical models of estuarine speciation of trace metals⁷ and of the pH−carbonate system⁸ predict that sharp changes of thermodynamic equilibrium conditions should occur at very low salinities (<1). However, because of the limitations of conventional sampling strategies¹², the chemical properties of this freshwater−seawater interphase (FSI) have not been adequately characterised. Instead, the expected variability has usually been represented by a scatter of spatially and temporally unresolved data points^1,3,5,6. Over the past two years, we have carried out periodic detailed investigations of the immediate mixing of the fresh and brackish water in the Tamar Estuary, South West England and we present data here for 11 determinands which point to the FSI as being an important site for chemical and biological processes in estuaries.

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