Verification of a conceptual model of water quality for small temporarily open/closed estuaries: East Kleinemonde Estuary, South Africa
Susan Taljaard A C , Gavin Snow B , Phumelele Gama B and Lara van Niekerk A
+ Author Affiliations
- Author Affiliations
A CSIR, Natural Resources and the Environment, PO Box 320, Stellenbosch, 7599, South Africa.
B Botany Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth, 6031, South Africa.
C Corresponding author. Email: staljaar@csir.co.za
Marine and Freshwater Research 60(3) 234-245 https://doi.org/10.1071/MF07226
Submitted: 28 November 2007 Accepted: 24 October 2008 Published: 27 March 2009
Abstract
The dynamics of the world’s larger permanently open estuaries have been well documented, but much less is known about the complex dynamics of smaller temporarily open/closed estuaries (TOCEs). Seventy per cent of South Africa’s 250 estuaries are classified as TOCEs, and many are less than 50 ha. A conceptual model of the water-quality dynamics of TOCEs has been proposed, primarily considering three hydrodynamic states (closed, semi-closed and open). This paper uses data from the East Kleinemonde Estuary, a small TOCE in the warm-temperate region of South Africa, to verify the model, focusing on physico-chemical parameters (salinity, temperature, pH, dissolved oxygen and turbidity) and inorganic macronutrients (dissolved inorganic nitrogen and dissolved inorganic phosphate) for the open and closed states. The results generally fitted the model in terms of the behaviour of the physico-chemical parameters and macronutrients in the water column. This knowledge provides a first approach to predict the water-quality dynamics in small TOCEs, thereby ensuring that the often limited resources are targeted at resolving uncertainties at appropriate temporal and spatial scales. TOCEs are not unique to South Africa and also occur along other coasts (Mediterranean and south-western Australia) where this type of model could also be applied.
Additional keywords: nutrients, physico-chemical parameters.
Acknowledgements
The authors would like to thank Bernard Mackenzie for his valuable contribution through the collection of the weekly physico-chemical data sets over the study period, Dr Paul Cowley for sharing the data on mouth observations and providing insight into the functioning of this estuary, the Water Research Commission (South Africa) for funding this project and the anonymous reviewers.
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