Tidally driven pore water exchange in offshore intertidal sandbanks: Part I. Field measurements

Gibbes, B., Robinson, C., Carey, H., Li, L. and Lockington, D. (2008) Tidally driven pore water exchange in offshore intertidal sandbanks: Part I. Field measurements. Estuarine, Coastal and Shelf Science, 79 1: 121-132. doi:10.1016/j.ecss.2008.03.021

Author Gibbes, B.
Robinson, C.
Carey, H.
Li, L.
Lockington, D.
Title Tidally driven pore water exchange in offshore intertidal sandbanks: Part I. Field measurements
Journal name Estuarine, Coastal and Shelf Science   Check publisher's open access policy
ISSN 0272-7714
Publication date 2008-08-10
Sub-type Article (original research)
DOI 10.1016/j.ecss.2008.03.021
Volume 79
Issue 1
Start page 121
End page 132
Total pages 12
Editor D. S. McClusky
E. Wolanski
I. Valiela
Place of publication London, U.K
Publisher Academic Press
Collection year 2009
Language eng
Subject C1
960903 Coastal and Estuarine Water Management
090509 Water Resources Engineering
Formatted abstract
In recent years blooms of the toxic marine cyanobacteria Lyngbya majuscula have been frequently observed in a system of offshore intertidal sandbanks in Moreton Bay, Australia. Past research suggests that these blooms are linked to the presence of bio-available forms of iron. Using hydraulic and pore water chemistry data collected from a shore normal transect at an offshore bloom site, the role of tidally driven exchange as a potential mechanism for delivery of bio-available iron across the sediment–water interface was examined. Field data revealed a residual pore water flow system in the sandbank, with seawater entering the upper sandbank platform and discharging through the bank edge. Upward flow and elevated near-surface dissolved Fe(II) concentrations (>20 μM Fe(II) at −0.05 m depth) were measured simultaneously in the discharge zones at the sandbank edge. The measured concentrations were more than four times greater than concentrations previously shown to stimulate L. majuscula growth. These results suggest that the tidally driven exchange mechanism might be capable of delivering dissolved Fe(II) to sites within offshore intertidal sandbanks where blooms of L. majuscula have been observed. While the source of the iron was not identified, potential candidates are discussed. These findings have implications for the current conceptual model for L. majuscula blooms in offshore intertidal sandbanks within Moreton Bay. Further investigations are required to fully understand the role of tidally driven exchange in controlling the export of bio-available iron to coastal waters at the field site. In particular there is a need to better assess the link between the pore water flows and the geochemical reactions that might occur along the flow path.
© 2008 Elsevier Ltd. All rights reserved.
Keyword Pore water exchange
Lyngbya majuscula
Algal blooms
Offshore sandbank
Moreton Bay, Australia
Q-Index Code C1
Q-Index Status Confirmed Code

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Created: Fri, 27 Mar 2009, 12:05:00 EST by Katherine Montagu on behalf of School of Civil Engineering