Evidence that increased nitrogen efflux from wave-influenced marine sediment enhances pelagic phytoplankton production on the inner continental shelf of Western Australia
Jim GreenwoodA CSIRO Marine and Atmospheric Research, Underwood Avenue, Floreat, WA 6014, Australia.
B Email: jim.greenwood@csiro.au
Marine and Freshwater Research 61(5) 625-632 https://doi.org/10.1071/MF09236
Submitted: 21 September 2009 Accepted: 12 November 2009 Published: 28 May 2010
Abstract
Increased biological and chemical reaction rates within permeable continental-shelf sediment can result from the action of passing surface waves, especially when the seabed is rippled. The effect of this on the exchange of nitrogen between the sediment and water column is the focus of the present paper. The continental shelf of Western Australia is used as an example. A time series of chlorophyll a is compared with surface-wave height revealing seasonal and sub-seasonal correlation between the two variables. At the same time, results from a coupled pelagic–benthic biogeochemical model show that temperature-controlled changes in sedimentary nitrogen efflux cannot account for the observed seasonal changes in chlorophyll a in the overlying water column. It is proposed that enhanced pore-water circulation within the sediment, caused by the action of passing surface waves, results in an increase in the efflux of nitrogen from the sediment during winter, supporting higher pelagic phytoplankton production. The parameterisation of sedimentary nitrogen mineralisation as a function of the square of wave height is suggested for the inclusion of this effect in regional-scale continental shelf models.
Additional keywords: modelling, phytoplankton, sediment, waves.
Acknowledgements
This work was supported by the West Australian Marine Science Institute and the Australian Government Wealth from Oceans Flagship. Wave buoy data was obtained from the Department of Planning and Infrastructure, Western Australian Government.
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