Shelf Sea Biogeochemistry blog

Monday, 9 March 2015

Moving sediments at the bottom of the ocean

On Monday we got to see another sediment re-suspension experiment carried out by Charlie Thompson of the University of Southampton (UoS), and Sarah Reynolds of Portsmouth University. 

Charlie Thompson (UoS) has written the following about this experiment which was carried out using a piece of equipment called a benthic flume:
The seabed isn’t solid, but is instead made of mobile sediments (muds, sands and gravels), which are moved around by the action of waves and tides. Charlie and Sarah’s work looks at what happens to nutrients, carbon and the sediments themselves when they begin to be re-suspended and moved around by the tides and water currents.


Benthic flume sitting on the deck
 One way to do this is using a benthic flume (see photo above , which sits on the seabed and uses a motor driven paddle system to allow us to recreate strong currents onto the actual sediment at the bottom of the ocean, when and where we want them. By doing this, we are able to measure when a specific type of sediment (e.g. Sand or mud) starts to move – which in turn allows us to predict how often that sediment might be re-suspended by natural water flows over the seabed. We can also determine how the fluxes of nutrients and carbon into or out of the bed are changed compared to on a stationary bed from water samples taken at time intervals during the experiments.


Benthic flume being deployed over the side of the RRS Discovery


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