Monday 22 August 2005

P6

PM0074
An investigative study into the Benguela Edge Exchange Process (BEEP)
Swart, Sebastian¹, Waldron, Howard¹ presented by I. Ansorge
1 Department Of Oceanography, University Of Cape Town, South Africa
Author email: sswart@ocean.uct.ac.za
An investigative study into the Benguela Edge Exchange Process (BEEP) is made to better understand the transfer of organic material between the continental shelf and slope. The Benguela system is seen to be an important region where this may be occurring. Data were collected on three monitoring cruises, between July and September 2004, in which particulate organic carbon (POC) and particulate nitrogen (PN) were measured to assess the presence of organic matter across the shelf/slope interface. Surface sediment data were obtained to compare continental shelf and slope organic matter concentrations. Results indicate that elevated concentrations of organic material were found near the shelf break. In some cases, POC and PN content over the shelf break reached as high as 145µg.C.l-1 and 25µg.N.l-1 respectively. Increases in ammonia concentrations of up to 2.9µmol.l-1 beyond the shelf break, is potential evidence that organic material is being deposited on the slope environments. This organic material undergoes cross-shelf transport and ends up on the continental slope regions and supports the BEEP hypothesis. Higher Corg:N ratios found in the bottom waters near the shelf edge suggests that the extent that organic matter, originating from late summer blooms, has undergone preferential degradation of nitrogen. BEEP is integral to the Joint Global Ocean Flux Study (JGOFS) and provides an understanding into the extent that slope environments act as carbon sinks.

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