Short Communication

Evidence of carbon transport between shelf and slope waters in the Benguela upwelling system

  • S Swart Department of Oceanography, University of Cape Town, Rondebosch 7700, South Africa
  • HN Waldron Department of Oceanography, University of Cape Town, Rondebosch 7700, South Africa
  • L Hutchings Marine and Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa

Abstract

The world ocean is pivotal in the global carbon cycle and, subsequent to anthropogenic loading of the atmosphere with CO2, its ability to sequestrate photosynthetically-fixed carbon is important with respect to our ability to predict climate change. A study of the Benguela Edge Exchange Processes was carried out to better understand the transfer of organic material between the continental shelf and slope environments in the southern Benguela upwelling system off the south-western coast of South Africa. Data were collected during three hydrographic surveys in which particulate organic carbon (POC) and nitrogen (PON) were measured to assess the distribution of organic matter across the shelf–slope interface. Results indicate that significant concentrations of organic material (POC > 80μg l–1 and PON > 13μg l–1) were found near the shelf break, providing evidence that shelf-derived primary production may be transported into deep waters offshore and sequestrated in the long-term. The findings of the survey data are supported by a carbon budget calculation. This study contributes to the Joint Global Ocean Flux Study and to an understanding of the extent to which slope environments act as carbon sinks.

Keywords: cross-shelf transport; organic carbon; southern Benguela

African Journal of Marine Science 2007, 29(1): 137–139
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X