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Please use this identifier to cite or link to this item: http://hdl.handle.net/10204/1575

Title: Spatial characteristics of sediment trace metals in an eastern boundary upwelling retention area (St. Helena Bay, South Africa): A hydrodynamic-biological pump hypothesis
Authors: Monteiro, PMS
Roychoudhury, AN
Keywords: Organic carbon
Upwelling retention hydrodynamics
Sediment ecosystems
Retention Zones
St. Helena Bay - South Africa
Environmental sciences
Benguela upwelling ecosystem
Issue Date: Oct-2005
Publisher: Elsevier Science Ltd
Citation: Monteiro, PMS and Roychoudhury, AN. 2005. Spatial characteristics of sediment trace metals in an eastern boundary upwelling retention area (St. Helena Bay, South Africa): A hydrodynamic-biological pump hypothesis. Estuarine, Coastal and Shelf Science, vol 65, 2 January, pp 123-134
Abstract: St. Helena Bay, is a retention zone located in the southern Benguela upwelling system, and is an important fish nursery. However, it suffers from seasonal bottom water hypoxia causing major economic losses. Anoxic conditions are linked to sulfide fluxes from bottom sediments defined by a high sedimentation rate of organic matter. It is proposed that trace metals may play an important role in alleviating part of the ecological stress by forming sulfide complexes in such systems. A spatially intensive data set of sediment biogeochemical characteristics showed that POC (Particular organic carbon) and trace metals were accumulating in the central zone of the Bay. Furthermore, trace metal concentrations were strongly correlated with both POC and Al. To explain the observed biogeochemical relationships, a hypothesis was proposed, the hypothesis linked the upwelling retention hydrodynamics, primary productivity and sediment trace metal distribution. Trace metals are incorporated into phytoplankton cells in the euphotic zone but rapidly sediment along with particulate organics, on their senescence. Both, the biological pump and the dispersion of particulates are primarily controlled by the hydrodynamics prevalent within St. Helena Bay, which also governs the retention zone in the shadow of one of the major upwelling cells. The dynamics of entrainment-stratification drives the productivity, while a residual cyclonic gyre concentrates the surface productivity within the bay. Bed-shear stresses spatially constrain the accumulation of biogenic organic matter, which governs the trace metal biogeochemistry of the sediments, along a narrow terrigenous mud belt.
URI: http://hdl.handle.net/10204/1575
http://hdl.handle.net/10204/1575
ISSN: 0272-7714
Appears in Collections:Pollution and waste
Coastal and marine systems
General science, engineering & technology

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