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| Titel |
Phosphate removal in oxygen minimum zones off Africa |
| VerfasserIn |
Sarah Sokoll, Timothy G. Ferdelman, Moritz Holtappels, Tobias Goldhammer, Marcel M. M. Kuypers |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080739
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| Zusammenfassung |
| The flux of limiting nutrients (N, P, Si and Fe) to the surface ocean controls phytoplankton
growth and species composition. Shelf and margin sediments release considerable amounts of
nutrients into the bottom water from which they are eventually transported to surface waters.
However not well understood is how the flux of phosphate (P) across the benthic boundary
layer (BBL) is controlled by geochemical and biologically mediated processes such as redox
reaction, chelation, particle formation, sorption and desorption to organic and inorganic
particles. P transformation between the dissolved and the particulate phase significantly
influences the P distribution in the water column and, for example, might lead to the
significant P accumulation observed for anoxic bottom waters of the oxygen minimum
zone (OMZ) off Namibia. To investigate P accumulation on particles in the water
column under oxic and anoxic conditions we conducted isotope labeling experiments
during two cruises in 2011 to the OMZs of Mauritania and Namibia. We applied
radioactive tracer (33PO43) incubations, sequential P extraction and nanoSIMS
analyses to measure particulate P formation rates and to discriminate between biotic
and abiotic accumulation. Under oxic conditions, formation rates of particulate P
ranged between 3.1 and 29.7 nmol P L-1 d-1 and increased in the BBL towards the
seafloor. Sequential P extraction revealed that 34-67% of phosphate was taken up into
biomass. Calculated cellular uptake rates of ~0.24 to 29 x 10-18 mol cell-1 d-1 were
significantly above those calculated from oxygen consumption and Redfield ratio
suggesting intracellular P storage. In contrast, in near anoxic bottom waters ( |
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