Solid phase phosphorus geochemistry in surface sediments of sediment cores GeoB3718-4, GeoB3702-2 and GeoB3707-4
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| Natura: | Dataset Open Access |
| Lingua: | en |
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PANGAEA
2010
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| _version_ | 1867167662834974720 |
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| author | Küster-Heins, Kathrin Steinmetz, Ekkehard de Lange, Gert J Zabel, Matthias |
| author_facet | Küster-Heins, Kathrin Steinmetz, Ekkehard de Lange, Gert J Zabel, Matthias |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | In this study we investigate benthic phosphorus cycling in recent continental margin sediments at three sites off the Namibian coastal upwelling area. Examination of the sediments reveals that organic and biogenic phosphorus are the major P-containing phases preserved. High Corg/Porg ratios just at the sediment surface suggest that the preferential regeneration of phosphorus relative to that of organic carbon has either already occurred on the suspension load or that the organic matter deposited at these sites is already rather refractory. Release of phosphate in the course of benthic microbial organic matter degradation cannot be identified as the dominating process within the observed internal benthic phosphorus cycle. Dissolved phosphate and iron in the pore water are closely coupled, showing high concentrations below the oxygenated surface layer of the sediments and low concentrations at the sediment-water interface. The abundant presence of Fe(III)-bound phosphorus in the sediments document the co-precipitation of both constituents as P-containing iron (oxyhydr)oxides. However, highly dissolved phosphate concentrations in pore waters cannot be explained, neither by simple mass balance calculations nor by the application of an established computer model. Under the assumption of steady state conditions, phosphate release rates are too high as to be balanced with a solid phase reservoir. This discrepancy points to an apparent lack of solid phase phosphorus at sediment depth were suboxic conditions prevail. We assume that the known, active, fast and episodic particle mixing by burrowing macrobenthic organisms could repeatedly provide the microbially catalyzed processes of iron reduction with authigenic iron (oxyhydro)oxides from the oxic surface sediments. Accordingly, a multiple internal cycling of phosphate and iron would result before both elements are buried below the iron reduction zone. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_736461 |
| institution | PANGAEA |
| language | en |
| publishDate | 2010 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Solid phase phosphorus geochemistry in surface sediments of sediment cores GeoB3718-4, GeoB3702-2 and GeoB3707-4 Küster-Heins, Kathrin Steinmetz, Ekkehard de Lange, Gert J Zabel, Matthias Center for Marine Environmental Sciences; GeoB3702-2; GeoB3707-4; GeoB3718-4; M34/2; MARUM; Meteor (1986); MUC; MultiCorer; Northern Cape Basin In this study we investigate benthic phosphorus cycling in recent continental margin sediments at three sites off the Namibian coastal upwelling area. Examination of the sediments reveals that organic and biogenic phosphorus are the major P-containing phases preserved. High Corg/Porg ratios just at the sediment surface suggest that the preferential regeneration of phosphorus relative to that of organic carbon has either already occurred on the suspension load or that the organic matter deposited at these sites is already rather refractory. Release of phosphate in the course of benthic microbial organic matter degradation cannot be identified as the dominating process within the observed internal benthic phosphorus cycle. Dissolved phosphate and iron in the pore water are closely coupled, showing high concentrations below the oxygenated surface layer of the sediments and low concentrations at the sediment-water interface. The abundant presence of Fe(III)-bound phosphorus in the sediments document the co-precipitation of both constituents as P-containing iron (oxyhydr)oxides. However, highly dissolved phosphate concentrations in pore waters cannot be explained, neither by simple mass balance calculations nor by the application of an established computer model. Under the assumption of steady state conditions, phosphate release rates are too high as to be balanced with a solid phase reservoir. This discrepancy points to an apparent lack of solid phase phosphorus at sediment depth were suboxic conditions prevail. We assume that the known, active, fast and episodic particle mixing by burrowing macrobenthic organisms could repeatedly provide the microbially catalyzed processes of iron reduction with authigenic iron (oxyhydro)oxides from the oxic surface sediments. Accordingly, a multiple internal cycling of phosphate and iron would result before both elements are buried below the iron reduction zone. |
| title | Solid phase phosphorus geochemistry in surface sediments of sediment cores GeoB3718-4, GeoB3702-2 and GeoB3707-4 |
| topic | Center for Marine Environmental Sciences; GeoB3702-2; GeoB3707-4; GeoB3718-4; M34/2; MARUM; Meteor (1986); MUC; MultiCorer; Northern Cape Basin |
| url | https://doi.org/10.1594/PANGAEA.736461 |