Holmkvist,L., Arning,E.T., Kuster(uの頭に¨)-Heins,K., Vandieken,V., Peckmann,J., Zabel,M. and Jorgensen(oに/が付く),B.B.(2010): Phosphate geochemistry, mineralization processes, and Thioploca distribution in shelf sediments off central Chile. Marine Geology, 277, 61-72.

『チリ中央部沖の棚堆積物におけるリン酸塩の地球化学的性質と鉱化過程とバクテリアのチオプロカの分布』


Abstract
 Sediments underlying the major coastal upwelling systems of the world oceans are hot-spots of modern formation of hydroxyapatites, often associated with benthic communities of large, nitrate-accumulating sulfur bacteria. We studied the association between phosphate release, organic phosphorus mineralization, and occurrence of dense communities of the filamentous sulfur bacteria, Thioploca spp., on the continental shelf off central Chile during the austral summer when high phytoplankton productivity and anoxic bottom water prevailed. Freshly deposited phytodetritus stimulated extremely high sulfate reduction rates, which supported a large Thioploca community of up to 100 g biomass per m2. Effective bacterial sulfide uptake kept the sulfide concentration low, which enabled the accumulation of free iron, thus demonstrating intensive iron reduction concurrent with sulfate reduction. Phosphate released to the pore water reached 100-300 μM peak concentrations within the uppermost 0-5 cm and phosphate was lost to the overlying anoxic water column. The large phosphate release was not directly related to the presence of Thioploca but was rather the result of a high deposition and mineralization rate of fresh organic detritus. Although the pore water was super-saturated with respect to hydroxyapatite, this mineral was only a minor P-component in the sediment. Most solid-phase phosphate was bound to iron.

Keywords: Chile; Thioploca; Phosphorus; Hydroxyapatite; Phosphate release』

1. Introduction
2. Materials and methods
 2.1. Sampling
 2.2. Pore water extraction and solid phase sampling
 2.3. Pore water analysis
 2.4. Solid phase iron and sulfur extraction
 2.5. Sequential solid phase phosphate extraction
 2.6. Sulfate reduction rates
 2.7. Sediment characteristics and Thioploca biovolume determination
 2.8. Polyphosphate in Thioploca cells
 2.9. Modeling of pore water data
3. Results
 3.1. Description of sediment
 3.2. Thioploca
 3.3. Sulfate reduction
 3.4. Sulfur and iron in pore water and sediment
 3.5. Ammonium in pore water
 3.6. Phosphate in pore water and sediment
 3.7. Calcium in pore water
4. Discussion
 4.1. Thioploca populations
 4.2. Mineralization of organic matter
 4.3. Thioploca and phosphate
 4.4. Remobilization of phosphate to the pore water
5. Conclusion
Acknowledgements
References


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