Extractions and analyses of reactive phosphorus in the Bering Sea from IODP Holes 323-U1341A and 323-U1341B

• Main Authors: März, Christian, Poulton, Simon W, Wagner, Thomas, Schnetger, Bernhard, Brumsack, Hans-Jürgen
• Format: Dataset
• Language: English
• Published: PANGAEA 2016
• Subjects: 323-U1341A; 323-U1341B; Accumulation rate; phosphorus; reactive; Aluminium oxide; Bering Sea Paleoceanography; Calculated; DEPTH; sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Event label; Exp323; Integrated Ocean Drilling Program / International Ocean Discovery Program; IODP; Joides Resolution; Phosphorus excess; Ratio; Residual; Sample code/label; Sample ID; Silicon dioxide; Silicon excess; X-ray fluorescence spectrometer (Philips PW2400); Bering Sea
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.857261; https://doi.org/10.1594/PANGAEA.857261

To reconstruct the cycling of reactive phosphorus (P) in the Bering Sea, a P speciation record covering the last ~ 4 Ma was generated from sediments recovered during Integrated Ocean Drilling Program (IODP) Expedition 323 at Site U1341 (Bowers Ridge). A chemical extraction procedure distinguishing between different operationally defined P fractions provides new insight into reactive P input, burial and diagenetic transformations. Reactive P mass accumulation rates (MARs) are ~ 20-110 µmol/cm2/ka, which is comparable to other open ocean locations but orders of magnitude lower than most upwelling settings. We find that authigenic carbonate fluorapatite (CFA) and opal-bound P are the dominant P fractions at Site U1341. An overall increasing contribution of CFA to total P with sediment depth is consistent with a gradual "sink switching" from more labile P fractions (fish remains, Fe oxides, organic matter) to stable authigenic CFA. However, the positive correlation of CFA with Al content implies that a significant portion of the supposedly reactive CFA is non-reactive "detrital contamination" by eolian and/or riverine CFA. In contrast to CFA, opal-bound P has rarely been studied in marine sediments. We find for the first time that opal-bound P directly correlates with excess silica contents. This P fraction was apparently available to biosiliceous phytoplankton at the time of sediment deposition and is a long-term sink for reactive P in the ocean, despite the likelihood for diagenetic re-mobilisation of this P at depth (indicated by increasing ratios of excess silica to opal-bound P). Average reactive P MARs at Site U1341 increase by ~ 25% if opal-bound P is accounted for, but decrease by ~ 25% if 50% of the extracted CFA fraction (based on the lowest CFA value at Site U1341) is assumed to be detrital. Combining our results with literature data, we present a qualitative perspective of terrestrial CFA and opal-bound P deposition in the modern ocean. Riverine CFA input has mostly been reported from continental shelves ...