Schena,S.J., Reichart,G.J. and De Lange,G.J.(2005): Phosphorus burial as a function of paleoproductivity and redox conditions in Arabian Sea sediments. Geochimica et Cosmochimica Acta, 69(4), 919-931.


 In this study the response of sedimentary phosphorus (P) burial to changes in primary productivity and bottom water oxygen concentrations during the Late Quaternary is investigated, using two sediment cores from the Arabian Sea, one recovered from the continental slope and the other from the deep basin. The average solid-phase P speciation in both cores is similar, authigenic and biogenic ( fish debris) apatite make up the bulk of the P inventory (ca. 70%); whereas P adsorbed to iron oxides, organic P, and detrital apatite constitute minor fractions. Postdepositional redistribution has not significantly altered the downcore distribution of total solid-phase P. Phosphorus burial efficiencies are generally lower during periods of increased paleoproductivity. This is caused by (a) partial decoupling of the P export flux, consisting primarily of particulate organic P, and the P burial flux, consisting primarily of biogenic and authigenic apatite; and (b) the lack of increased rates of authigenic CFA formation during periods of higher P deposition. In addition, fluctuations in bottom water oxygen concentrations may have affected P burial in continental slope sediments. The results of this study indicate that higher primary productivity induces more efficient P cycling. On time scales exceeding the oceanic P residence time, this process may induce higher surface water productivity, thus creating a positive feedback loop. In the Arabian Sea, this feedback mechanism may have contributed to changes in sea surface productivity on sub-Milankovitch time scales because P, regenerated on the continental slopes of the Oman and Somalian coastal upwelling zones, is reintroduced into the photic zone relatively fast.』

1. Introduction
2. Material and methods
 2.1. Sample locations
 2.2. Solid-phase analysis
3. Results and discussion
 3.1. Burial of total solid-phase P
 3.2. Sedimentary P speciation
  3.2.1. Organic phosphorus
  3.2.2. Biogenic apatite
  3.2.3. Detrital and iron bound P
  3.2.4. Authigenic apatite
 3.3. Cause and implications of reduced PBE during periods of high productivity
4. Conclusions

Table 1. Partitioning of reactive P in sediments of the continental margin (Ruttenberg and Berner, 1993), the deep Pacific ocean (Filippelli and Delaney, 1996), and the Arabian Sea (this study), and estimates for the global average
Reactive P sinks Continental margin1 Pacific Ocean2 Arabian Sea3 Estimated global average
Froelich (1982) Ruttenberg (1993) This study
Organic P 22% 6% 10% 40% 22% 16%
Iron-P 16% 11% 12% 11% 22% 14%
Loosely sorbed-P 7% 5%





Fish-P <2%
Authigenic-P 38% <10% 34.5%
Note that the P speciation (organic P, iron bound P, and biogenic authigenic P fractions) in deep Pacific Ocean and Arabian Sea sediments is similar. The global average for the reactive P partitioning in marine sediments was estimated using the results for the continental margin (Ruttenberg, 1993; second column) and the Arabian Sea (deep-pelagic sediment; fourth column), assuming that the total annual sedimentary burial of reactive P in deep pelagic sediments is of the same magnitude as that in continental shelf areas (Froelich, 1984; Follmi, 1996). The P fraction associated with biogenic apatite for continental margin sediments is assumed to constitute half the authigenic P pool (likewise Arabian Sea sediments). Comparison with previous estimates (Froelich et al., 1982; Ruttenberg and Berner, 1993) indicates that burial of authigenic and biogenic apatite fraction is relatively more important than previously assumed, whereas organic P burial is of secondary importance.
1 Ruttenberg (1993).
2 Filippelli and Delaney (1996).
3 Average from NIOP455 and NIOP487.
4 Primarily consisting of P associated with biogenic apatite (fish debris).