ORIGINAL PAPER Abundance and Chemical Speciation of Phosphorus in Sediments of the Mackenzie River Delta, the Chukchi Sea and the Bering Sea: Importance of Detrital Apatite Jia-Zhong Zhang • Laodong Guo • Charles J. Fischer Received: 14 August 2009 / Accepted: 8 November 2009 / Published online: 5 December 2009 Ó Springer Science+Business Media B.V. 2009 Abstract Utilizing a sequential extraction technique this study provides the first quan- titative analysis on the abundance of sedimentary phosphorus and its partitioning between chemically distinguishable phases in sediments of the Bering Sea, the Chukchi Sea and the Mackenzie River Delta in the western Arctic Ocean. Total sedimentary phosphorus (TSP) was fractionated into five operationally defined phases: (1) adsorbed inorganic and exchangeable organic phosphorus, (2) Fe-bound inorganic phosphorus, (3) authigenic carbonate fluorapatite, biogenic apatite and calcium carbonate-bound inorganic and organic phosphorus, (4) detrital apatite, and (5) refractory organic phosphorus. TSP con- centrations in surface sediments increased from the Chukchi Sea (18 lmol g -1 of dried sediments) to the Bering Sea (22 lmol g -1 ) and to the Mackenzie River Delta (29 lmol g -1 ). Among the five pools, detrital apatite phosphorus of igneous or meta- morphic origin represents the largest fraction (*43%) of TSP. The second largest pool is the authigenic carbonate fluorapatite, biogenic apatite as well as CaCO 3 associated phosphorus (*24% of TSP), followed by the Fe-bound inorganic phosphorus, representing *20% of TSP. The refractory organic P accounts for *10% of TSP and the readily exchangeable adsorbed P accounts for only 3.5% of TSP. Inorganic phosphorus dominates all of phosphorus pools, accounting for an average of 87% of the TSP. Relatively high sedimentary organic carbon and total nitrogen contents and low d 13 C values in the Mac- kenzie River Delta together with the dominance of detrital apatite in the TSP demonstrate the importance of riverine inputs in governing the abundance and speciation of sedimen- tary phosphorus in the Arctic coastal sediments. Keywords Phosphorus  Sediment  Apatite  Arctic Ocean  Mackenzie River Delta J.-Z. Zhang (&)  C. J. Fischer Ocean Chemistry Division, Atlantic Oceanographic and Meteorological Laboratory, National Oceanic and Atmospheric Administration, 4301 Rickenbacker Causeway, Miami, FL 33149, USA e-mail: Jia-Zhong.Zhang@noaa.gov L. Guo Department of Marine Science, University of Southern Mississippi, Stennis Space Center, MS 39529, USA e-mail: laodong.guo@usm.edu 123 Aquat Geochem (2010) 16:353–371 DOI 10.1007/s10498-009-9081-4