Distribution and Diagenesis of Phosphorus in the Deep-Sea Sediments of the Central Indian Basin
Date
2018Author
Linsy, P.
Nath, B.N.
Mascarenhas-Pereira, M.B.L.
Chauhan, T.
Sebastian, T.
PrakashBabu, C.
Kurian, S.
Miriyala, P.
Kazip, A.
Borole, D.V.
Khadge, N.H.
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A regional solid-phase phosphorus (P) speciation study in the Central Indian Basin (CIB) was carried out to elucidate the spatial distribution of sedimentary P species and P diagenesis in an oligotrophic setting. The results show that P enrichment is in the order of biogenic (P-bio) > authigenic (P-auth) > iron bound (P-Fe) > detrital (P-det) > organic (P-org) P. The higher concentrations of P-bio are found in siliceous oozes, which are attributed to high biological productivity in the overlying waters compared to pelagic clay region. High P-auth and P-det contents with low molar C-org/P-react ratios in the pelagic/red clays indicate the deposition of calcium fluorapatite and refractory material from the atmospheric input. The oxygenated bottom water promotes adsorption of P onto iron oxyhydroxides making the P-Fe an important sink. Remobilization of P within the sediments is limited because of well-oxygenated conditions and an efficient adsorption by iron oxyhydroxides and clay-sized sediments. A twofold increase in P-total and P-species is observed in hydrothermally altered, ferruginous sediments from a seamount flank suggesting an important role of hydrothermal processes in P cycling. The calculated P accumulation rate in the present study ranges between 0.6 and 11.7 μmol cm-2 kyr-1. The burial flux of P for the entire CIB (5.7 x 106 km2) is 0.01 x 1010 mol P per year which accounts for 0.05% of the global flux. The benthic P fluxes from the seawater to the sediments in the area range between 0.0093 and 0.133 μmol cm-2 kyr-1 indicating that the CIB sediments are an important sink for P.
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