Balakrishnan Nair, T.M., Ittekkot, V., Shankar, R. and Guptha, M.V.S. (2005) Settling barium fluxes in the Arabian Sea: Critical evaluation of relationship with export production. Deep Sea Research Part II: Topical Studies in Oceanography, 52 (14-15). pp. 1930-1946. DOI https://doi.org/10.1016/j.dsr2.2005.06.003.

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Abstract

Time series measurement of biogenic and barium fluxes was made using nine sediment traps deployed in the western, central and eastern part of the Arabian Sea with the objective of evaluating barium as a proxy for surface ocean productivity. Our observations show a strong linear correlation between Baexcess fluxes and biogenic opal and organic carbon (Corg) fluxes, indicating a biogenic origin of particulate Ba. However, the correlation between biogenic and Baexcess fluxes is remarkably strong in areas of uniform productivity like the central Arabian Sea, when compared to regions of episodic productivity. The processes that precipitate particulate Ba appear to be less active during periods of high biogenic flux. A large discrepancy is documented between the export flux calculated from the barium-based algorithm [Francois, R., Honjo, S., Manganini, S.J., Ravizza, G.E., 1995. Biogenic barium fluxes to the deep sea: implications for paleoproductivity reconstruction. Global Biogeochemical Cycles 9, 289–303] and from Corg fluxes [Sarnthein, M., Winn, K., Duplessy, J.C., Fontugne, M.R., 1988. Global variations of surface ocean productivity in low and mid latitudes: influence on CO2 reservoirs of the deep ocean and atmosphere during the last 21,000 years. Paleoceanography 3, 361–399] at different depths. However, ∼35% increase in Ba fluxes and a concomitant increase in Ba/Corg ratios are documented between 919 and 2002 m water depth in the western Arabian Sea. This increase may be due either to barite formation within the fecal pellets of mesozooplankton thriving at deeper levels or to scavenging of Ba by Mn oxyhydroxides. Manganese oxyhydroxides seem to act as a prominent scavenging phase for particulate Ba when the Mnexcess content in the settling particles exceeds ∼200 ppm, especially in the western and central Arabian Sea where in situ precipitation of Mn oxides is reported. The estimated preservation efficiency of Ba in the Arabian Sea sediments ranges between 50% and 61%. This is two-fold higher than the global average, suggesting that Ba may be a promising proxy for paleoproductivity estimation.

Document Type:	Article
Programme Area:	UNSPECIFIED
Research affiliation:
Refereed:	Yes
Open Access Journal?:	No
DOI:	https://doi.org/10.1016/j.dsr2.2005.06.003
ISSN:	09670645
Date Deposited:	06 Apr 2020 09:59
Last Modified:	01 Oct 2020 13:01
URI:	http://cris.leibniz-zmt.de/id/eprint/3671

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