Geochemical Particle Fluxes in the Southern Indian Ocean Seasonal Ice Zone: Prydz Bay Region, East Antarctica

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Marine Science


Time-series sediment traps were deployed between December 1998 and January 2000 and from March 2000 to February 2001 at two offshore Prydz Bay sites within the seasonal ice zone (SIZ) of the Southern Indian Ocean located between 62-63degreesS and 73-76degreesE to quantify seasonal biogeochemical particle fluxes. Samples were obtained from traps placed at 1400, 2400, and 3400 m during the first deployment year (PZB-1) and from 3300 m in the second deployment year (PZB-2). All geochemical export fluxes were highly seasonal with primary peaks occurring during the austral summer and relatively low fluxes prevailing through the winter months. Secondary flux peaks in mid-winter and in early spring were suggestive of small-scale, sea-ice break-up events and the spring retreat of seasonal ice, respectively. Biogenic silica represented over 70% (by weight) of the collected trap material and provided an annual opal export of 18 g m(-2) to 1 km and 3-10 g m(-2) to 3 km. POC fluxes Supplied ail annual export of approximately 1 g m(-2), equal to the estimated ocean-wide average. Elevated particulate C(org)/C(inorg) and Si(bio)/C(inorg), molar ratios indicate a productive, diatom-dominated system, although consistently small fluxes of planktonic foraminifera and pteropod shells document a heterotrophic source of carbonate to deeper waters in the SIZ. The observation of high Si(bio)/C(org) ratios and the delta(15)N time-series data suggest enhanced rates of diatom-POC remineralization in the upper 1000 m relative to (bio)SiO(2). The occurrence in this region of a pronounced temperature minimum, associated with a strong pycnocline and subsurface particle maximum at 50-100 m, may represent a zone where sinking, diatom-rich particulates temporarily accumulate and POC is remineralized. (C) 2003 Elsevier Ltd. All rights reserved.

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Deep Sea Research Part I: Oceanographic Research Papers





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