The trace element composition of suspended particulate matter in the Amundsen Sea Polyna, West Antarctica
The Amundsen Sea Polynya is one of the most productive regions in the Southern Ocean. Since macronutrients are abundant, natural iron (Fe) fertilization is likely responsible for large seasonal phytoplankton blooms; however, little is known about the mechanism of Fe supply to this polynya, in partic...
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| Format: | Text |
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2013
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| Online Access: | https://dx.doi.org/10.7282/t3bk19dj https://rucore.libraries.rutgers.edu/rutgers-lib/41780/ |
| Summary: | The Amundsen Sea Polynya is one of the most productive regions in the Southern Ocean. Since macronutrients are abundant, natural iron (Fe) fertilization is likely responsible for large seasonal phytoplankton blooms; however, little is known about the mechanism of Fe supply to this polynya, in particular with respect to various forms of particulate Fe. During December 2010 and January 2011, water samples were filtered by contamination-free methods to collect suspended particulate matter; subsamples of these filters were digested or chemically leached, and analyzed for Fe and a suite of other metals. High crustal particle concentrations were measured throughout the polynya, with highest values observed where strong northward flow emanates from under the melting Dotson Ice Shelf, propelling particulate and dissolved Fe to sub-euphotic zone depths in the central polynya. Potentially bioavailable fractions were investigated by comparing chemically leachable fractions to “excess” (non-crustal) fractions, calculated from average crustal element/aluminum ratios. The Dotson Outflow Station has high concentrations of both total and labile particulate Fe fractions, suggesting substantial inputs of potentially bioavailable particulate Fe to the polynya, fueling phytoplankton blooms. In the euphotic zone, suspended matter analyses can reveal cellular metal concentrations of the phytoplankton assemblage. Non-crustal Zn/P is exceptionally high throughout the polynya compared to most literature values for marine phytoplankton, but is consistent with previous determinations in Antarctic waters near the Ross Sea. Both Zn/P and Cd/P show lower ratios in higher primary productivity polynya regions, suggesting a biodilution effect, competitive uptake antagonism with Fe, or reduced availability of dissolved Zn and Cd resulting from prior biological activity. In contrast, Cu/P is relatively high at the high productivity stations where Zn/P and Cd/P are low, and dissolved Cu is at minimum for the polynya. These high Cu/P ratios may reflect high quotas unique to bloom-dominating Phaeocystis antartica, suggestive of a Cu-requiring reductive Fe uptake pathway. |
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