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The distribution of biogenic and lithogenic silica and the composition of particulate organic matter in the Scotia Sea and the Drake Passage during autumn 1987

Treguer, P., Nelson, D. M., Gueneley, S., Zeyons, C., Morvan, J. & Buma, A., 1990, In : Deep-Sea Research I. 37, 5, p. 833-851 18 p.

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  • Paul Treguer
  • David M Nelson
  • Stephanie Gueneley
  • Christiane Zeyons
  • Jean Morvan
  • Anita Buma
Abstract--Suspended matter was collected from surface, deep and bottom waters during the
ANTIPROD 3 cruise (autumn 1987) at six stations located in the Scotia Sea and analysed for
biogenic silica (BSi), lithogenic silica (LSi), particulate organic carbon (POC) and nitrogen (PON).
The composition of suspended particulate matter also was determined in the photic layer at 10
stations situated in the Scotia Sea, the Drake Passage, the Bransfield Strait and near the ice edge.
While nutrient levels in surface waters were always high, phytoplankton biomass was typically
quite low during this season, as demonstrated by the low concentrations of chlorophyll a (<0.3 mg
m-3), BSi (< 1/~mol 1-1), POC (<6/~mol 1-1) and PON (< 1/~mol I-1). Nevertheless enhanced
concentrations were measured in the vicinity of the Polar Front in the Scotia Sea (Chl a = 1.06 mg
m -a, BSi = 2.32/~mol 1-1 ) and within a diatom-dominated phytoplankton patch (Chl a = 0.48 mg
m-3; BSi = 4.24/~mol 1-1) in the Drake Passage, within the area influenced by the Antarctic
Divergence. In surface waters the contribution of lithogenic to total particulate silica was generally
lower than 20%. However in the vicinity of icebergs, the Antarctica coast, as well as in areas
receiving eolian inputs in the northern part of the study area, the proportion of LSi was much
higher (rising to 89%). Concentrations of both biogenic and lithogenic silica were uniformly low in
Warm Deep Water (<0.2/~mol 1-1). The dramatic enhancement of their concentrations in bottom
waters (where BSi reached levels as high as 2.6/~mol 1-1) is interpreted as resulting mainly from
local resuspension due to bottom currents. The mean POCJPON mole ratio in the surface layer was
6.4 + 0.3, but increased to 10.1 + 0.6 in the deep and bottom water, which suggests that the
nitrogen recycling is more rapid than that of carbon in Antarctic deep waters. BSi/POC mole ratios
in surface waters exhibited values two to three times higher than typically found in pure diatom
cultures. These results are consistent with previous observations in other sectors of the Southern
Ocean showing that the biogenic particulate material is unusually rich in sifica.
Original languageEnglish
Pages (from-to)833-851
Number of pages18
JournalDeep-Sea Research I
Volume37
Issue number5
Publication statusPublished - 1990

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