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Particulate Biogenic Silica
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To assist in the interpretation of the data, it can be displayed
using the Hawaii Ocean Time-series Data Organization &
Graphical System (HOT-DOGS©).
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Analytical Method
Samples for elemental analyses of Particulate biogenic silica were
collected into 4L polyethylene carboys; filtered through 47 mm
polycarbonate filter holders; onto 47 mm polycarbonate, membrane
filters; and placed into 50 ml polypropylene centrifuge tubes. Time
course subsamples (1.5, 3, 4.5, 6.5 and 24 hours) were measured
colorimetrically to distinguish Lithogenic-Si from Biogenic-Si
(DeMaster, 1981). The average precisions during 2006 determined from
duplicate analyses are presented in the Table below.
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| PSi
| Cruise
| mean CV
(%)
| mean SD
(ng/l)
| N
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| 177
| 56.9
| 6.827
| 2
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| 178
| 12.5
| 1.814
| 2
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| 179
| 12.1
| 1.534
| 1
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| 180
| 6.5
| 0.704
| 2
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| 182
| 61.2
| 4.964
| 2
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| 183
| 8.2
| 1.595
| 2
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| 184
| 17.0
| 4.458
| 2
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| 185
| 3.2
| 0.269
| 2
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| 186
| 21.5
| 1.796
| 1
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| 187
| 19.6
| 1.669
| 1
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| 188
| 32.2
| 3.270
| 2
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| Mean
| 22.8
| 2.627
| 11
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Results
Particulate biogenic silica (PSi) concetrations in the surface ocean
over the last 10 years of the program are shown in Figure 68 and Figure 69.
PSi typically ranges from < 10 to about 25 nmol kg-1 in the
upper 100 m of the water column. During the summer months in 1998, 2000
and 2005, PSi increased dramatically in the upper 50 m of the water. This
feature appears associated with a large bloom of diatomes, as evidenced
from the sharp increases in fucoxanthin (Figure
48)
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