Comparison of Phytoplankton Dynamics in the North Atlantic and the North Pacific
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North Pacific North Atlantic
Temporal standard deviationof chlorophyll (mg m-3)
Temporal standard deviationof chlorophyll (mg m-3)
Temporal standard deviationof carbon biomass (mg m-3)
Temporal standard deviationof carbon biomass (mg m-3)
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North Atlantic Box19ºW - 21ºW, 49.5ºN - 50.5ºN
North Pacific Box144ºW - 146ºW, 49.5ºN - 50.5ºN
Chlorophyll
PhytoplanktonCarbon fromParticulateBackscatter(Behrenfeld et al., 2005)
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North Atlantic Box19ºW - 21ºW, 49.5ºN - 50.5ºN
North Pacific Box144ºW - 146ºW, 49.5ºN - 50.5ºN
Chl:C Ratio
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Observed Chl:C ratios at OSPMeasurements at OSP (Varela & Harrison, 1999)
Mar-93 Feb-94 May-93 May-94 Sep-92 Sep-94
Chl mg m-2 14.6 12.4 23.2 14.2 35.1 19.7
PN mg m-2 43.5 60.6 67.2 69.2 111.5 77.5
PC mg m-2 696 969.6 1075.2 1107.2 1784 1240
Chl:C 0.021 0.013 0.022 0.013 0.020 0.016
Feb Mar Apr May Jun Jul Aug Sep
1992 0.020
1993 0.021 0.022
1994 0.013 0.013 0.016
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Full Time Series
Chlorophyll
PhytoplanktonCarbon fromParticulateBackscatter(Behrenfeld et al., 2005)
Atlantic: 20ºW-40ºWPacific: 160ºW-140ºW
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Full Time SeriesAtlantic: 20ºW-40ºWPacific: 160ºW-140ºW
Chl:C Ratio
Why are summer Chl:C ratios lower in the Pacific than the Atlantic?
More light in the Pacific? Stronger nutrient stress in the Pacific?
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�Geider Model:
max = b / (1 + b • a • I / (2 • Pcmax)) + a
b = 0.038 mg Chl / mg C, a = 0.002 mg Chl / mg C
a = 3.0E-5 gChl-1 gC W-1 m2 s-1, Pcmax = 3.0E-5 s-1
I = growth irradiance (W m-2)
Atlantic
Atlantic
Atlantic
Pacific Pacific
Pacific
Chlorophyll:Carbon RatioObserved Chl:C Growth Irradiance Ig
Calc. Chl:C = f(Ig)
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Chlorophyll:Carbon Ratio
observed
calculated
observed
calculated
Atlantic
Pacific
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Chlorophyll:Carbon Ratio
observed
calculated
observed
calculated
Atlantic
Pacific
Atlantic
Pacific
�Nutrient (and Temperature) Limitation Index:
f(N,T) = obs / max
obs = observed Chl:C
max = calc. max. Chl:C from Geider, assuming no nutrient limitation
No growth limitation
Strong growth limitation
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Chlorophyll:Carbon Ratio
observed
calculated
observed
calculated
Atlantic
Pacific
Atlantic
Pacific
No growth limitation
Strong growth limitation
Atlantic
Pacific
Fan et al., subm.
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Soluble Fe Flux (Fan et al., submitted)
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Opal Flux (Wong & Matear, 1999)
Ocean Station P, Sediment Trap Data
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Particulate Backscatter (Stramski et al., 2004)
“More recently, it was suggested that in typical non-bloom open ocean waters,
phytoplankton or all the microorganisms account for a relatively small fraction of
particulate backscattering, and that most of the backscattering may be due to non-living
particles, mainly from the submicron size range (Morel & Ahn, 1991; Stramski &
Kiefer, 1991). The potential role of small-sized organic detritus as a major source of
backscattering was emphasized but the significance of minerals was not excluded (see
also Stramski, Bricaud, & Morel, 2001). (…)
The optical impact of coccolithophorid phytoplankton (coccolithophores) can be,
however, very important (Balch, Kilpatrick, Holligan, Harbour, & Fernandez, 1996).
These phytoplankton species produce calcite scales called coccoliths that are
characterized by a high refractive index. It was estimated that even outside the
coccolithophore bloom, 5–30% of the total backscattering could be associated with
coccoliths (calcite plates detached from cells) and plated cells.”
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Coccoliths (Balch et al., 2005)
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Mesozooplankton (Goldblatt et al., 1999)
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Bacterial Biomass (Sherry et al., 1999)
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Full Time SeriesAveraged: 20ºW-40ºWAveraged: 160ºW-140ºW
MaximumChl:C Ratio
NutrientLimitationFactor