Comparison of Phytoplankton Dynamics in the North Atlantic and the North Pacific

1 North PacificNorth Atlantic Temporal standard deviation of chlorophyll (mg m -3 ) Temporal standard deviation of chlorophyll (mg m -3 ) Temporal standard deviation of carbon biomass (mg m -3 ) Temporal standard deviation of carbon biomass (mg m -3 )

2 North Atlantic Box 19ºW - 21ºW, 49.5ºN ºN North Pacific Box 144ºW - 146ºW, 49.5ºN ºN Chlorophyll Phytoplankton Carbon from Particulate Backscatter (Behrenfeld et al., 2005)

3 North Atlantic Box 19ºW - 21ºW, 49.5ºN ºN North Pacific Box 144ºW - 146ºW, 49.5ºN ºN Chl:C Ratio

4 Observed Chl:C ratios at OSP

5 Full Time Series Chlorophyll Phytoplankton Carbon from Particulate Backscatter (Behrenfeld et al., 2005) Atlantic: 20ºW-40ºWPacific: 160ºW-140ºW

6 Full Time Series Atlantic: 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?

7 Geider Model:  max =  b / (1 +  b a I / (2 P c max )) +  a  b = mg Chl / mg C,  a = mg Chl / mg C a = 3.0E-5 gChl -1 gC W -1 m 2 s -1, P c max = 3.0E-5 s -1 I = growth irradiance (W m -2 ) Atlantic Pacific Chlorophyll:Carbon Ratio Observed Chl:CGrowth Irradiance I g Calc. Chl:C = f(I g )

8 Chlorophyll:Carbon Ratio observed calculated observed calculated Atlantic Pacific

9 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

10 Chlorophyll:Carbon Ratio observed calculated observed calculated Atlantic Pacific Atlantic Pacific No growth limitation Strong growth limitation Atlantic Pacific Fan et al., subm.

11 Soluble Fe Flux (Fan et al., submitted)

12 Opal Flux (Wong & Matear, 1999) Ocean Station P, Sediment Trap Data

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14 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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16 Coccoliths (Balch et al., 2005)

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18 Mesozooplankton (Goldblatt et al., 1999)

19 Bacterial Biomass (Sherry et al., 1999)

20 Full Time Series Averaged: 20ºW-40ºWAveraged: 160ºW-140ºW Maximum Chl:C Ratio Nutrient Limitation Factor