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Comparison of Phytoplankton Dynamics in the North Atlantic and the North Pacific Slide 2 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 ) Slide 3 2 North Atlantic Box 19W - 21W, 49.5N - 50.5N North Pacific Box 144W - 146W, 49.5N - 50.5N Chlorophyll Phytoplankton Carbon from Particulate Backscatter (Behrenfeld et al., 2005) Slide 4 3 North Atlantic Box 19W - 21W, 49.5N - 50.5N North Pacific Box 144W - 146W, 49.5N - 50.5N Chl:C Ratio Slide 5 4 Observed Chl:C ratios at OSP Slide 6 5 Full Time Series Chlorophyll Phytoplankton Carbon from Particulate Backscatter (Behrenfeld et al., 2005) Atlantic: 20W-40WPacific: 160W-140W Slide 7 6 Full Time Series Atlantic: 20W-40WPacific: 160W-140W 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? Slide 8 7 Geider Model: max = b / (1 + b a I / (2 P c max )) + a b = 0.038 mg Chl / mg C, a = 0.002 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 ) Slide 9 8 Chlorophyll:Carbon Ratio observed calculated observed calculated Atlantic Pacific Slide 10 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 Slide 11 10 Chlorophyll:Carbon Ratio observed calculated observed calculated Atlantic Pacific Atlantic Pacific No growth limitation Strong growth limitation Atlantic Pacific Fan et al., subm. Slide 12 11 Soluble Fe Flux (Fan et al., submitted) Slide 13 12 Opal Flux (Wong & Matear, 1999) Ocean Station P, Sediment Trap Data Slide 14 13 Slide 15 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, 530% of the total backscattering could be associated with coccoliths (calcite plates detached from cells) and plated cells. Slide 16 15 Slide 17 16 Coccoliths (Balch et al., 2005) Slide 18 17 Slide 19 18 Mesozooplankton (Goldblatt et al., 1999) Slide 20 19 Bacterial Biomass (Sherry et al., 1999) Slide 21 20 Full Time Series Averaged: 20W-40WAveraged: 160W-140W Maximum Chl:C Ratio Nutrient Limitation Factor