comparison of phytoplankton dynamics in the north atlantic and the north pacific

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

2

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)

3

North Atlantic Box19ºW - 21ºW, 49.5ºN - 50.5ºN

North Pacific Box144ºW - 146ºW, 49.5ºN - 50.5ºN

Chlorophyll

PhytoplanktonCarbon fromParticulateBackscatter(Behrenfeld et al., 2005)

4

North Atlantic Box19ºW - 21ºW, 49.5ºN - 50.5ºN

North Pacific Box144ºW - 146ºW, 49.5ºN - 50.5ºN

Chl:C Ratio

5

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

6

Full Time Series

Chlorophyll

PhytoplanktonCarbon fromParticulateBackscatter(Behrenfeld et al., 2005)

Atlantic: 20ºW-40ºWPacific: 160ºW-140ºW

7

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?

8

�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)

9

Chlorophyll:Carbon Ratio

observed

calculated

observed

calculated

Atlantic

Pacific

10

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

11

Chlorophyll:Carbon Ratio

observed

calculated

observed

calculated

Atlantic

Pacific

Atlantic

Pacific

No growth limitation

Strong growth limitation

Atlantic

Pacific

Fan et al., subm.

12

Soluble Fe Flux (Fan et al., submitted)

13

Opal Flux (Wong & Matear, 1999)

Ocean Station P, Sediment Trap Data

14

15

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.”

16

17

Coccoliths (Balch et al., 2005)

18

19

Mesozooplankton (Goldblatt et al., 1999)

20

Bacterial Biomass (Sherry et al., 1999)

21

Full Time SeriesAveraged: 20ºW-40ºWAveraged: 160ºW-140ºW

MaximumChl:C Ratio

NutrientLimitationFactor