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VERTIGO PHYTOPLANKTON PROCESSES Philip Boyd and Mark Gall Apologies for my absence.

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Presentation on theme: "VERTIGO PHYTOPLANKTON PROCESSES Philip Boyd and Mark Gall Apologies for my absence."— Presentation transcript:

1 VERTIGO PHYTOPLANKTON PROCESSES Philip Boyd and Mark Gall Apologies for my absence

2 VERTIGO 1 – ALOHA – summary 2 PP profiles (ca. 180 and 220 mg C m -2 d -1 ) PP and stocks dominated by 0.2 – 2 micron fraction (66-90%) Few large cells (> 20 microns cells – 9% of PP) Fv/Fm – suboptimal – but higher at depth – N or P limited bugs Little change in [chl], PP etc during study

3 VERTIGO 2 – K2 – summary Distinct differences between 2 station occupations at K2 Deployment 1 –higher biomass and PP, (450 - 600 mg C m-2 d-1) PP and stocks dominated by >20 micron fraction (>40%) and < 2 microns (>40%) Fv/Fm – suboptimal – Fe limited as shown in perturbation expt Deployment 1 Deployment 2

4 VERTIGO 2 – K2 – summary Deployment 1 –higher biomass and PP, (300 - 450 mg C m-2 d-1) PP and stocks dominated by 60%), > 20 microns = 20% Fv/Fm – suboptimal – Fe limited as shown in perturbation expt Fe stress increases diatom sinking rates (Waite and Nodder, 2000)

5 Honda et al. (2006) GRL V Changes in the Proportion of diatoms Probably driven by small Changes in Fe supply This has been observed in NE Pacific (Boyd & Harrison, 1999) During the VERTIGO Occupation of K2 Cells were Fe-limited in HNLC waters

6 LINKING THE SURFACE AND THE SUBSURFACE OCEAN EP PP Algal size structure Where is the water column “particle factory”? Who is fixing the carbon? Who is producing ballasting Agents? Size-partitioning during K2 Chlorophyll Primary production BSi Floristics Pigments Use these to explore fate of Main primary producers

7 Size classes – who is there? CTD 39 > 20 um diatoms Pseudo-nitzschia sp. Chaetoceros sp. Coretheron, few dino’s < 5 um Synechococcus, Some ANAN and Prochlorococcus CTD 66 > 20 um Chaetoceros spp. < 5 um cells – as before

8 Size classes – BSi Occupation 2 > 20 micron cells comprise 80% of mixed layer BSi < 5% in < 2 micron fraction – diatom fragments? Similar trends to >150 m in BSi partitioning suggests strong surface supply

9 Modelling how different PP and size partitioning influence export flux H PNM MeC B Faecal-mediated flux Algal/faecal flux HOT EP ranges from 19 to 24 mg C m-2 d-1 (10-13% of PP) K2 Deployment 1 - EP ranges from 66 to 166 mg C m -2 d -1 (13-32% PP) Deployment 2 – EP ranges from 23 – 43 mg C m -2 d -1 (10-14% PP)

10 PHYTOPLANKTON PROCESSES i) Changes in both PP and community structure may result in a large shift in export production ii) Potential impact of episodic Fe supply on export – at K2 iii) HNLC vs. LNLC – little different in EP between HOT and K2 deployment 2 (10-14%) iv) Differences between K2 deployment 1 and 2 are a useful test of the relative role of the surface and subsurface ocean on export, sinking rates, b values etc.


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