tom browning & heather bouman (oxford) mark moore (nocs)

JC068 Phytoplankton:Concentrations, Species, and Physiological Status

UK-GEOTRACES: Ocean Micronutrient Cycles WP5: Biological responses and cycling of micronutrients

Tom Browning & Heather Bouman (Oxford)Mark Moore (NOCS)

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

NASA MODIS January 2012 SST

Tem

pera

ture

(°C)

Sea Surface Temperature

JC068 CTD Temperature

Dept

h (m

)

45

30

15

0

Tem

pera

ture

(°C)30°S

40 °S

50°S

50°W 30 °W 10°W 10°E

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

Macronutrients

Nitr

ate

(µM

)Ph

osph

ate

(µM

)

Dept

h (m

)De

pth

(m)

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

Chlo

roph

yll C

once

ntra

tion

(m

g/m

3 )

NASA MODIS January 2012 Chlorophyll

Phytoplankton Biomass

JC068 Bottle Data: Chlorophyll ConcentrationDe

pth

(m)

10

1

0.1

0 Chlo

roph

yll C

once

ntra

tion

(m

g/m

3 )

30°S

40 °S

50°S

50°W 30 °W 10°W 10°E

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

JC068

D357

Chlorophyll Concentration (mg/m3)

Phytoplankton Biomass - Climatology

NASA MODIS Chlorophyll, 9 km2 resolutionMonth averaged

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

a ph(4

40)*

(m2 m

g-1)

Chlorophyll a-specific absorption at 440 nm: indicator of phytoplankton size

Larger aph(440)* = smaller cells

Phytoplankton Absorption

Samples run by Christian Utschig

Dept

h (m

)

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

Nanophytoplankton (2-20 µm) Picophytoplankton (0.2-2 µm)

ProchlorococcusSynechococcus

Total Bacteria

Analytical Flow Cytometry

Cell counts (cells/µL)

Dept

h (m

)De

pth

(m)

Dept

h (m

)

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

Fv/Fm: Thought to be influenced by phytoplankton species, light climate, micronutrients and macronutrients.

Fv/Fm in JC068 transect, a signature of Fe limitation

Phytoplankton PhotophysiologyFv/Fm

Dept

h (m

)

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

I C Fe0.1

0.150.2

0.250.3

0.350.4

0.45

Fv/F

m

I C Fe0.2

0.220.240.260.28

0.30.320.340.36

Fv/F

m

I C Fe0.2

0.250.3

0.350.4

0.450.5

0.550.6

Fv/F

m

ΔFv/

F m

= F

v/F m

Fe

amen

ded

bottl

e –

F v/

F m C

ontr

ol b

ottle

Control Fe addition (2 nM)Initial

Immediate analysis 24 hour incubation 24 hour incubation

Fe incubation experiments

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

=

Gough Island

Two dominant regimes:

1) Subtropical Gyre type waters• Low macronutrients• Fe replete• High irradiance (near surface)

2) AAC source waters• High macronutrients• Fe limited• Possible light limitation

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary

Chlo

roph

yll

Conc

entr

ation

(m

g/m

3 )

Dept

h (m

)

A: Warmer, low macronutrients, stratified

B: Colder, high macronutrients, deeper mixed layer

Low surface chlorophyll Higher surface chlorophyll

Dominated by smaller cells Dominated by large cells

Fe replete Fe limited

A B A

Samples to be run: HPLC; microscopy; N-Fixers; DNA

Introduction Chlorophyll Cell Size Phytoplankton Types Fe Limitation Summary D357

Pre-bloom (leg 1) and bloom (leg 2) conditionsCause: shallowing of mixed layer = increased light

Depressed mixed layer Fv/Fm = Fe limitationOctober – January: shift from Fe limited to macronutrient limited environment as bloom consumes macronutrients.

1st LEG

2nd LEG