T, light/UV, mixing, Fe, Si, ….

Climate change

C export

CO2,

CH4,

COVCH3I

DMS

DMSeN2O

aérosols

Structure of the

phytolankton community

CHX

General objective:

To contibute to improve our understanding and prediction of

the response of the Southern Ocean to the global climate change

bacteriaviruszooplankton

bacteriaviruszooplankton

General objective of KEOPS:

To contibute to improve our understanding and prediction of

the response of the Southern Ocean to climate change.

specific objectives

Identification of the mecanisms of natural iron fertilisation

of the Kerguelen Plateau.

Flux studies in contrasting environments:

Process studies:

To improve the knowledge of the biogeochemical processes involved

in the C02 biological pump and biogas production,

focusing on their responses to change in forcing parameters:

iron supply, statrification, light (visible and UV),

specific objective : Identification of the mecanisms of natural iron fertilisation

of the Kerguelen Plateau.

Which mechanisms are responsible for the enrichment of deep water with iron?

Contact with the margin when deep waters circulates around the plateau

Remineralisation of sinking biogenic material after a massive bloom

Release from the shelf sediment

Dissolution of lithogenic particles issued from island

What is the major mechanism of the upward transfer of iron from deep waters

to the surface layer?

Strong interaction between tidal currents and the bottom topography generates

internal tides activity tranfering deep waterto the surface.

0 m

Strategy for objective 1

Temperature measured using sensors attached to  pengins (Chassarin et al. 2001)

100 m

150 M

2

1

A1

A11

B11

C11

B1

C1

A5

B5

C5

Transect A

Transect B

Transect C

specific objective: Flux studies in contrasting environments:

Quantification of the flux of gases and aerosols at the ocean atmophere interface.

We will focuse on gases important in atmospheric chemistry and climate and on aerosol

as a source of iron to the ocean.

Quantification of the flux of carbon exported below the depth ofthe winter mixed layer.

Strategy for objective 2

Parameters

Gases: CO2, DMS, DMSe, CH4, CO, N2O,

CHNM, CHX, CHNO3.

Aerosols:

Carbon export: POC, PON, BSi, CaCO3, Ba,

234Th, 230Th, 232Th, delta ( 13C, 15N, 30Si ).

Two contrasting environments

Process studies:

To improve the knowledge of the biogeochemical processes involved

in the C02 biological pump and biogas production,

focusing on their responses to change in forcing parameters:

iron supply, statrification, light (visible and UV),

Characterization of phytoplankton community: What physical and chemical

factors regulate phytoplankton growth and species composition.

Shifts in the structure of the phytoplankton communities in response to changes in

the forcing parameters : iron light (visible and UV), stratification.

Do biological activity compete with photochemical process for the production of biogenic

gases and iron speciation?

Strategy for objective 3

In situ observations in the two contrasting environments and along the gradients .

On Board Experiments (OBEX)

OBEX 1: Factors controling the growth of microbial community.

OBEX 2: The impact of grazing on the iron speciation and the production of gases.

OBEX 3: The impact of bacterial degradation and solar radiation on iron speciation

and the production of biogenic gases.

OBEX 4: The impact of viral lysis on iron speciation and bioavailability.

Foreign participations

NIOZ (NL)

CSIRO and ACE CRC.

UVB

NIWA (NZ) Cliff Law (biogenic gases)

T1171Day 12.3

0

20

40

60

80

100

120

140

95 105 115% N2O saturation

Depth

(m

)

26.9 27.1 27.3 27.5Density (t)

Changes in nitrous oxide production stimulated by biological response to

Fe addition during SOIREE (Law et al, 2001)

Development of [N2O]max coincident with integrated chlorophyll during SOIREE

Increase in [N2O] max at base of mixed layer during SOIREE

0

20

40

60

80

100

120

140

160

0 1 2 3 4 5 6 7 8 9 1011121314

Time (days)

Inte

garte

d ch

lorop

hyll m

g Ch

la m

-2)

0

0.2

0.4

0.6

0.8

1

1.2

Max

imum

N2O

* nm

ol/l)

And also CH4 and CO.

Foreign participations

NIOZ (NL)

CSIRO and ACE CRC.

UVB

NIWA (NZ) Cliff Law (biogenic gases)

NIWA (NZ) Phil Boyd (iron phytoplankton dynamics)

Univ. Delaware Dave Hutchins ? (phytoplankton, chemostat with change in forcing parameters, Fe, pCO2…)