Key players of the phytoplankton communities 5 µm 50 µm 0.5 µm50 µm

Key players of the phytoplankton communities

M2 D6 D5 D4 D3 D2 D1 A5 A1 A11 B11 C11 C1 B1 KERFIX

Key players of the phytoplankton communities N D JF M A MJJtA SO N D JF M A MJ A SO N D JF Total cell Carbon, µg L -1 M2 Kopczynska E.E., Fiala M., and Jeandel C., Annual and interannual variability in phytoplankton at a permanent station off Kerguelen Islands, Southern Ocean, Polar Biology, 20 (5), , 1998.

Key players of the phytoplankton communities N D JF M A MJJtA SO N D JF M A MJ A SO N D JF Total cell Carbon, µg L Algal groups as % of total cell C Kopczynska et al., 1998

Key players of the phytoplankton communities N D JF M A MJJtA SO N D JF M A MJ A SO N D JF Algal groups as % of total cell C Diatoms total Dinoflagellates naked flagellates picoplankton Coccolithophorids Kopczynska et al., 1998

Key players of the phytoplankton communities N D JF M A MJJtA SO N D JF M A MJ A SO N D JF Algal groups as % of total cell C Diatoms Kopczynska et al., 1998 low contribution dominant species : Fragilariopsis kerguelensis, Thalassionema nitzschioides

highest contribution dominant species : Prorocentrum spp., Gymnodinium spp., heterotrophic species of Protoperidium spp. and Gyrodinium spp. during summer. total Dinoflagellates Key players of the phytoplankton communities N D JF M A MJJtA SO N D JF M A MJ A SO N D JF Algal groups as % of total cell C Kopczynska et al., 1998

Key players of the phytoplankton communities N D JF M A MJJtA SO N D JF M A MJ A SO N D JF Algal groups as % of total cell C naked flagellates Kopczynska et al., 1998 low contribution during biomass peaks dominant groups : Prymnesiophyceae (Chrysochromulina spp.), Prasinophyceae (Pyramimonas spp.), and Cryptophyceae (Hillea fusiformis)

occasionally abundant dominant species : Coccolithophorids Key players of the phytoplankton communities N D JF M A MJJtA SO N D JF M A MJ A SO N D JF Algal groups as % of total cell C Emiliania huxleyi Kopczynska et al., 1998

Surface temperatures (> 2°C) are compatible with Emiliania huxleyi and Fragilariopsis kerguelensis Key players of the phytoplankton communities

M2 Blain S., Tréguer P., Belviso S., Bucciarellia E., Denis M., Desabre S., Fiala M., Martin Jézéquel V., Le Fèvre J., Mayzaud P., Marty J.-C., and Razouls S., A biogeochemical study of the island mass effect in the context of the iron hypothesis: Kerguelen Islands, Southern Ocean, Deep-Sea Research, 48 (1), , 2001.

Key players of the phytoplankton communities Blain et al., 2001 – 4-10 October 1995

Objective 3 :Knowledge and quantification of biogeochemical processes and their responses to changes in the forcing parameters. 3.1)Structure of phytoplankton communities. KEOPS will address the question "what physical and chemical factors regulate phytoplankton growth and species composition?" 3.2) Shifts in the structure of the phytoplankton communities in response to changes in the forcing parameters. (KEOPS will focus on the following forcing parameters: iron, light (visible and UV), stratification. 3.3) Do biological activity compete with photochemical processes for the production of biogenic gases and iron speciation? Key players of the phytoplankton communities

3.1)Structure of phytoplankton communities. KEOPS will address the question "what physical and chemical factors regulate phytoplankton growth and species composition?" Detailed topics include: 3.1.1)Characterization of phytoplankton communities in contrasted environments. Special attention will be paid to the major biogeochemical players: diatoms, Phaeocystis, coccolithophorids, cryptophyceans and picoplankton )Identification, hierarchisation, and parameterization of the processes that control the structure of the phytoplankton communities )Impact of the structure of the phytoplankton community on the fluxes of chemical compounds that are relevant for climate )Impact of the structure of the phytoplankton community on the flux of carbon exported below the depth of the mixed layer Objective 3 :Knowledge and quantification of biogeochemical processes and their responses to changes in the forcing parameters. Key players of the phytoplankton communities

3.2) Shifts in the structure of the phytoplankton communities in response to changes in the forcing parameters. (KEOPS will focus on the following forcing parameters: iron, light (visible and UV), stratification. The processes will be investigated mainly in the surface layer ) How will the forcing parameters impact the processes controlling the production of chemical compounds that are relevant for climate? 3.2.2) How will the forcing parameters impact the processes controlling the export of carbon below the depth of the mixed layer? 3.2.3) What is the feedback of biological activity on iron speciation? Objective 3 :Knowledge and quantification of biogeochemical processes and their responses to changes in the forcing parameters. Key players of the phytoplankton communities