1. Structure of the microbial food webs at the air-water interface Philippe Lebaron Ingrid Obernosterer Observatoire Océanologique, Banyuls-sur-mer

2. - Study of the structure and function of biological communities in the sea-surface microlayer. -Characterization of the bacterial community structure in the oligotrophic open ocean. -Linking bacterial activity to major phylogenetic groups. Objectives

3. The sea-surface microlayer Ions molecules hydrophobic surfactants hydrophilic surfactants Bacterioneuston Phytoneuston Zooneuston 10-9 10-8 10-7 10-6 (1µm) 10-5 10-4 10-3 (1 cm) 0.01 Depth (m) Predator pressure Heat conduction 0.1 (10 cm) Gas diffusion Vironeuston Surface layer Surface centilayer Surface millilayer Surface microlayer Surface nanolayer Air - water interface

4. Dissolved and Particulate Organic and Inorganic Matter Neuston Organic Matter Phytoneuston Protists Bacterio neuston Viruses Metazoans Gases Organic and Inorganic Particles Gases Sea-surface Microlayer Sub-surface Waters e.g. O 2, CO 2, DMS, CH 4, O 2, CO 2, N 2 Photo- -lysis Bubble Ejection Atmosphere Sea-surface microlayer - Atmosphere Interactions

5. The samplers Metal screen: 400 microns Glass plate : 50-70 microns Metal screen - 200µm mesh

6. Enrichment factors for the sea-surface microlayer in the Mediterranean Sea Metal Screen Glass Plate Bacterial Abundance Cultivable Bacteria Chlorophyll a Phaeophytin Particulate Organic Carbon Flagellates 1.11.2 11 13 5.4 2.8 1.8 0.7 9.9 1.0 10 n.d. Bacterial Production Community Respiration 7.5n.d. 1.2 1.0

7. Wind speed

8. Paenibacillus glucanolyticus AB073189 (SML) Planococcus rifietoensis AJ493659 (SML) Exiguobacterium aurantiacum X70316 (5 strains SU) Aeromicrobium erythreum AF005021 Aeromicrobium marinum AY166703 SML – 020 Nocardioides sp. AJ316318 Nocardioides jensenii Z78210 Blastococcus aggregatus L40614 (SU) SML – 014 Corynebacterium ammoniagenes X84440 Dietzia maris Y18883 (2 strains SML) Salinibacterium amurskyense AF539699 Marine bacterium AY188942 UW – 077 Microbacterium kitamiense AB013920 (SML) Microbacterium esteraromaticum AB099658 (SML) Brachybacterium arcticum (n.p.) AF434185 (SML) Brachybacterium sacelli AJ415383 Arthrobacter agilis X80748 (3 strains SML) Arthrobacter nitroguajacolicus AJ512504 0.01 FHGC Actinobacteria FLGC Phylogenetic tree based on the 16S rDNA sequences of isolates belonged to the FHGC group. The tree was created using neighbor-joining method. The bar indicates a Kimura distance of 0.01. Linking structure and function

9. Measurements and Methods proposed Characterization of the sea-surface microlayer (SML) -Sampling the SML (Metal Screen and Glass Plate) -Enumeration of heterotrophic and autotrophic community (flow cytometry) -Pigment analysis -POC and DOC -Activity measurements : Primary production and Community Respiration (O 2 -measurements), Bacterial Production ( 14 C-Leucine incorporation) -Bacterial Diversity : SSCP and Cloning; Isolation of bacterial strains -MAR-FISH Measurements in the water column -Bacterial Diversity : SSCP -MAR-FISH

10. Sampling Sea-surface microlayer Water Column Zodiac Metal Screen & Glass Plate  time = f(Vol of water) Metal Screen5 L/h Glass Plate2L/h (2 plates) 1 sampling ≈ 1.5-2h, with 3 persons abord the zodiac Frequency: 2 samplings/station - noon - midnight High resolution depth profile (0-5m) (limited to 2-3 long stations) Each Station -5 depths (above, below and in the DCM, 2 depths > 500 m ) -Bacterial abundance and diversity -MAR-FISH -Water volume needed: 1.5-2L -- Aerosols ???