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Structure of the microbial food webs at the air-water interface

Structure of the microbial food webs at the air-water interface. Philippe Lebaron Ingrid Obernosterer Observatoire Océanologique, Banyuls-sur-mer. Objectives . - Study of the structure and function of biological communities in the sea-surface microlayer.

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Structure of the microbial food webs at the air-water interface

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

  2. Objectives • - 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.

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

  4. Bacterio neuston Metazoans Viruses Organic Matter Phytoneuston Protists Sea-surface microlayer - Atmosphere Interactions Gases Atmosphere Organic and Inorganic Particles Bubble Ejection e.g. O2, CO2, DMS, CH4, O2, CO2, N2 Dissolved and Particulate Organic and Inorganic Matter Photo- -lysis Neuston Gases Sea-surface Microlayer Sub-surface Waters

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

  6. Metal Screen Glass Plate 1.1 1.2 Bacterial Abundance 11 13 Cultivable Bacteria 5.4 2.8 Flagellates 1.8 0.7 Chlorophyll a 1.0 9.9 Phaeophytin 10 Particulate Organic Carbon n.d. 1.2 Bacterial Production 1.0 Community Respiration 7.5 n.d. Enrichment factors for the sea-surface microlayer in the Mediterranean Sea

  7. Wind speed

  8. Linking structure and function 0.01 Arthrobacter nitroguajacolicus AJ512504 Arthrobacter agilis X80748 (3 strains SML) Brachybacterium sacelli AJ415383 Brachybacterium arcticum (n.p.) AF434185 (SML) Microbacterium esteraromaticum AB099658 (SML) Microbacterium kitamiense AB013920 (SML) UW – 077 Marine bacterium AY188942 FHGC Actinobacteria Salinibacterium amurskyense AF539699 Dietzia maris Y18883 (2 strains SML) Corynebacterium ammoniagenes X84440 SML – 014 Blastococcus aggregatus L40614 (SU) Nocardioides jensenii Z78210 Nocardioides sp. AJ316318 SML – 020 Aeromicrobium marinum AY166703 Aeromicrobium erythreum AF005021 Exiguobacterium aurantiacum X70316 (5 strains SU) FLGC Planococcus rifietoensis AJ493659 (SML) Paenibacillus glucanolyticus AB073189 (SML) 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.

  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 (O2-measurements), Bacterial Production (14C-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 Water Column Sea-surface microlayer • Zodiac • Metal Screen & Glass Plate • time = f(Vol of water) Metal Screen 5 L/h Glass Plate 2L/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 ???

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