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

Philippe Lebaron Ingrid Obernosterer

Observatoire Océanologique, Banyuls-sur-mer

- 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

The sea-surface microlayer

Ions moleculeshydrophobic

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)

Pre

dato

r pr

essu

re

Hea

t con

duct

ion

0.1 (10 cm)G

as d

iffu

sion

Vironeuston

Sur

face

laye

r

Sur

face

cen

tila

yer

Sur

face

mil

lila

yer

Sur

face

mic

rola

yer

Sur

face

nan

olay

er

Air - water interface

Dissolved and ParticulateOrganic and Inorganic

MatterNeuston

Organic Matter

Phytoneuston

Protists

Bacterioneuston Viruses

Metazoans

Gases

Organic and Inorganic Particles

Gases

Sea

-su

rfac

e M

icro

laye

r

Sub-surface Waters

e.g. O2, CO2,DMS, CH4,

O2, CO2, N2

Photo--lysis

Bubble Ejection

Atm

osp

her

eSea-surface microlayer - Atmosphere Interactions

The samplersMetal screen: 400 microns

Glass plate : 50-70 microns

Metal screen - 200µm mesh

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

1.1 1.2

11 13

5.4 2.8

1.8 0.7

9.9 1.0

10 n.d.

Bacterial Production

Community Respiration 7.5 n.d.

1.2 1.0

Wind speed

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.

A B

Linking structure and function

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

Sampling

Sea-surface microlayer Water Column

Zodiac Metal Screen & Glass Plate

time = f(Vol of water)

Metal Screen 5 L/hGlass 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 ???