Synapomorphies that distinguish the fungi: Absorptive heterotrophy Chitin in cell walls.
Flux studies in contrasting environments (obj. 2) The role of heterotrophy (bact. microzoo)
description
Transcript of Flux studies in contrasting environments (obj. 2) The role of heterotrophy (bact. microzoo)
What is the impact of natural iron fertilization- On the structure of the microbial food web- On the functioning of the microbial food web- On the fate of primary production
And How the magnitude of carbon fluxes (grazing, mineralization) is affected by iron availability ?
We will focus on two axes to differentiate heterotrophic responses
- Direct vs indirect effects on heterotrophic bacteria, DOC utilization and respiration- Cascade effect on the trophic web
Specific objectives
Quantification of the carbon flux exported – Obj. 2.2-
ciliatescopepods
heterotrophic bacteria
picophytoplanktonnanophytoplankton
microphytoplankton
DOC
P, N
nanoflagellates
Silicates
CO2O2
O2CO2
Gross Communityproduction GCPand Dark CommunityRespiration DCR
? IRON ?
? ? ? ? ? ? ? ?? ? ?? ? ?? ? ?? ?
ciliatescopepods
heterotrophic bacteria
picophytoplanktonnanophytoplankton
microphytoplankton
DOC
P, N+ iron
nanoflagellates
Silicates
CO2O2
O2CO2
Gross Communityproduction GCPand Dark CommunityRespiration DCR
Direct effect of IRON on heterotrophs 1) Are bacteria Fe limited?
Is there changes in bacterial biomass, ectoenzymatic activities, production, respiration ?
ciliatescopepods
heterotrophic bacteria
picophytoplanktonnanophytoplankton
microphytoplankton
DOC
P, N + Fe
nanoflagellates
Silicates
CO2O2
O2CO2
Gross Communityproduction GCPand Dark CommunityRespiration DCR
Indirect effects of IRON on microbial food web 1. Is the response of the microbial food web a cascade effect from Phytoplankton stimulation?
What is the fate of the phytoplankton ?Phytoplankton growth phytoplankton grazing rates, abundance of predators, relations between predators?
?
? grazing ?sinking ?
ciliatescopepods
heterotrophic bacteria
picophytoplanktonnanophytoplankton
microphytoplankton
DOC
nutrients
nanoflagellates
Silicates
CO2O2
O2CO2
Gross Communityproduction GCPand Dark CommunityRespiration DCR
Heterotrophy and remineralisation Indirect effects of IRON on microbial food web: 2. Do bacteria benefit from the carbon derived from Fe stimulated primary production?
Does the Fe fertilization influence- the production and respiration of bacterioplankton and consequently the BGE ?- the factors limiting bacterial activity (Fe vs DOC)
Heterotrophic and phototrophic nanoflagellates- epifluorescence microscopy - size classes - biovolumes- carbon equivalents
Ciliates- formol/lugol fixation- Sedimentation and counting on inverted microscope equipped for fluorescence- size classes / taxonomy
+ with flow cytometry data (pico autotrophs, heterotrophic bacteria) and the microphytoplankton mesozooplancton stocks
Tools for studying biomasses
1. Structure of the food web in terms of stocks
Bacterial production
3H-leucine incorporation into proteins, with micro-centrifuge technique
Gross community production and Dark community respiration : 24h variations of O2 in Winkler flasks, in situ-simulated conditions (running water bathes and screens)
Bacterial ectoenzymatic activity
Hydrolysis of fluorogenic substrates (aminopeptidase, glucosidase)
Grazing fluxesUse of fluorescent labelled preysFluorescent labelled bacteria for bacterial grazing by flagellatesFluorescent labelled algae for grazing of nanophytoplankton by ciliates.
Tools for studying fluxes
2. Fluxes
FLS (fluorescently labelled Synechococcus)Synechococcus analog
FLS
FLA (fluorescently labelled algae, Rublee & Gallegos 1989)Nanophytoplankton analog
FLA Nanochloropsis sp. (2-4 μm)
Grazing of pico and nanoautotrophs by ciliates
Tools for studying fluxes
M2
D6
D5D4D3D2
D1
A5
Where do we sample ? across gradients
Vertical profiles (euphotic zone – 0-200m)
Kerguelen Plateau A5
Open Sea D6
The transect Plateau – Open Sea 5 stations D1 to D5
Sampling strategy
In situ
Profiles : standing stocks and BP, O2/CO2 fluxesSurface layer : grazing, growth of heterotrophs
We need : - to sample at the same time of the day every profile-to coincide with PP (14C) rosette, nutrients, DOC profile, flow cytometry, bacterial taxonomy, FISH
Volumes necessary :BP, stocks (HNAN/PNAN, ciliates) : 750 mlO2/CO2 fluxes : Grazing bact, nanophyto (surface only) : 2 litres Growth (cil, flag, surface only): 10 lt
on-board experiments
Process studies:Effect of Iron limitation on microbial food webs
OBEX 1 : microb comm. growth, on-board experimentsResponse of the microbial food web Parameters to follow- BP (all time points)- HNAN/PNAN, ciliates stocks (T0h, T final)- grazing fluxes (T0h, Tfinal)
OBEX 4, OBEX 3< 0,8 µm mesocosms in the dark?Direct iron effect on bacteria- BP- O2 consumption BGE (bacterial growth efficiency)
- Other Collaborations?
Which material which person in charge
- Scintillation counter : Brest ? (Stéphane, Bernard ?)- Microcentrifuge (Urania ?, Markus ?)- Spectrofluorometer : possibly that desembarked after DYNAPROC ?
- One Millipore filtration apparatus (France, LMGEM)- One Millipore filtration apparatus (Urania MREN ? Markus LOV ?)- Inverted flux system (membranes 142 mm) (France, LMGEM)
- Refrigerated incubators ? Do we need on board ?