Flux studies in contrasting environments (obj. 2)
Download
1 / 13

Flux studies in contrasting environments (obj. 2) The role of heterotrophy (bact. microzoo) - PowerPoint PPT Presentation


  • 68 Views
  • Uploaded on

Flux studies in contrasting environments (obj. 2) The role of heterotrophy (bact. microzoo). Specific objectives. Quantification of the carbon flux exported – Obj. 2.2-. What is the impact of natural iron fertilization - On the structure of the microbial food web

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Flux studies in contrasting environments (obj. 2) The role of heterotrophy (bact. microzoo)' - emile


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Flux studies in contrasting environments (obj. 2)

The role of heterotrophy (bact. microzoo)


Specific objectives

Quantification of the carbon flux exported – Obj. 2.2-

  • 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


? IRON ?

? ? ? ? ? ? ? ?? ? ?? ? ?? ? ?? ?

O2

CO2

nanoflagellates

copepods

ciliates

Gross Community

production GCP

and Dark Community

Respiration DCR

DOC

heterotrophic

bacteria

picophytoplankton

nanophytoplankton

CO2

O2

microphytoplankton

P, N

Silicates


O2

CO2

nanoflagellates

copepods

ciliates

Gross Community

production GCP

and Dark Community

Respiration DCR

DOC

heterotrophic

bacteria

picophytoplankton

nanophytoplankton

CO2

O2

microphytoplankton

P, N

+ iron

Silicates

Is there changes in bacterial biomass, ectoenzymatic activities,

production, respiration ?


Indirect effects of IRON on microbial food web

1. Is the response of the microbial food web a cascade effect from

Phytoplankton stimulation?

O2

CO2

nanoflagellates

copepods

ciliates

Gross Community

production GCP

and Dark Community

Respiration DCR

?

grazing ?

sinking ?

DOC

heterotrophic

bacteria

picophytoplankton

nanophytoplankton

?

CO2

O2

microphytoplankton

P, N

+ Fe

Silicates

What is the fate of the phytoplankton ?

Phytoplankton growth  phytoplankton grazing rates, abundance of predators, relations between predators?


Heterotrophy and remineralisation

Indirect effects of IRON on microbial food web:

2. Do bacteria benefit from the carbon derived from Fe stimulated primary production?

O2

CO2

nanoflagellates

copepods

ciliates

Gross Community

production GCP

and Dark Community

Respiration DCR

DOC

heterotrophic

bacteria

picophytoplankton

nanophytoplankton

CO2

O2

microphytoplankton

nutrients

Silicates

Does the Fe fertilization influence

- the production and respiration of bacterioplankton and consequently theBGE ?

- the factors limiting bacterial activity (Fe vs DOC)


Tools for studying biomasses

1. Structure of the food web in terms of stocks

  • 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 fluxes

2. Fluxes

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 fluxes

Use of fluorescent labelled preys

Fluorescent labelled bacteria for bacterial grazing by flagellates

Fluorescent labelled algae for grazing of nanophytoplankton by ciliates.


Tools for studying fluxes

Grazing of pico and nano

autotrophs by ciliates

FLS

FLS (fluorescently labelled

Synechococcus)

Synechococcus analog

FLA

Nanochloropsis sp. (2-4 μm)

FLA (fluorescently labelled algae,

Rublee & Gallegos 1989)

Nanophytoplankton analog


Sampling strategy

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

A5

D1

M2

D2

D3

D4

D5

D6


  • In situ

  • Profiles : standing stocks and BP, O2/CO2 fluxes

  • Surface 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 ml

  • O2/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 experiments

  • Response 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 ?


ad