RECIPE meeting May 17-20 Th Munich,GERMANY « Earth Science Institute of Orleans », France Group « Organic Matter in water, sols, sediments and rocks » Laure Comont, Fatima Laggoun-Défarge, Jean-Robert Disnar Pascale Gautret, Nathalie Lottier, Marielle Hatton, Li Huang
RECIPE meeting May 17-20 Th Munich,GERMANY. Laure Comont, Fatima Laggoun-Défarge, Jean-Robert Disnar Pascale Gautret, Nathalie Lottier, Marielle Hatton, Li Huang. « Earth Science Institute of Orleans », France Group « Organic Matter in water, sols, sediments and rocks ». - PowerPoint PPT Presentation
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RECIPE meeting
May 17-20Th Munich,GERMANY
« Earth Science Institute of Orleans », FranceGroup « Organic Matter in water, sols, sediments and
Pascale Gautret, Nathalie Lottier, Marielle Hatton, Li Huang
Munich progress meeting May 17-20th
WP5 work progress since Carentan meeting
II- Sugar analyses on the bulk peat compared to the fine-grained fraction(Le Russey sites on FRC & FRD) => identification of biomarkers (OM degradation processes)III- Tests of aminoacid analyses on 2 samples from CH (solid and soluble fractions) :=> interesting preliminary results obtained for identification of neoformation markers=> results are correlated with cryo-scanning electron microscopy (cryo-SEM) observations
IV – Microtexture of peat (2 distinct scales): cryo-SEM X-ray computed tomography
I – Exploration of physico-chemical data (PCA) on peat OM from the five studied sites (WP01) (correlations between C, N, organic constituent
countings; sugar analyses in both bulk peat and fine-grained fraction)
I – DETERMINATION OF
VARIOUS CORRELATIONS
Munich progress meeting May 17-20th
Munich progress meeting May 17-20th
Principal component analyses (PCA)
CH : 1963 (~40 yrs) and FR : 1984 (~20 yrs)FB (less than 5 yrs ?)
Test of identification of total aminoacids: La Chaux d’Abel,fen situation CHA
peat profil
Soluble fraction, ultrafiltration: fraction (>3kDa) F1
fraction (<3kDa) F2
Solid bulk peat
Soluble fraction, ultrafiltration: fraction (>3kDa) F1
fraction (<3kDa) F2
Solid bulk peat
3kDa ~ 400Å
Chaux d’Abel, CHA situation, aminoacid results
Munich progress meeting May 17-20th
- 2 compartments: soluble and solid fractions
In soluble fraction: high % of basic AA (Lys & Arg) ➱ Preferential accumulation of basic AA in acidic environment ?
➱ Another source (microorg. groups rich in basic AA)?
-Gly: smallest and simplest AA=> index of degradation
living plants
peatsoluble OM
Munich progress meeting May 17-20th
Chaux d’Abel, CHA situation, aminoacid resultsSolid bulk
Solid fraction:All AA are well represented including
di-carboxylic AA (Asp, Glu..)
soluble (> 3kDa)
Soluble fraction:mainly composed of basic AA (Arg & Lys)+ Free ammonia => degradation markers
soluble (< 3kDa)
Example: chrommatogram of level 4 (5-10 cm)
Non proteinic AA (Orn & unknown peaks)=> neosynthetic AA from abiotic or biotic
activity
?
?
?
?
? ?
=> 2 hypotheses - important and widespread microbial population (either active or dead) ? to be correlated with microbial groups WP03
- selective preservation of some plant proteins and accumulation due to specific environmental conditions ?
Chaux d’Abel, CHA situation, aminoacid results
Munich progress meeting May 17-20th
At 5-10 cm (regenerated peat): high diminution of total AA compared to living plants => degradation of plant proteins in this level. That’s confirmed by the total AA quantity in soluble fraction.
At 35 cm (old peat): amounts of AA are 20 times higher than those at the surface and also higher than those of living plants.
=> 20% of Gly
96% of free NH3 42% of Gly
Hydrolysable AA YIELD (mg/g) or (mg/l)
Frequency histograms of individual AA examplify these correlations
Munich progress meeting May 17-20th
Chaux d’Abel, CHA situation, aminoacid results
Good correlation between peat samplesand some living plants
Microbial production or selective preservation ?
Chaux d’Abel, sugar results on soluble fraction
Munich progress meeting May 17-20th
level 4 (5-10 cm) level 7 (32,5-37,5 cm)
Total sugar contents ≈ 5,5 mg/l 58% of unknowns (neoformed ?)
Total sugar contents ≈ 8,3 mg/l 23% of unknowns (neoformed ?)
Higher Total sugar contents in the soluble fraction at depth than at the sub-surface (level 7 vs. 4) are these soluble compounds autochthonous or not (i.e. brought by diffusion from the surface or elsewhere);
Microbial production or selective preservation ?
Higher proportions of xylose (glucose?) and fucose at depth => inheritance (xylose?) and/or in situ microbial production (fucose?)?
Munich progress meeting May 17-20th
Cryo-scanning electron microscope (cryo-SEM)
The cryo-SEM is equipped with a freeze-drying sample preparation system.
It allows studing the composition and the micromorphology of hydrous materiel (peat) and spatial relationships between organic components.
FRC, 2nd regeneration stage
level 3 (0-5 cm)
level 5 (12,5 - 17,5 cm)
level 8 (42,5 - 47,5 cm)
Tests were carried out on samples from Le Russey site:
Microbial production or selective preservation ?
The cryo-SEM, results, FRC 2nd regeneration stage
level 3
Microbial production or selective preservation ?
3D polysaccharidic networkCross section of Sphagna steam
Microorganisms inside well-preserved cell walls
level 5
BiofilmEps(extracellular polymer secretion)
level 8
3D polysaccharidic network
degraded cell walls
Bacterial colony
50µm 12µm 2,3µm
5µm 3µm 3µm
Munich progress meeting May 17-20th
Preliminary conclusions
distinct degradation processes between these 2 peat samples:
Solid fraction Soluble fraction
Total AA ≈ 5 µg/mg Total AA ≈ 43,51µg/ml
Total sugars ≈ 5.5 mg/l
level 4 : - High living plant proteinsdegradation in the solid fraction
- High sugars degradation in soluble fraction
Solid fraction Soluble fraction
Total AA ≈ 13,14 µg/ml
Total sugars ≈ 8,3 mg/l
Total AA ≈ 134 µg/mg
level 7 : - High hydrolysable AA yield
in the solid fraction ≠ materiel sources lower degradation
- Higher Tot. sugar contents in the soluble fraction
2 processes are determined : - Selective preservation - Microbial production
Which of these 2 processes is dominant ?
IV – PHYSICAL MICROTEXTURE
OF THE PEAT
Munich progress meeting May 17-20th
FRA, bare peat
level 3 (0-5 cm)
FRC, 2nd regeneration stage
level 3 (0-5 cm)
level 5 (12,5 - 17,5 cm)
level 8 (42,5 - 47,5 cm)
Munich progress meeting May 17-20th
Physical microtexture of the peat
I- Cryo-SEM observations:
bare peat, FRA 2nd reg. stage, FRC
more compact, dense peat
analyses are in progress
distinct µmorphologies in the bare peat & the transition « old »/« new » peat
II- X-ray computed Tomography :
Tests carried out on 2 samples (Coll. R. Swennen from Leuven University, Belgium):RyI = FRC level 7-12 cm RyI = FRC level 40-50 cm
Visualisation of the 3D porous network on different peattypes under increasing range of wetness (re-wetting process)
level 3 level 5
5µm 5µm
Munich progress meeting May 17-20th
Conclusions
- Association of AA analyses + sugar analyses in soluble fraction
=> interesting approach to better identify the markers of OM degradation
to be applied in WPO2…- Exploration of physico-chemical data (PCA) on peat OM from the five sites (WP01)
=> distinct evolution trends for Jura peatlands and SC/FI peatlands => climatic influence ? Initial
vegetation types ?
-2 important problems arise:
=> datations of both «new» peat horizons and transitional peat layer
=> insufficient numbers of peat samples along the profiles of the new regenerating horizon (only 2 to 3)
For WPO2 => adopt a better strategy of sampling !!!!!