Download Dissolved Organic Matter- what is inside the black box? - C-MORE

Dissolved Organic Matter- what is inside
the black box?
What is the relationship between organic matter
composition, microbial diversity & production?
How is microbial metabolism coupled to organic matter
structure?
How does DOM affect microbial adaptation & evolution?
What sets the ocean inventory of organic carbon,
and why is so much organic carbon preserved in seawater?
Why do organic nitrogen and phosphorus accumulate
in nutrient limited regions of the surface ocean where they
are most needed, but disappear in the mesopelagic ocean
where they are not needed?
DOC sampling is hard to do…
Isolation of DOM by ultrafiltration
Separation based on size
1 nm pore @ 1 kD
Selects for HMW fraction
about 30-35% TOC
Membrane effects what
Is collected
Some salts collected too!
DOC sampling
filter (1 nm)
sample concentrate
(> 1000 MW)
pump
filtrate
(< 1000 MW)
>1000 D
DOM fraction
30-35% DOC
membrane filter
Ultrafiltration high molecular weight DOM (HMWDOM)
< 1000 D
DOM fraction
65-70% DOC
Final product
30-35% of total DOC
DOM analysis by Nuclear Magnetic Resonance spectroscopy
13C
Nuclear Magnetic Resonance Spectrum
of high molecular weight dissolved organic matter (HMWDOM)
Abundance
Frequency
13C
Nuclear Magnetic Resonance Spectrum
of high molecular weight dissolved organic matter (HMWDOM)
Frequency
Abundance
Different types of carbon
resonate at different
frequencies
Area is proportional to the
amount of carbon
200
150
100
50
0 ppm
1H, 31P, 15N
- NMR spectra of HMWDOM
1H
15N
31P
Clark et al L&O 2001
13CNMR
spectra of HMWDOM
from the Atlantic and Pacific
Sargasso Sea
3m
NPSG
3m
13CNMR
of marine phytoplankton*
Fragilariopsis cylindrus
Phaeocystis antarctica
*Adina Paytan, 2005
13CNMR
of plankton tows
Hedges et al GCA 2001
13CNMR
of HMWDOM in different
aquatic environments
North Pacific Ocean
Great Salt Lake
Leenher et al., (2004) Biogeochem. 69, 125-141
Andrews Creek, RMNP
McKnight et al. (1997) Biogeochem. 62, 99-124
HMWDOM in the deep sea
Sargasso Sea
NPSG
3m
3m
2500 m
1800 m
13C
Nuclear Magnetic Resonance Spectrum
of high molecular weight dissolved organic matter
13C
Nuclear Magnetic Resonance Spectrum
of high molecular weight dissolved organic matter
COOH
CONH
(10%)
13C
Nuclear Magnetic Resonance Spectrum
of high molecular weight dissolved organic matter
OCO
(12%)
COOH
CONH
(10%)
13C
Nuclear Magnetic Resonance Spectrum
of high molecular weight dissolved organic matter
OCO
(12%)
COOH
CONH
(10%)
HCOH
(55%)
13C
Nuclear Magnetic Resonance Spectrum
of high molecular weight dissolved organic matter
C/N = 15 +/- 3
COOH
CONH
(10%)
OCO
(12%)
HCOH
(55%)
CHx
(10%)
13C
Nuclear Magnetic Resonance Spectrum
of high molecular weight dissolved organic matter
C/N = 15 +/-3
COOH
CONH
(10%)
OCO
(12%)
HCOH
(55%)
CHx
(10%)
HCOH = 4-5
OCO
HMWDOC, what could it be?
From our knowledge of cell biochemicals…
Proteins
C/N = 4,
CHx(O):CON =
3
Carbohydrates
C maybe N HCOH:OCO =
5
Lipids
C only
CHx:COOH = 18
CHx:COH = 30
HMWDOC, what could it be?
From our knowledge of cell biochemicals…
Proteins
C/N = 4,
CHx(O):CON =
3
Carbohydrates
C maybe N HCOH:OCO =
5
Lipids
C only
CHx:COOH = 18
CHx:COH = 30
……..looks to be mostly (50-70%) carbohydrate !
Spectral and chemical analyses of HMWDOC
Carbohydrate
50-70% of HMWDOC
-O13CNMR
Acid
hydrolysis
200
150
100
50
0
-O-
Spectral and chemical analyses of HMWDOC
Acid hydrolysis followed by
Monosaccharide analyses
yields 7 major neutral sugars
that represent 10-20% of HMWDOC
in surface water
Carbohydrate
50-70% of HMWDOC
13CNMR
Acid
hydrolysis
R F A X Gl M Ga
200
150
100
50
0
NMR and carbohydrate analyses of deep sea HMWDOC
monosaccharide distribution
relative %
surface
relative %
deep
“nonreactive” DOC
14C = DOC(deep)
Can we use the 14C of pure sugars to determine
If they are part of the reactive or nonreactive fraction of DOC?
reactive DOC
14C=DIC
Radiocarbon analyses of HMWDOC carbohydrates
Sample
Hawaii
NPSG
DIC
72+7‰ (n=4)
89+7‰*
Glucose
Galactose
Mannose
Xylose
Arabinose
Fucose
Rhamnose
47, 58
67
65
52, 58
63
49, 52
40, 57
79
103
99
94
ND
69
57
Average
56+6‰
89+13‰
*data from Ellen Druffel
Can 14C in sugars constrain the turnover time of
The “semi-reactive” fraction of DOC?
Assume the concentration of reactive DOC is at steady state,and that it produced
each year with a 14C value equal to DIC. Each year a fraction of the sugars
radiocarbon
are non-selectively removed and the 14
C value formodel
the remainder is calculated.
200
del14C values
150
100
50
DIC
1 year
2 years
0
3.3 years
10 years
-50
-100
1952
1962
1972
1982
year
1992
2002
What else is in HMWDOC ?
15N
NMR
(90-98%)
Amide-N
=
O
-C-N
Amino-N
-C-NH2
(2-10%)
What else is in HMWDOC ?
15N
NMR
proteins
Amide-N
Amino-N
-C-N-
-C-N-
O
O
amino sugars
CH3CONH
CH3CONH
Is a large fraction of HMWDOC and HMWDON
from amino sugars?
15N
Amide-N
NMR
1HNMR
Acetate
Is a large fraction of HMWDOC and HMWDON
from amino sugars?
15N
1HNMR
NMR
Amide-N
Acetate
HNOCCH3
HNOCCH3
Is a large fraction of HMWDOC and HMWDON
from amino sugars?
Amide-N
HNOCCH3
HNOCCH3
Amino-N
HNH
HNH
Is a large fraction of HMWDOC and HMWDON
from amino sugars?
15N
1H
CH3CONH
CH3CONH
acid
HNH
HNH
+
CH3COOH
Composition and cycling of HMWDOM
Surface HMWDOM
Most of the carbon (75%) is
carbohydrate
Half the N is from aminosugars,
about 10% is from proteins
The sugar/aminosugar fraction
is the “semi-labile: DOC that
accumulates in surface water
this may fuel about 50% of
microbial production in surface
waters.
Why does it accumulate?
What is the composition of
Non-reactive DOC in the deep ocean
(1800 m Pacific)
Non-reactive DOM
Semi-reactive DOM
Very reactive DOM
-C-N-
HO
-C-NO
O
-C-N-
-C-N-
O
O
O
-C-NO
-C-NCH3
CH2 CH2
O
Mostly polysaccharides
Don’t really
Know
Humic substances?
Biopolymers…
80-90% of cell C-N-P
Free amino acids
Simple sugars
Urea…etc.
10-20% of cell C-N-P
Non-reactive DOM
Humic substances
Concentration = 40 µM
Inventory = 650 GT C
14C= -400 to -600‰
Annual flux = 0.1 GTC
Semi-reactive DOM
Proteins
Polysaccharides
Biopolymers…
80-90% of cell C-N-P
Very reactive DOM
Free amino acids
Simple sugars
Urea…etc.
10-20% of cell C-N-P
25-40 µM
100 nm-1µM (?)
30-50 GT C
0.1- 1 GT C
14C= +70-90‰ (?)
Moderate to large ?
14C= +70-90‰
Large