1. Dissolved Organic Carbon, Nitrogen, and Phosphorous in seawater
Fuels the microbial loop
Sequesters a large amount of carbon,
as well as nitrogen and phosphorus
Complexes trace metals and affects their
concentration and bioavailability
Absorbs UV and PA radiation

2. Reactivity and the cycling of DOC in seawater
Semi-reactive DOC
Nonreactive DOC
Very reactive DOC
Heterotrophic microbial production ??
0o and 140 oW
Carlson and Ducklow, DSR II v 42;

3. Reactivity and the cycling of DOC in seawater
High production in the surface
(high microbial activity & production)
It’s all
Semi-reactive DOC
Low production in the deep
(low microbial activity & production)
Carlson and Ducklow, DSR II v 42;

4. Deep sea gradients in [DOC]
D. Hansell and C. Carlson, Nature 1998

5. Deep sea gradients in [DOC]
D. Hansell and C. Carlson, Nature 1998
Unpublished data
removed
AAIW
NADW
AABW

8. History of radiocarbon in the
Atmosphere and ocean
Frigate shoals
Figi
14C per mil
Galapagos
Prebomb value of -80 per mil

9. DOC cycling via DO14C UV photooxidation HCO3- + H+ H2O + CO2 1000L
Williams, Oeschger, and Kinney; Nature v224 (1969)
UV photooxidation
1000L
HCO3- + H H2O + CO2

10. DOC cycling via DO14C UV photooxidation 1000L Depth 14C(‰) Age
Williams, Oeschger, and Kinney; Nature v224 (1969)
UV photooxidation
1000L
1880m ‰ ybp
1920m ‰ ybp
Depth 14C(‰) Age

11. How do we measure radiocarbon today ?
LN2 trap
For CO2
Reduce to graphite
mls
press into a target
Mass spectrometer
Analysis
(>25 µg C needed)

12. Accelerator Mass Spectrometry (AMS)
NOSAMS at Woods Hole
Just like we can now do DOC measurements on small samples of seawater with very high precision, we can also do AMS on small samples with high precision- although it is very expensive.
C-14 PP measurements use 106x more C-14 than natural abundance!!!!!

13. Radiocarbon in the Atlantic and Pacific Oceans
Peter M. Williams and Ellen Druffel; Nature 1987, JGR 1992
AMS technologu came along in the late 1970s, (old accelerators being replaced but looking for new business)m they allowed for an expansion in the number of samples processed. You don’t need 1000L anymore. So Pete along with graduate student Ellen Druffel at SIO began to generate full water column profiles of DO14C.
Suzuki issue

14. Radiocarbon in the Atlantic and Pacific Oceans
DIC 14C in surface waters
of the Atlantic and Pacific
has the same isotopic value.

15. Radiocarbon in the Atlantic and Pacific Oceans
DIC 14C in surface waters
of the Atlantic and Pacific
has the same isotopic value.
The deep Pacific DIC is older
than the deep Atlantic DIC

16. Radiocarbon in the Atlantic and Pacific Oceans
DIC 14C in surface waters
of the Atlantic and Pacific
has the same isotopic value.
DOC is always older than DIC
(by 4 kyrs in surface water)
DIC-> POC -> DOC

17. Radiocarbon in the Atlantic and Pacific Oceans
DIC 14C in surface waters
of the Atlantic and Pacific
has the same isotopic value.
DOC is always older than DIC
by 4 kyrs in surface water
14C of DIC and DOC
is about the same in the
deep Atlantic and Pacific

18. Radiocarbon in the Atlantic and Pacific Oceans
DIC 14C in surface waters
of the Atlantic and Pacific
has the same isotopic value.
DOC is older than DIC
by 4 kyrs in surface water
14C of DIC and DOC
is about the same in the
deep Atlantic and Pacific
Deep ocean values of DOC
are equal to a radiocarbon
age of yrs
Either there is a source of
“old” DOC, or DOC persists
for several ocean mixing
cycles

19. Why is DOC so old (2000 ybp) in surface water?
DIC

20. “DOC Background” Why is DOC so old (2000 ybp) in surface water?
Pete Williams and Ellen Druffel

21. Why is DOC old in surface water?
reactive DOC
14C=DIC
“nonreactive” DOC
14C = DOC(deep)
14C= 14C“reactive” DOC + “nonreactive” DOC

22. Using a simple 2 component mixing model of old “non-reactive” DOC
with deep sea 14C and [DOC] values, and a new “reactive” component with
DIC 14C, and [DOC] = [DOC]total-[DOC]deep,
[DOC]total  14C total = [DOC]deep  14C deep + [DOC]new  14C new
DOC 14C
DOC 14C
Depth

23. Using a simple 2 component mixing model of old “non-reactive” DOC
with deep sea 14C and [DOC] values, and a new “reactive” component with
DIC 14C, and [DOC] = [DOC]total-[DOC]deep,
[DOC]total  14C total = [DOC]deep  14C deep + [DOC]new  14C new
DOC 14C
DOC 14C
Modeled and measured DOC 14C values agree pretty well…
Depth

24. 14C= “reactive” DOC + “nonreactive” DOC
Atlantic surface water
14Ccalc = ‰
14Cobs = ‰
Pacific surface water
14Ccalc = ‰
14Cobs = ‰
reactive DOC
14C=DIC
nonreactive DOC
14C = DOC(deep)
Everyone believes this, but it is weird bc it implies that either there is incredible consisitency in the ocean or there are only two pools of carbon
Nonreactive DOC = 650 GT C
Reactive DOC = GT C

25. What flux of carbon is needed to maintain the
“old” marine DOC reservoir?
Global inventory/residence time = annual flux
680 GT C/ yr = GT C/yr !!!
How does this compare with other C fluxes?

26. Where does doc come from? DOC and major carbon reservoirs and fluxes
Terrestrial Plants
900 GT C
Atmosphere 750 GT (CO2)
Terrestrial Primary
Production 75 GT C/yr
Marine Primary
Production GT C/yr
River flux
0.5 GT C/yr
Soil 2000 GT C
POC 15 GT C
Burial
GT C/yr
DOC 700 GT C
Carbonates 60,000,000 GT C
Kerogen ,000,000 GT C
150 GT C

27. The ocean, a global carbon wastebasket?
A small fraction of the DOC added to the ocean by rivers is colored (colored dissolved organic matter or CDOM) that can be tracked by remote sensing. It is believed that river DOM is remnant of OM cycling on land, and represents the material that cannot be degraded. Is the ocean filling up with terrestrial DOM?

28. DOC transport through estuaries and the input of
terrestrial organic carbon to the ocean.
DOC concentrations are nearly always
higher in rivers than in the ocean. Rivers
add C to the ocean.
In general, DOC displays conservative
behavior wrt salinity in estuaries.
Some estuaries add carbon, some
remove it.
Salinity (ppt)

29. Utilization of DOM by bacteria at different salinities
in the York River
Raymond and Bauer AME v 22 (2000)

30. What is the source of oceanic DOC ?
Druffel et al., JGR 1992
Stable C isotopes
Marine C
-21‰
Terrestrial C
C3 plants -27‰
C4 plants -15‰

31. Production of reactive and non reactive DOC by
phytoplankton and bacteria
Microbial diversity is due to
Changes in very reactive DOC
CO2
Reactive DOC O2
Non reactive DOC ?
Very reactive DOC
Bacterial production is thought to be fuelled by very reactive DOC (simple, LMW organic compounds) that have half lives in seawater of hours to days.

32. ….then why isn’t the ocean filled with river DOC,
and where does the non reactive marine DOM come from?

33. Data from Bob Chen and Jeff Bada
DOC (µM)
Data from Bob Chen and Jeff Bada

34. Ken Mopper and his group fwere able to show rapid photoxidation
Of DOM in the presence of sunlight
Filtered SW
DOC + light LMW carbonyls (C=O)
C=O + fluorophore HPLC
Whole SW
Filtered SW
The answer has its origins in marine microbiology
Whole SW
Not produced in dark controls,but are produced in sterile controls

35. Production of LMW highly oxidized DOC with depth in the ocean
DOC + light LMW photo-oxidation products
Is photochemical degradation the long term sink for river (terrestrial)
And therefore nonreactive DOM in the ocean ???

36. H2C=O
HOOCCOOH

37. CH3C=O CH3(C=O)CH3 CH3CH2CH2OH
Highly oxidized LMW compounds are produced every
day in seawater by photo-oxidation. They serve as a substrate
for bacteria and therefore a sink for non-reactive DOC
CH3C=O
CH3(C=O)CH3
Paradox here, in that if photoxidation is the sink for DOM, then 20-25% of it should be destryed, and fairly fairly rapidly when it reaches the surface. This would mean a loss of 8-10 um or the 40 um DOC of the old DOC. So why does the 14C model then balance?
CH3CH2CH2OH

38. Unpublished data removed
…..then why is the ocean filled with (40 µM) marine DOC, and where does it go?
Unpublished data removed
Which brings us to deep sea losses in DOC- the RC age implies that it is very hard to metabolize. But not impossible perhaps? There are deep sea gradients in DOC

39. Dissolved organic nitrogen and phosphorous
Organic C-N-P are connected at the molecular level;
what is true for C is (assumed to be) true for N and P.
We cannot determine the age of DON directly. DOP
residence times in surface water can be measured using
cosmogenic 33P/32P.
DON and DOP concentrations are higher in surface waters
(where production > degradation), than in the deep sea,
so we infer from DOC/DON/DOP ratios that there
are “nonreactive” and “reactive” fractions of DON and DOP.
DON and DOP are even more difficult to measure than DOC,
there is no way to remove inorganic N and P from seawater
prior to DON/DOP analyses, so all measurements of organic N/P
are difference measurements.

40. What drives microbial diversity in the ocean ?
Karner et al. Nature 2001

41. 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?
Karner et al. Nature 2001