2. Rainer M.W. Amon1, Benedikt Meon2
Missing organic carbon in the coastal Kara Sea – Is coastal erosion a significant source?
Rainer M.W. Amon1, Benedikt Meon2
1Texas A&M University at Galveston, Dept. of Marine Sciences and Oceanography, Galveston, USA
2Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

3. East Siberian Sea
Laptev Sea
Yenisei
Kara Sea OB
Barents Sea

4. Why are we interested in terrestrially- and permafrost-derived organic matter in the Arctic Coastal Ocean ?
The role of terrestrially-derived organic matter as a carbon and nutrient source for the Arctic Ocean food web.
The use of terrestrial organic matter as a tracer for water mass dynamics and environmental change in the Arctic Ocean.

5. DISTRIBUTION OF DOC ALONG THE SALINITY GRADIENT
BP 99 Ob
(08/24-09/07 )
y = -12,2x + 597 R 2
= 0,865
100
200
300
400
500
600
700
800 5 10 15 20 25 30 35
DOC [µM C ]
BP 99 Yen
(08/26-09/06)
y = -18,5x + 740 R 2
= 0,949
100
200
300
400
500
600
700
800 5 10 15 20 25 30 35
BP 00 Ob
(09/03-09/21)
y = -16,4x + 617 R 2
= 0,903
100
200
300
400
500
600
700
800 5 10 15 20 25 30 35
salinity [psu]
DOC [µM C ]
BP 00 Yen
(09/06-09/19)
y = -18,3x + 679 R 2
= 0,948
100
200
300
400
500
600
700
800 5 10 15 20 25 30 35
salinity [psu]

6. RIVER DOM LOSSES ON THE SHELFA
100
200
300
400
500
600
700 5 10 15 20 25 30 35
salinity [psu] 40
DOC [µM C]
POC [µM C]
DOC (µM)
POC (µM)
Flocculation experiment:<5% losses
Time [d] 2 4 6 8
600
DOC [µM]
500
550
650
700
750
Bacterial decomposition experiment: <5% losses

7. TERRESTRIAL-DOM EXPORT FROM THE ARCTIC OCEAN
Amon et al. 2003

8. Bacterial activity and DOM
350
300
Surface
y = 38.18x
300
Pycnocline
250
r = 0.78
p < 0.001
250
Close to bottom
200
Leucine inc. (pM h-1)
200
Leucine inc. (pM h-1)
150
150
100
100 50 50 Ob
Yenisei
Estuary
Kara Sea 1 2 3 4 5
(5-15 psu)
(>20 psu)
Chl a (µg l-1)
0.3
0.25
0.2
Tg C per day ?
0.15
0.1
0.05
Bacterial carbon demand
Primary production
River input

9. DISTRIBUTION OF TERRESTRIAL-DERIVED DOM IN THE ARCTIC OCEAN
-28
No sign of increased concentrations of terrestrial DOM in the deep Fram Strait and the deep central Arctic Ocean.
Unpublished data from the Laptev Sea slope and the Mendeleev Ridge indicate vertical transport of terrestrial DOM to at least 1600 m.
These observations might suggest a change in deep water formation patterns over the last decade in the Arctic Ocean.
rivers
EGC
-26
Atlantic water
PDW
GIN Sea
-24
 13C
PSW
-22
-20 10
100
1000
10000
100000
Lignin phenols (ng/l) 5 10 15 20 25 30 35
% TDOC
Arctic SW (≤55m)
Arctic DW (≥1000m)
Arctic IMW (60-600m)

10. COMPOSITION OF RIVER UDOM
Ob 97
Ob 99
Yenisei 97
Yenisei 99
C/N
43.5
39.8
48.1
42.3 δ
13C
-27.6
-27.7
-27.1
15N
2.5
2.8
1.9
2.6
Δ14C 84
307
150
108
lignin
23.5
24.7 33 50
NS yield
3.1
4.1
1.8 2
Is DO14C a valuable tracer for the mobilization of Permafrost organic matter in the Arctic Ocean?

11. COMPOSITION OF MOLECULAR WEIGHT FRACTIONS
Size fractions
Neutral sugars (%OC) 10 15 20 25 30 35 40 45 50
-29
-28
-27
-26
-25
-24
Total UDOM
> 100 kDa
kDa
kDa
C/N
13C

12. CONCLUSIONS
Carbon metabolism studies in the Kara Sea demonstrate our poor understanding of carbon sources and sinks on Arctic Shelves – costal erosion has not been considered as a carbon and nutrient source yet.
In general, terrestrially-derived DOM from major Siberian Rivers appears conservative providing a potential tracer for water mass dynamics and environmental change for Arctic shelves and the central Arctic Ocean, at least on a 2-6 year time scale. The Eurasian and Canadian Arctic might differ.
DO14C values of Siberian River DOM appear modern suggesting that at the moment there is no mobilization of old permafrost organic matter into the river DOM pool, however, partitioning and bioavailability of permafrost organic matter needs to be determined.
There is some evidence that the incorporation of terrestrial-derived DOM into Arctic Ocean deep water might have changed over the last decade.

13. ACKNOWLEDGEMENTS
Captain, scientists, and crew of Polarstern, Akademik Boris Petrov, USS Pogy, USS Archerfish, USS Hawkbill
Ron Benner University of South Carolina;
Funding: German Federal Ministry for Education and Research, European Community (COMET), DAAD (German Academic Exchange Service), US National Science Foundation

14. RELATIONSHIP BETWEEN FLUORESCENCE (350-460/550NM),
RIVERINE DOM AND LIGNIN PHENOL CONCENTRATIONS
y = x R 2
= 0.999
0.5 1
1.5
2.5 3
3.5 4 5 10 15 20 25 30
% river Water
y = x = 50
100
150
200
250
300
350
400
450
500
0.3
0.35
0.4
0.45
0.55
0.6
Fluorescence ( /550nm)
Fluorescence (V)
LOP (µg/l)
Amon et al. 2003

15. BIOLOGICAL AND PHYSICAL PROCESSES ON ARCTIC SHELVES
30 psu surface salinity psu
~100 µM surface DOC ~700 µM
River runoff
sea ice formation PP PP PP
Brine release: enrichment of salt and DOM
export
mixing
bacterial DOM utilization
Nutrient regeneration
Modified shelf water