Missing organic carbon in the coastal Kara Sea – Is coastal erosion a significant source?

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

6. 700 40 A 600 30 500 DOC (µM) 400 POC (µM) 20 300 200 10 DOC [µM C] 100 POC [µM C] 0 0 0 5 10 15 20 25 30 35 salinity [psu] 750 700 DOC [µM] 650 600 550 500 0 2 4 6 8 600 Time [d] RIVER DOM LOSSES ON THE SHELF Flocculation experiment:<5% losses Bacterial decomposition experiment: <5% losses

7. TERRESTRIAL-DOM EXPORT FROM THE ARCTIC OCEAN 79°N 71°N 67°N 75°N Amon et al. 2003

8. Bacterial activity and DOM 300 350 Surface y = 38.18x + 37.191 300 r = 0.78 250 Pycnocline p < 0.001 Closeto bottom 250 200 Leucine inc. (pM h-1) Leucine inc. (pM h-1) 200 150 150 100 100 50 50 0 0 Ob Yenisei Estuary Kara Sea 0 1 2 3 4 5 Chl a (µg l-1) (5-15 psu) (>20 psu) 0.3 0.25 0.2 ? Tg C per day 0.15 0.1 0.05 0 Primary production River input Bacterial carbon demand

9. 35 30 25 20 15 10 5 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 Unpublished data from the Laptev Sea slope and the Mendeleev Ridge indicate vertical transport of terrestrial DOM to at least 1600 m. These observations might suggest a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) % TDOC 0 Arctic SW (≤55m) Arctic DW (≥1000m) Arctic IMW (60-600m)

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

11. 50 Total UDOM 45 > 100 kDa 30 - 100 kDa 40 1 - 30 kDa 35 30 Neutral sugars (%OC) 25 20 15 10 Size fractions -24 -25 -26 -27 -28 -29 COMPOSITION OF MOLECULAR WEIGHT FRACTIONS 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 ScienceFoundation

14. 4 500 y = 2350.7x - 853.56 450 3.5 2 R = 0.9046 400 3 350 2.5 300 Fluorescence (V) LOP (µg/l) 2 250 200 1.5 y = 0.1218x + 0.3786 150 R 2 = 0.999 1 100 0.5 50 0 0 0 5 10 15 20 25 30 0.3 0.35 0.4 0.45 0.5 0.55 0.6 % river Water Fluorescence (350-460/550nm) RELATIONSHIP BETWEEN FLUORESCENCE (350-460/550NM), RIVERINE DOM AND LIGNIN PHENOL CONCENTRATIONS Amon et al. 2003

15. BIOLOGICAL AND PHYSICAL PROCESSES ON ARCTIC SHELVES 30 psu ------------------------- surface salinity ------------------------------- 0 psu ~100 µM ------------------------ surface DOC ----------------------------- ~700 µM River runoff PP sea ice formation PP PP Brine release: enrichment of salt and DOM export mixing bacterial DOM utilization Nutrient regeneration Modified shelf water