SS3.04 Biogeochemistry of DOC/DON in a Watershed Context
Date: Wednesday, June 12, 2002
Time: 4:45:00 PM
Location: Carson B
 
DittmarT, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, tdittmar@awi-bremerhaven.de
Kattner, G, , Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, gkattner@awi-bremerhaven.de
 
BIOGEOCHEMICAL CHARACTERISTICS OF TERRESTRIAL VERSUS MARINE-DERIVED DISSOLVED ORGANIC MATTER IN THE ARCTIC OCEAN
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For studying the fate of terrestrial dissolved organic matter (DOM) in the ocean the Arctic provides a model system, because of the large freshwater input and conservative mixing of DOM. We chemically characterised DOM from the Russian rivers into the Arctic Ocean on molecular level and by liquid chromatography with high-sensitive organic carbon detection. Riverine humics exhibited a complex and aromatic structure, whereas diagenetically mature DOC in the deep sea was composed to about 40% of aliphatic and very small (<300 g/mol) neutral molecules, largely with amphiphilic character. On molecular level <10% of DOM could be characterised as carbohydrate and amino acid moieties in the rivers and only <4% in the deep sea. Microbial-derived D-amino acids contributed significantly more to oceanic then to riverine DOM. In riverine DOM D-aspartic acid was most abundant (21% of total aspartic acid) and in deep seawater D-alanine predominated (44% of total alanine). The major part of marine DOM has surprisingly different chemical structures and physico-chemical features than previously thought, and terrestrial diagenesis is much more efficient in protecting amino acids from bacterial degradation than marine diagenesis.