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Evidence for terrigenous dissolved organic nitrogen in the Arctic deep-sea

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Citation:
Dittmar, T. (2004): Evidence for terrigenous dissolved organic nitrogen in the Arctic deep-sea , Limnology and oceanography, 49 (1), pp. 148-156 .
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Abstract:

In order to trace the fate of terrigenous dissolved organic nitrogen (DON) in the Arctic Ocean, principal component analyses (PCA) was used on a data set of 13 amino acids released via hydrolyses from a total of 110 water samples from Russian rivers, adjacent near-shore locations and the Laptev Sea. The first component of the PCA distinguished significantly between terrigenous DON from the rivers (1.2 +/-0.1) and marine-derived DON in the deep central Arctic Ocean (-1.1 +/-0.2). The significance of this distinction was validated with amino acid data from seawater and river samples from other regions. The second PCA component correlated significantly with the proportion of D-alanine, a tracer for microbial degradation. The percentage of terrigenous DON in the Arctic Ocean was assessed from the first PCA component. The model was calibrated using the rivers (100% terrigenous) and the deep central Arctic Ocean (approximately 0% terrigenous) as endmembers. Terrigenous DON accounted for 28 +/-13% of the total DON on the Laptev Sea shelf, which is in good agreement with independent, lignin-based estimates. High proportions of terrigenous DON (up to 100%) were calculated for the continental slope down to 2000 m water depth and are probably due to downward convection of brine-enriched shelf waters. The model presented here provides the first direct evidence of terrigenous DON in the deep-sea. It may be directly applied to trace the fate of terrigenous DON in other terrestrially dominated marine environments.

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