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Updated: Jul 11, 2026

Unraveling the Unseen Players in the Ocean - A Field Guide to Water Chemistry and Marine Microbiology
Published on: November 5, 2014
Two chemically distinct pools of organic nitrogen accumulate in the ocean
Lihini I Aluwihare1, Daniel J Repeta, Silvio Pantoja
1Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093, USA. laluwihare@ucsd.edu
Abstract:
The chemical dynamics of marine dissolved organic nitrogen (DON), a reservoir featuring surface accumulations even in areas where nitrogen limits productivity, have yet to be resolved. We exploited differences in the acid lability of amide bonds within high-molecular-weight (HMW) DON to show that vertical DON profiles result in part from the presence of two chemically distinct pools of amide. Half of HMWDON in surface waters is present as N-acetyl amino polysaccharides. In contrast, nearly all deep-sea HMWDON, and therefore, most HMWDON, is present in amides that resist both chemical hydrolysis and biological degradation.
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