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Two Chemically Distinct Pools of Organic Nitrogen

Summary: Two Chemically Distinct
Pools of Organic Nitrogen
Accumulate in the Ocean
Lihini I. Aluwihare,1
* Daniel J. Repeta,2
Silvio Pantoja,3
Carl G. Johnson2
The chemical dynamics of marine dissolved organic nitrogen (DON), a reser-
voir featuring surface accumulations even in areas where nitrogen limits pro-
ductivity, have yet to be resolved. We exploited differences in the acid lability
of amide bonds within high-molecular-weight (HMW) DON to show that ver-
tical 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 there-
fore, most HMWDON, is present in amides that resist both chemical hydrolysis
and biological degradation.
Low concentrations of inorganic nitrogen (such
as nitrates and ammonia) are assumed to lim-
it primary production over wide expanses of
the surface ocean. However, in many of these


Source: Aluwihare, Lihini - Geosciences Research Division, Scripps Institution of Oceanography


Collections: Geosciences