M. Mccarthy et al., MAJOR BIOCHEMICAL-COMPOSITION OF DISSOLVED HIGH-MOLECULAR-WEIGHT ORGANIC-MATTER IN SEAWATER, Marine chemistry, 55(3-4), 1996, pp. 281-297
Ultrafiltered dissolved organic matter (UDOM) was isolated from surfac
e, oxygen minimum, and deep waters of three ocean basins and its eleme
ntal as well as molecular-level aldose and amino acid compositions wer
e determined. Surface concentrations account for 23-33% of total disso
lved organic carbon, and are a factor of 2-3 greater than those in dee
per waters. Oceanic UDOM has an extremely characteristic organic compo
sition, clearly distinct from other marine materials such as fresh pla
nkton, sinking particles or humic substances. Polysaccharides appear t
o be the major reactive component of UDOM. They have a distinctive ald
ose distribution rich in galactose and deoxy sugar that is almost ubiq
uitous regardless of depth or location, suggesting that UDOM carbohydr
ate is dominated by a very similar suite of polysaccharide throughout
the ocean. In contrast, amino acids account for a relatively minor com
ponent of both total UDOM and of its organic nitrogen component. Amino
acid distributions are similar to those from unfractionated seawater,
and are not preferentially remineralized.Tn O-2 minimum and deep ocea
n water, ultrafiltered material accounts for 18-25% of total dissolved
organic carbon. Compositions are nearly invariant in these subsurface
isolates, suggesting that ultrafiltered material is stable and unreac
tive throughout the subsurface ocean. Taken together with large compos
itional differences between UDOM and sinking particles, this observati
on suggests that dynamic aggregation is probably not an important form
ation or removal process for UDOM in the deep ocean. Amino acid and es
pecially carbohydrate concentrations are lower in deep UDOM, but the o
verall molecular-level compositions remain similar to those from surfa
ce waters. This molecular-level homogeneity suggests that the UDOM bio
polymers reflected in amino acid and carbohydrate data persist relativ
ely unaltered in the deep ocean.