Abstract
Surface ocean marine dissolved organic matter (DOM) serves as an
important reservoir of carbon (C), nitrogen (N), and phosphorus (P) in
the global ocean, and is produced and consumed by both autotrophic and
heterotrophic communities. While prior work has described distributions
of dissolved organic carbon (DOC) and nitrogen (DON) concentrations, our
understanding of DOC:DON:DOP stoichiometry in the global surface ocean
has been limited by the availability of DOP concentration measurements.
Here we estimate mean surface ocean bulk and labile DOC:DON:DOP
stoichiometry in biogeochemically and geographically defined regions,
using newly available marine DOM concentration databases. Global mean
surface ocean bulk (C:N:P = 387:26:1) and labile (C:N:P = 179:20:1) DOM
stoichiometries are higher than Redfield stoichiometry, with labile DOM
stoichiometry similar to that of global mean surface ocean particulate
organic matter (C:N:P = 160:21:1) reported in a recent compilation. DOM
stoichiometry varies across ocean basins, ranging from 251:17:1 to
638:43:1 for bulk and 83:15:1 to 414:49:1 for labile DOM C:N:P,
respectively. Surface ocean DOP exhibits larger relative changes than
DOC and DON, driving surface ocean gradients in DOC:DON:DOP
stoichiometry. Inferred autotrophic consumption of DOP helps explain
intra- and inter-basin patterns of marine DOM C:N:P stoichiometry, with
regional patterns of water column denitrification and iron supply
influencing the biogeochemical conditions favoring DOP use as an organic
nutrient. Specifically, surface ocean marine DOM exhibits increasingly
P-depleted stoichiometries from east to west in the Pacific and from
south to north in the Atlantic consistent with patterns of increasing P
stress and alleviated iron stress, respectively.