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Influence of bacterial uptake on deep‐ocean dissolved organic carbon
Author(s) -
Bendtsen Jørgen,
Lundsgaard Claus,
Middelboe Mathias,
Archer David
Publication year - 2002
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2002gb001947
Subject(s) - photic zone , deep sea , dissolved organic carbon , environmental science , oceanography , microbial loop , deep ocean water , biological pump , carbon fibers , carbon cycle , environmental chemistry , atmosphere (unit) , flux (metallurgy) , seawater , particulates , total organic carbon , organic matter , particulate organic carbon , heterotroph , chemistry , phytoplankton , geology , nutrient , ecology , bacteria , ecosystem , biology , meteorology , materials science , composite number , composite material , paleontology , physics , organic chemistry
Particulate organic carbon (POC) sinking out of the sunlit euphotic zone at the surface of the ocean feeds the deep sea and alters the CO 2 concentration of the atmosphere. Most of the sinking POC is reoxidized to dissolved inorganic carbon (DIC) before it hits the sea floor, but the mechanism for this is poorly understood. Here we develop a global model of the microbial loop in the aphotic zone based on new measurements of deep ocean bacterial metabolism. These together imply that a significant fraction of the decreasing POC flux with depth is converted to dissolved organic carbon (DOC) rather than directly to DIC as is commonly assumed, thereby providing the substrate for free‐living bacteria in the deep ocean. The model suggests the existence of a substantial DOC‐pool with a relatively fast turnover time in the deep sea. By implementing the microbial loop in a model of the global ocean circulation, we show that the observed gradient of DOC in the deep North Atlantic can be explained by the temperature dependence of bacterial metabolic activity in conjunction with the formation of deep‐water at high latitudes.