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Carbon dynamics and community production in the Mississippi River plume
Author(s) -
Guo Xianghui,
Cai Wei-Jun,
Huang Wei-Jen,
Wang Yongchen,
Chen Feizhou,
Murrell Michael C.,
Lohrenz Steven E.,
Jiang Li-Qing,
Dai Minhan,
Hartmann Justin,
Lin Qi,
Culp Randy
Publication year - 2012
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2012.57.1.0001
Subject(s) - plume , alkalinity , dissolved organic carbon , environmental science , oceanography , salinity , total inorganic carbon , seawater , nutrient , phytoplankton , carbonate , hypoxia (environmental) , hydrology (agriculture) , panache , saturation (graph theory) , carbon dioxide , geology , chemistry , oxygen , geography , geotechnical engineering , organic chemistry , meteorology , mathematics , combinatorics
Dissolved inorganic carbon (DIC), total alkalinity (TAlk), pH, and dissolved oxygen (DO) were determined in the Mississippi River plume during five cruises conducted in the spring, summer, and fall. In contrast to many other large rivers, both DIC and TAlk were higher in river water than in seawater. Substantial losses of DIC, relative to TAlk, occurred within the plume, particularly at intermediate salinities. DIC removal was accompanied by high DO, high pH, and nutrient depletion, and was attributed to high phytoplankton production. As a result, the carbonate saturation in the plume became much higher than in ocean and river waters. A mixing model was used to determine DIC removal. We provide evidence that the use of a two—end‐member (river and ocean) mixing model was valid during late summer and fall (low discharge period). However, for other periods we used salinity and TAlk to delineate a mixing model that included two river end members and an ocean end member. Net community production rates in the plume, estimated using a box model, peaked in the summer and were among the highest reported to date for large river plumes. In the summer and fall, biological production in the river plume consumed a majority of the available nutrients, whereas during the spring only a small fraction of the available nutrients were consumed in the plume. Biological production was the dominant process influencing pH and carbonate saturation state along the river—ocean gradient, whereas physicochemical dynamics of mixing played an important role in controlling the TAlk and DIC distributions of this large river plume.