Carbon Dynamics and Community Production in the Mississippi River Plume

Authors

Xianghui Guo, University of GeorgiaFollow
Wei-Jun Cai, University of GeorgiaFollow
Wei-Jen Huang, University of GeorgiaFollow
Yongchen Wang, University of GeorgiaFollow
Feizhou Chen, University of Georgia
Michael C. Murrell, U.S. Environmental Protection AgencyFollow
Steven E. Lohrenz, University of Southern MississippiFollow
Li-Qing Jiang, University of GeorgiaFollow
Minhan Dai, Xiamen UniversityFollow
Justin Hartmann, University of Georgia
Qi Lin, Third Institute of Oceanography
Randy Culp, University of GeorgiaFollow

Document Type

Article

Publication Date

1-1-2012

Department

Marine Science

School

Ocean Science and Engineering

Abstract

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.

Publication Title

Limnology and Oceanography

Volume

57

Issue

1

First Page

1

Last Page

17

Recommended Citation

Guo, X., Cai, W., Huang, W., Wang, Y., Chen, F., Murrell, M. C., Lohrenz, S. E., Jiang, L., Dai, M., Hartmann, J., Lin, Q., Culp, R. (2012). Carbon Dynamics and Community Production in the Mississippi River Plume. Limnology and Oceanography, 57(1), 1-17.
Available at: https://aquila.usm.edu/fac_pubs/122