Stocks and Dynamics of Dissolved and
Particulate Organic Matter in the Southern
Ross Sea, Antarctica

Craig A. Carlson*¹ and Dennis A. Hansell
Bermuda Biological Station for Research
17 Biological Lane, Ferry Reach
St. Georges, GE-01, BERMUDA.

Edward T. Peltzer
Monterey Bay Aquarium Research Institute
7700 Sandholdt Rd
Moss Landing, CA 95039, USA.

Walker O. Smith Jr.
The College of William and Mary
Virginia Institute of Marine Science
P.O. Box 1346
Gloucester Point, VA 23062, USA.

Deep-Sea Research II (2000) 47: 3201-3225.

Received: 15 June 1999.
Revised: 1 December 1999.
Accepted: 31 January 2000.

* Corresponding author. Fax: 441-297-8143.


¹: Present address: Department of Ecology, Evolution and Marine Biology,
University of California, Santa Barbara, CA 93106-9610, USA.

ABSTRACT

Dissolved and particulate organic matter was measured during six cruises to the southern Ross Sea. The cruises were conducted during late austral winter to autumn from 1994 to 1997 and included coverage of various stages of the seasonal phytoplankton bloom. The data from the various years are compiled into a representative seasonal cycle in order to assess general patterns of dissolved organic matter (DOM) and particulate organic matter (POM) dynamics in the southern Ross Sea. Dissolved organic carbon (DOC) and particulate organic carbon (POC) were at background concentrations of approximately 42 and 3 µM C, respectively, during the late winter conditions in October. As the spring phytoplankton bloom progressed, organic matter increased, and by January DOC and POC reached as high as 30 µM C and 107 µM C, respectively, in excess of initial wintertime conditions. Stocks and concentrations of DOC and POC return to near background values by autumn (April). Approximately 90% of the accumulated organic matter was partitioned into POM, with modest net accumulation of DOM stocks despite large net organic matter production and the dominance of Phaeocystis antarctica. Changes in nitrate concentration from wintertime values were used to calculate the equivalent biological drawdown of dissolved inorganic carbon (DIC-equiv). The fraction of DIC-equiv drawdown resulting in net DOC production was relatively constant (ca.11%), despite large temporal and spatial variability in DIC-equiv drawdown. The C:N (molar ratio) of the seasonally produced DOM had a geometric mean of 6.2 and was nitrogen-rich compared to background DOM. The DOM stocks that accumulate in excess of deep refractory background stocks are often referred to as "semi-labile" DOM. The "semi-labile" pool in the Ross Sea turns over on timescales of about 6 months. As a result of the modest net DOM production and its lability, the role DOM plays in export to the Deep-Sea is small in this region.

© 2000 Elsevier Science Ltd. All rights reserved.


Acknowledgements

We gratefully acknowledge the dedicated support extended by Captain Borkowski and the officers and crew of RVIB Nathaniel B. Palmer and by Antarctic Support Associates. We thank the Chief Scientists Walker Smith, Daria Garrison, John Marra and Hugh Ducklow for cruise planning and leadership. We are grateful to R. Parsons, A. Ritchie, T. Tredennick, F. Howse, A.M. White, S. Polk, J. Seward, and T. Kirchlechner for providing expert field assistance. We thank P. Hansell, C. Adams and G. Leplace for analyses of organic nitrogen reported in this paper and M.P. Otero for assistance with graphics. Thanks to the hydrographic team led by L. Gordon and L. Codispoti. We are grateful to P.J. leB Williams, A. Skoog, R. Anderson and P. Kahler for their helpful comments. This work was supported by NSF grants OPP 93-17200 to D.A.H., OCE 95-30845 to D.A.H. and C.A.C., OPP 95-30609 to E.T.P. and OPP 95-31990 to W.O.S. This is BBSR contribution 1551, VIMS contribution 2292, and US JGOFS contribution 547.


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