Dissolved organic carbon in the Mid-Atlantic Bight

The Mid-Atlantic Bight (MAB) is a highly productive continental shelf region on the eastern North American coast and a potential sight for the export of organic carbon to the open ocean. The dynamics of dissolved organic carbon (DOC) in the MAB were studied during three cruises in April 1994, March 1996 and August 1996 in order to characterize DOC distributions on the shelf, estimate inventories of DOC on the shelf and quantify DOC transport. There were clear spatial and temporal trends in DOC distributions. Concentrations of DOC were greater inshore than offshore and increased southward along the shelf. The total DOC inventory on the shelf during the March and April cruises was estimated at B5.88 � 10 12 g C and this increased by 0.4 � 10 12 g C (7%) in August. A simple mass balance of DOC input and export in the MAB resulted in total export of 18.7–19.6 � 10 12 gC yr � 1 . Up to 67% of this carbon is recycled oceanic DOC that is refractory with respect to MAB seawater residence times, B4% is introduced through estuaries, sediments and rainwater and at least 29% of the exported shelf DOC (4.1–7.4 � 10 12 gC yr � 1 ) is produced on the shelf. Net ecosystem production of DOC in the MAB is estimated to be between 10% and 18% of MAB primary productivity estimates. Our data supports the hypothesis that the MAB as a whole is net autotrophic for the periods of study and that DOC is an important component in ocean margin carbon budgets. r 2002 Elsevier Science Ltd. All rights reserved.

[1]  Robert F. Chen,et al.  The fluorescence of dissolved organic matter in the Mid-Atlantic Bight , 2002 .

[2]  E. Peltzer,et al.  Some practical aspects of measuring DOC — sampling artifacts and analytical problems with marine samples , 1993 .

[3]  Dennis A. Hansell,et al.  Predominance of vertical loss of carbon from surface waters of the equatorial Pacific Ocean , 1997, Nature.

[4]  P. Falkowski,et al.  Production and transport of phytoplankton biomass over the continental shelf of the new york bight , 1983 .

[5]  Paul G. Falkowski,et al.  The shelf edge exchange processes experiment, SEEP-II: an introduction to hypotheses, results and conclusions , 1994 .

[6]  R. Fairbanks.  The origin of continental shelf and slope water in the New York Bight and Gulf of Maine: Evidence from H2 18O/H2 16O ratio measurements , 1982 .

[7]  J. Bauer,et al.  Ocean margins as a significant source of organic matter to the deep open ocean , 1998, Nature.

[8]  Nicholas R. Bates,et al.  A high resolution study of surface layer hydrographic and biogeochemical properties between Chesapeake Bay and Bermuda , 1999 .

[9]  Robert F. Chen,et al.  Dissolved organic carbon on Georges Bank , 1996 .

[10]  P. Falkowski,et al.  Modeling vertical oxygen and carbon flux during stratified spring and summer conditions on the continental shelf, Middle Atlantic Bight, eastern U.S.A. , 1994 .

[11]  J. Sharp.  The Dissolved Organic Carbon Controversy: An Update , 1993 .

[12]  P. Santschi,et al.  Sedimentary sources of old high molecular weight dissolved organic carbon from the ocean margin benthic nepheloid layer , 2000 .

[13]  J. G. Field,et al.  The Ecological Role of Water-Column Microbes in the Sea* , 1983 .

[14]  E. Druffel,et al.  Radiocarbon in dissolved organic matter in the central North Pacific Ocean , 1987, Nature.

[15]  R. Anderson,et al.  Fluxes of particulate matter on the slope of the southern Middle Atlantic Bight: SEEP-II , 1994 .

[16]  Dennis A. Hansell,et al.  Deep-ocean gradients in the concentration of dissolved organic carbon , 1998, Nature.

[17]  Dennis A. Hansell,et al.  Organic carbon partitioning during spring phytoplankton blooms in the Ross Sea polynya and the Sargasso Sea , 1998 .

[18]  C. Reimers,et al.  Intensification of recycling of organic matter at the sea floor near ocean margins , 1990, Nature.

[19]  C. Culberson,et al.  The chemistry of the Delaware estuary. General considerations1 , 1982 .

[20]  C. McClain,et al.  Role of Gulf Stream frontal eddies in forming phytoplankton patches on the outer southeastern shelf1 , 1981 .

[21]  S. Lohrenz,et al.  Primary production on the continental shelf off Cape Hatteras, North Carolina , 2002 .

[22]  W. Koeve,et al.  Marine dissolved organic matter: can its C : N ratio explain carbon overconsumption? , 2001 .

[23]  M. DeGrandpre,et al.  Seasonal variation of CDOM and DOC in the Middle Atlantic Bight: Terrestrial inputs and photooxidation , 1997 .

[24]  John J. Walsh,et al.  Importance of continental margins in the marine biogeochemical cycling of carbon and nitrogen , 1991, Nature.

[25]  K. Johnson,et al.  Fluxes of dissolved organic carbon from California continental margin sediments , 1999 .

[26]  J. Southon,et al.  Cycling of high-molecular-weight dissolved organic matter in the Middle Atlantic Bight as revealed by carbon isotopic (13C and 14C) signatures , 1996 .

[27]  P. Falkowski,et al.  The fate of a spring phytoplankton bloom: export or oxidation? , 1988 .

[28]  C. Hopkinson,et al.  Stoichiometry of dissolved organic matter dynamics on the continental shelf of , 1997 .

[29]  Pierre E. Biscaye,et al.  Fluxes of particles and constituents to the eastern United States continental slope and rise: SEEP—I , 1988 .

[30]  J. Willey,et al.  Rainwater dissolved organic carbon: Concentrations and global flux , 2000 .

[31]  Dennis A. Hansell,et al.  Chemical characterization of three large oceanic diatoms: potential impact on water column chemistry , 1992 .

[32]  J. Hagy,et al.  Dissolved and particulate organic carbon in Chesapeake Bay , 1998 .

[33]  W. Balzer,et al.  Release of dissolved organic carbon (DOC) from sediments of the N.W. European Continental Margin (Goban Spur) and its significance for benthic carbon cycling , 1998 .

[34]  P. Falkowski,et al.  The lateral flux of biogenic particles from the eastern North American continental margin to the North Atlantic Ocean , 1994 .

[35]  H. Ducklow,et al.  Annual flux of dissolved organic carbon from the euphotic zone in the northwestern Sargasso Sea , 1994, Nature.

[36]  S. Lohrenz,et al.  Phytoplankton dynamics within a discrete water mass off Cape Hatteras, North Carolina: the Lagrangian experiment , 2002 .

[37]  Walker O. Smith,et al.  The US Southern Ocean Joint Global Ocean Flux Study: an introduction to AESOPS , 2000 .

[38]  J. Peixoto,et al.  Physics of climate , 1992 .

[39]  R. Benner,et al.  What happens to terrestrial organic matter in the ocean , 1997 .

[40]  N. Ogura.  Rate and extent of decomposition of dissolved organic matter in surface seawater , 1972 .

[41]  D. Mountain.  The volume of Shelf Water in the Middle Atlantic Bight: seasonal and interannual variability, 1977–1987 , 1991 .

[42]  H. Ducklow,et al.  High turnover rates of dissolved organic carbon during a spring phytoplankton bloom , 1991, Nature.

[43]  D. Wallace.  Anthropogenic chlorofluoromethanes and seasonal mixing rates in the Middle Atlantic Bight , 1994 .

[44]  David L. Evans,et al.  Shelf water entrainment by Gulf Stream warm-core rings , 1987 .

[45]  Dennis A. Hansell,et al.  Net community production of dissolved organic carbon , 1998 .

[46]  E. Peltzer,et al.  A comparison of methods for the measurement of dissolved organic carbon in natural waters , 1996 .

[47]  R. Pocklington,et al.  Seasonal and annual variations in the organic matter contributed by the St Lawrence River to the Gulf of St. Lawrence , 1987 .

[48]  M. DeGrandpre,et al.  Air–sea CO2 fluxes on the US Middle Atlantic Bight , 2002 .

[49]  J. Walsh,et al.  The 1983-1984 Shelf Edge Exchange Processes (SEEP)--I experiment: hypotheses and highlights , 1988 .

[50]  K. J. Richards,et al.  Evolution of physical oceanography , 1982 .

[51]  J. Bauer,et al.  Cycling of dissolved and particulate organic matter in the open ocean , 1992 .

[52]  E. Peltzer,et al.  Spatial and temporal variability of total organic carbon along 140°W in the equatorial Pacific Ocean in 1992 , 1996 .

[53]  F. F. Pérèz,et al.  Net ecosystem production of dissolved organic carbon in a coastal upwelling system: the Ría de Vigo, Iberian margin of the North Atlantic , 2001 .

[54]  P. Wangersky.  Dissolved organic carbon methods: a critical review , 1993 .

[55]  K. Mopper,et al.  Automated High-Performance, High-Temperature Combustion Total Organic Carbon Analyzer , 1996 .