Dissolved Organic Carbon on Georges Bank

Robert F. Chen
University of Massachusetts - Boston
Environmental Sciences Program
100 Morriseey Boulevard
Boston, Massachusetts 02125-3393 USA

Brian Fry¹ and Chuck S. Hopkinson
Marine Ecosystems Group
Marine Biological Laboratory
Woods Hole, Massachusetts 02543 USA

Daniel J. Repeta and Edward T. Peltzer
Woods Hole Oceanographic Institutiton
Woods Hole, Massachusetts 02543 USA

Continental Shelf Research (1996) 16: 409-420.

Received: 17 November 1994.
Accepted: 12 January 1995.
Published: April 1995.


¹: Current address: Biology Dept, Florida International University, University Park, Miami FL 33199.

ABSTRACT

Dissolved organic carbon (DOC) in sea water from Georges Bank was measured by a high temperature combustion / direct injection (HTC/DI) technique during the spring bloom period in April 1993. Concentrations in surface water (72-85 µMC) and deep waters (54-56 µMC) were similar to DOC concentrations measured in the oligotrophic north-west Atlantic Ocean by a number of other investigators by various techniques. Although surface values for Chl-a concentrations ranged from 2 to 5 µg/l, NO3¯ ranged from 3 to 9 µM and particulate organic carbon (POC) concentrations ranged from 1.0 to 10.0 µMC, DOC concentrations only varied by <18%. DOC was slightly higer (~5 µMC) in the highly productive central bank region than in surrounding stratified surface waters. Relatively constant stable carbon isotopes (DO¹³C = -22.0 ± 0.5 o/oo) could not be used to identify a source for these small variations. Slight decreases of DOC (5-12 µMC) and dissolved organic nitrogen (DON) (0.5-1.0 µMN) in filtered sea water kept in the dark was observed over six months, suggesting the presence of a small, labile pool of dissolved organic matter in addition to a large, more refractory reservoir of DOC (~70 µMC) during the spring bloom period on Georges Bank.


Acknowledgements

We thank L. Redmond for filtration, D. Dugan for DOC analyses, A. Nolin for literature DOC summaries, T. I. Eglinton for POC data, J. Irvine for Chl-a data, T. Walsh for nitrate data, and the crews of the R/V Oceanus and R/V Iselin for their support. This work was funded by an NSF Earth Sciences post-doctoral fellowship (EAR-9208842) to R. F. Chen, and DOE Ocean Margins Program grants DE-FG02-92ER61428 to D. J. Repeta and T. I. Eglinton and DE-FG02-92ER61438 to B. Fry and C. S. Hopkinson.


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