Marine Biology

, Volume 87, Issue 1, pp 19–32 | Cite as

Shallow-water benthic and pelagic metabolism:

evidence of heterotrophy in the nearshore Georgia Bight
  • C. S. HopkinsonJr.


Pelagic primary production and benthic and pelagic aerobic metabolism were measured monthly at one site in the estuarine plume region of the nearshore continental shelf in the Georgia Bight. Benthic and water-column oxygen uptake were routinely measured and supplemented with seasonal measures of total carbon dioxide flux. Average respiratory quotients were 1.18:1 and 1.02:1 for the benthos and water column, respectively. Benthic oxygen uptake ranged from 1.23 to 3.41 g O2 m-2 d-1 and totalled 756 g O2 m-2 over an annual period. Water column respiration accounted for 60% of total system metabolism. Turnover rates of organic carbon in sediment and the water column were 0.09 to 0.18 yr-1 and 6.2 yr-1, respectively. Resuspension appeared to control the relative amounts of organic carbon, as well as the sites and rates of organic matter degradation in the benthos and water column. Most of the seasonal variation in benthic and pelagic respiration could be explained primarily by temperature and secondarily by primary productivity. On an annual basis, the shelf ecosystem appeared to be heterotrophic; primary production was 73% of community metabolism, which was 749 g C m-2 yr-1. The timing of heterotrophic periods through the year appeared to be closely related to both river discharge and the periodicity of growth and death of marsh macrophytes in the adjacent estuary. The results of this study support the estuarine “outwelling” hypothesis of Odum (1968).


Macrophyte Continental Shelf Organic Matter Degradation Carbon Dioxide Flux Plume Region 
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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • C. S. HopkinsonJr.
    • 1
  1. 1.University of Georgia Marine InstituteSapelo IslandUSA

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