Effect of summertime shelf break upwelling on nutrient flux in southeastern United States continental shelf waters
Gulf Stream-induced upwellng at the shelf break of the South Atlantic Bight (SAB) presents water which, in summer, can intrude onto the continental shelf. In July 1979, an XBT survey of the continental shelf revealed such an intrusion of cold water off St. Augustine, Florida. From weekly mappings, it was determined that Gulf Stream water < 22.5/sup 0/C covered 3280 km/sup 2/ and occupied 38 km/sup 3/ shoreward of the 42 m isobath. Using temperature and nitrate distributions and the T/sup 0/C:NO/sup 3/ relationship, the authors determined that 3200 metric tons of nitrate-nitrogen were advected into the study area. Net nitrate-nitrogen fluxes were 32 ..mu..moles x m/sup -2/ x sec /sup -1/ across the 42 m isobath and 30 ..mu..moles x m/sup -2/ x sec /sup -1/ across the 30 m isobath. The advection of nitrate-enriched water into the photic zone caused a dramatic increase in phytoplankton biomass. The decreasing nitrate concentrations correlated with chlorophyll increases indicating phytoplankton production was mainly at the expense of nitrate advected into the area. Prior to the intrusion, production was likely supported by regenerated nutrients. Summertime intrusions supply an estimated 2.9 x 10/sup 4/ mtons NO/sub 3/-N x yr/sup -1/ to the middle shelf area of the southern SAB and are thus a major source of nitrogen to that area. 32 references, 15 figures, 4 tables.
- Research Organization:
- Skidaway Institute of Oceanography, Savannah, GA
- DOE Contract Number:
- AS09-76EV00889; AS09-76EV00936
- OSTI ID:
- 5430636
- Journal Information:
- J. Mar. Res.; (United States), Vol. 42:4
- Country of Publication:
- United States
- Language:
- English
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Effect of summertime shelf break upwelling on nutrient flux in southeastern United States continental shelf waters
Zooplankton abundance in relation to state and type of intrusions onto the southeastern United States shelf during summer
Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
NITROGEN
MINERAL CYCLING
OCEANIC CIRCULATION
SEASONAL VARIATIONS
COASTAL WATERS
CONTINENTAL SHELF
FLORIDA
GULF STREAM
NITRATES
NUTRIENTS
PHYTOPLANKTON
PLANT GROWTH
STIMULATION
USA
AQUATIC ORGANISMS
CONTINENTAL MARGIN
CURRENTS
ELEMENTS
FEDERAL REGION IV
GROWTH
NITROGEN COMPOUNDS
NONMETALS
NORTH AMERICA
OXYGEN COMPOUNDS
PLANKTON
SURFACE WATERS
VARIATIONS
WATER CURRENTS
520100* - Environment
Aquatic- Basic Studies- (-1989)
560303 - Chemicals Metabolism & Toxicology- Plants- (-1987)