HR: 0830h
AN: OS41A-10    [Abstracts]
TI: Seasonal Variation of Sea Surface Chlorophyll a in the Gulf of Mexico
AU: * Yuan, J
EM: jinchun.yuan@usm.edu
AF: The University of Southern Mississippi, 1020 Balch Blvd, Stennis Space Center, MS 39529
AU: Dagg, M
EM: mdagg@lumcon.edu
AF: Louisiana Universities Marine Consortium, 8124 Highway 56, Chauvin, LA 70344
AU: Namwamba, F
EM: fulbertnamwamba@engr.subr.edu
AF: Southern University and A&M College, The Center for Energy and Environmental Studies, Baton Rouge, LA 70813
AU: Lyles, L
EM: LionelLyles@aol.com
AF: Southern University and A&M College, The Center for Energy and Environmental Studies, Baton Rouge, LA 70813
AB: The concentration of chl a is related to phytoplankton biomass and is therefore an important parameter characterizing the trophic state of marine ecosystems. The distribution of chl a in surface waters has been monitored on a daily basis by the space-borne SeaWiFS instrument for more than six years. Early algorithms for calculating chl a were susceptible to interference in Case II waters, but recent studies indicate that the new OC4 algorithm performs well in coastal seawaters. We processed six years of daily SeaWiFS images for surface water chl a of the Gulf of Mexico using the OC4 algorithm. Additionally, we conducted an analysis of temporal and spatial variations of surface water chl a based on its daily distributions. Our analysis indicates that the concentrations of chl a were high in coastal and low in offshore waters consistent with the nutrient limitation of its growth and nutrient sources from rivers and continental shelf. Three belts of high chl a regions were observed including: Texas to Alabama shelf, west Florida shelf, and Campeche/Yucatan shelf. These belts coincide with the wide continental shelf and its shallow water, indicating the contribution to surface biomass by benthic and recycled nutrients. Fluvial nutrients are likely a significant source for Texas to Alabama shelf where highest chl a concentrations were observed. Strong seasonal cycles of chl a concentration were observed throughout the Gulf of Mexico. Two phytoplankton blooms were observed near the northern and southern coasts. The blooms near the northern coast were in March and June likely related to the peak of fluvial nutrient input and solar radiation maximum. The blooms near the southern coast were in July to August and in October and coincide with the seasonal maximum of benthic fluxes. Only one phytoplankton bloom was observed in the offshore waters of the Gulf of Mexico likely fueled by winter mixing and its nutrient input.
DE: 4845 Nutrients and nutrient cycling
DE: 4847 Optics
DE: 4855 Plankton
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly