HR: 15:25h
AN: OS43C-08    [Abstracts]
TI: Importance of Bottom Nephelolid Layers on the Transport and Delivery of Ssediment to the Eastern Cariaco Basin, Venezuela
AU: * Lorenzoni, L
EM: laural@marine.usf.edu
AF: University of South Florida, College of Marine Science, St. Petersburg, FL 33701, United States
AU: Muller-Karger, F E
EM: carib@marine.usf.edu
AF: University of South Florida, College of Marine Science, St. Petersburg, FL 33701, United States
AU: Thunell, R C
EM: thunell@geol.sc.edu
AF: University of South Carolina, Department of Geological Sciences, Coumbia, SC 29208, United States
AU: Tappa, E
EM: ejt@geol.sc.edu
AF: University of South Carolina, Department of Geological Sciences, Coumbia, SC 29208, United States
AU: Benitez-Nelson, C
EM: cbnelson@geol.sc.edu
AF: University of South Carolina, Department of Geological Sciences, Coumbia, SC 29208, United States
AU: Hollander, D
EM: davidh@marine.usf.edu
AF: University of South Florida, College of Marine Science, St. Petersburg, FL 33701, United States
AU: Varela, R
EM: rvarela@edimar.org
AF: Fundación La Salle de Ciencias Naturales, EDIMAR, Apartado Postal 144, Porlamar, 6310, Venezuela
AU: Astor, Y
EM: yastor@edimar.org
AF: Fundación La Salle de Ciencias Naturales, EDIMAR, Apartado Postal 144, Porlamar, 6310, Venezuela
AU: Hu, C
EM: hu@marine.usf.edu
AF: University of South Florida, College of Marine Science, St. Petersburg, FL 33701, United States
AB: Due to their high topographic relief and susceptibility to erosion, mountainous coastal rivers may potentially deliver high sediment and organic matter loads to continental margins. Three small mountainous rivers (Manzanares, Neveri and Unare) that empty onto the shelf of the eastern Cariaco Basin (Venezuela) were examined during the rainy season in September 2003 and 2006 under the framework of the CARIACO (CArbon Retention In A Colored Ocean) Time-Series Project. Optical transmissometer measurements were coupled with particulate organic matter (POM) samples collected in the water column and near the bottom. Suspended sediments entering the basin sink rapidly to the bottom close to the mouth of the rivers (< 10 km). Over the shelf, river sediments dispersed via bottom nepheloid layers (BNL) up to 50 km from the source, reaching the 100m isobath. BNL were observed near the mouths of the three rivers, varying in thickness from 2 to 20 m, with the thickest and most extended BNL observed off the Unare River. BNL particle concentrations were 2-60% higher than water column values. Most of the BNL were lower in particulate organic carbon (POC), nitrogen (PON) and phosphate (POP) (~85 mg C m^-3, ~9.6 mg N m^-3, ~ 0.8 mg P m^-3, respectively), compared to measurements in the overlying water column (~100 mg C m^-3, ~10.7 mg N m^-3, ~ 0.92 mg P m^-3, respectively), suggesting that BNL are not a primary mechanism for delivering terrigenous POM to the deeper anoxic waters of the Cariaco Basin during the rainy season. Nonetheless, terrigenous sediments originating in the Cordillera de la Costa (Coastal Mountain Range) of Venezuela are found in the deep sediments of Cariaco Basin, and thus may serve as important components of mineral ballast that acts to transport POC from surface waters to depth. BNL also represent a potential, transitory source of iron to the suboxic zone of the Cariaco Basin.
DE: 3022 Marine sediments: processes and transport
DE: 4211 Benthic boundary layers
DE: 4219 Continental shelf and slope processes (3002)
DE: 4273 Physical and biogeochemical interactions
DE: 4558 Sediment transport (1862)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting