Processes of coastal upwelling and carbon flux in the Cariaco Basin

Monthly hydrographic, phytoplankton biomass and primary production, bio-optical observations, and settling particulate organic carbon flux observations were collected at 10.5degreesN, 64.67degreesW within the Cariaco Basin, off Venezuela, for a period exceeding seven years starting in November 1995. These data were combined with a time series of Sea-viewing Wide-Field-of-view Sensor (SeaWiFS), advanced very high-resolution radiometer (AVHRR), and European Remote Sensing Satellite/QuikScat. data to examine the spatial extent of a cold coastal upwelling plume and a phytoplankton bloom associated with it. The seasonal upwelling cycle was directly linked to the intensity of the Trade Winds, with sea-surface temperature (SST) changes lagging the wind by 1-2 weeks. The seasonal cycle of most properties was punctuated by transient phenomena, some of which caused subsurface ventilation and also high primary production events. Integrated primary production ranged from 650, 574, and 593 g C m(-2) yr(-1) in 1996, 1997, and 2001, respectively, to 372, 484, and 448 g C m(-2) yr(-1), respectively, in 1998, 1999, and 2000. The Rutgers vertical generalized production model (VGPM) was modified to reflect an increase in Assimilation Number (PBopt) with SST at the Cariaco time series station, because the original VGPM formulation suggested inhibition of primary production at SST > 21degreesC. Trap observations showed that between 9 and 10 g C m(-2) yr(-1) were delivered to the bottom at the Cariaco time series station, i.e. similar to1.33% of surface primary productivity. Annual particulate organic carbon flux to the bottom over the area of the Cariaco Basin (waters > 100 m), estimated using SeaWiFS and AVHRR variable inputs and the updated VGPM, ranged from 6.77 x 10(10) to 7.61 x 10(10) g C. These are likely underestimates due to lack of bathymetric corrections to flux. (C) 2004 Elsevier Ltd. All rights reserved.