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La Salle, Venezuela

Lorenzoni L.,University of South Florida | Taylor G.T.,State University of New York at Stony Brook | Benitez-Nelson C.,University of South Carolina | Hansell D.A.,University of Miami | And 7 more authors.
Journal of Geophysical Research: Biogeosciences | Year: 2013

Dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) were measured monthly at the CARIACO Time Series station (10°30′N, 64°40′W) in the southeastern Caribbean Sea between 2005 and 2012. Marked seasonal variability in DOC concentrations was observed, with lower values (∼66 μM) in the upper water column (<75 m) during the upwelling season (December-April) due to the injection of cool, DOC-impoverished Subtropical Underwater from the Caribbean Sea. During the rainy season (May-November) waters were stratified and upper layer DOC concentrations increased to ∼71 μM. Interannual variability in surface (1 m) concentrations of DOC was also observed in response to the variable strength in upwelling and stratification that the Cariaco Basin experienced. DON and DOP showed no such seasonality. At depths >350 m, DOC concentrations were 56 ± 4.7 μM, roughly 10 μM higher than those in the Caribbean Sea over the same depth range. DON and DOP showed similar vertical profiles to that of DOC, with higher concentrations (6.8 ± 1.2 μM N and 0.15 ±0.09 μM P) in the upper water column and invariant, lower concentrations at depth (4.8 ± 1.6 μM N and 0.10 ± 0.08 μM P). Wind-driven advection of surface DOC out of the Cariaco Basin was estimated to support a net export ∼15 Gmol C yr-1 into the Caribbean Sea; this rate is comparable to the flux of settling particulate organic carbon to depths >275 m within the basin. Key Points We present a 7 year time-series on DOM in the Cariaco BasinWe highlight the importance of microbially-mediated DOM in anoxic watersThe horizontal export of DOC from the Basin varies interannually ©2013. American Geophysical Union. All Rights Reserved. Source


Bozo-Hurtado L.,Simon Bolivar University of Venezuela | Garcia-Amado M.A.,Venezuelan Institute for Scientific Research | Chistoserdov A.,University of Louisiana at Lafayette | Varela R.,EDIMAR | And 3 more authors.
Aquatic Biosystems | Year: 2013

Background: The Cariaco Basin is characterized by pronounced and predictable vertical layering of microbial communities dominated by reduced sulfur species at and below the redox transition zone. Marine water samples were collected in May, 2005 and 2006, at the sampling stations A (10°30′ N, 64°40′ W), B (10°40′ N, 64°45′ W) and D (10°43'N, 64°32'W) from different depths, including surface, redox interface, and anoxic zones. In order to enrich for sulfate reducing bacteria (SRB), water samples were inoculated into anaerobic media amended with lactate or acetate as carbon source. To analyze the composition of enrichment cultures, we performed DNA extraction, PCR-DGGE, and sequencing of selected bands.Results: DGGE results indicate that many bacterial genera were present that are associated with the sulfur cycle, including Desulfovibrio spp., as well as heterotrophs belonging to Vibrio, Enterobacter, Shewanella, Fusobacterium, Marinifilum, Mariniliabilia, and Spirochaeta. These bacterial populations are related to sulfur coupling and carbon cycles in an environment of variable redox conditions and oxygen availability.Conclusions: In our studies, we found an association of SRB-like Desulfovibrio with Vibrio species and other genera that have a previously defined relevant role in sulfur transformation and coupling of carbon and sulfur cycles in an environment where there are variable redox conditions and oxygen availability. This study provides new information about microbial species that were culturable on media for SRB at anaerobic conditions at several locations and water depths in the Cariaco Basin. © 2013 Bozo-Hurtado et al.; licensee BioMed Central Ltd. Source


Garcia-Amado M.A.,Venezuelan Institute for Scientific Research | Bozo-Hurtado L.,Simon Bolivar University of Venezuela | Astor Y.,EDIMAR | Suarez P.,Simon Bolivar University of Venezuela | Chistoserdov A.,University of Louisiana at Lafayette
FEMS Microbiology Ecology | Year: 2011

The Cariaco system is the second largest permanently anoxic marine water body in the world. Its water column is characterized by a pronounced vertical layering of microbial communities. The goal of our study was to investigate the vertical distribution and diversity of Vibrio spp. present in the Cariaco Basin waters using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA fragments. Representatives of the Vibrio genus were detected by nested and direct PCR in seawater at 10 depths. Sequence analyses of 55 DGGE bands revealed that only 11 different operational taxonomic units (OTU) are identified as Vibrio species. Between one and five OTUs were detected at each depth and the most common OTUs were OTU 1 and OTU 2, which phylogenetically clustered with Vibrio chagasii and Vibrio fortis, respectively. OTUs 3 and 4 were only found in the anoxic zone and were identified as Vibrio orientalis and Vibrio neptunius, respectively. Several Vibrio species detected are potentially pathogenic to human, prawns and corals such as Vibrio parahaemolyticus, Vibrio fischeri and Vibrio shilonii. In the Cariaco Basin, different Vibrio species were found to be specific to specific depths strata, suggesting that this genus is a natural component of the microbial communities in this marine redox environment. © 2011 Federation of European Microbiological Societies. Source

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