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Papers by Mary I. Scranton

AGU Fall Meeting Abstracts, Dec 1, 2008

Earth-Science Reviews, Sep 1, 1987

Analytical Chemistry, Mar 1, 1993

ABSTRACT

Limnology and Oceanography Bulletin, May 1, 2012

In the Cariaco Basin, off the coast of Venezuela, a well-developed 150-m thick series of chemocli... more In the Cariaco Basin, off the coast of Venezuela, a well-developed 150-m thick series of chemoclines lie between oxygenated surface waters and sulfidic bottom waters. Various reductants (H2S, NH4+, CH4, Fe2+, Mn2+) and oxidants (O2, MnO2, Fe2O3, NO3- S2O32-, SO32-, S0) are present as potential substrates for chemoautotrophy. Microbial processes within the chemoclines support a diverse microbial community that produces diagnostic lipid biomarkers. Lipid biomarker analysis within the chemocline of the Cariaco Basin shows that the chemocline is itself a multilayer biogeochemical system. Using large volume in situ filtration, we collected a high resolution a set of suspended particulate matter (SPM) samples within the chemocline for analyses of intact lipids indicative of microbial processes, with concurrent measurements for microbiology and chemistry. These comprehensive, multidimensional data allows us to define linkages between lipid biomarkers, distributions of major chemical species, and microbial community structure within the chemocline. Our results allow us to partition the chemocline into (at least) three subregions, with a thin (15-20 m) core zone being a ``hotspot'' of microbial activity, chemoautotrophic production of new organic matter (OM) and biomarkers diagnostic of microbial production. The core chemocline zone is especially rich in a new suite of biomarkers, methoxy fatty acids. Stable isotope probing experiments show that the methoxy fatty acids, as well as other lipids, are derived from chemoautotrophic, sulfur oxidizing bacteria.

AGU Fall Meeting Abstracts, Dec 16, 2015

AGU Fall Meeting Abstracts, Dec 1, 2008

ABSTRACT The detailed distribution of sulfur isotopes was studied in the water column of the Cari... more ABSTRACT The detailed distribution of sulfur isotopes was studied in the water column of the Cariaco Basin, with high depth resolution across the redox transition zone, in Nov. 2007 and May 2008 as part of the on-going CARIACO (CArbon Retention In A Colored Ocean) time series project. Long term monitoring (1995 to present) of the vertical position of the chemocline (200-350 m) and thickness of the suboxic zone (0-50 m) reveals highly dynamic spatial and temporal variability tied to the influx of oxygenated water into the restricted basin. The link between the basin hydrography and chemoautotrophic activity is potentially expressed in chemical speciation and composition of sulfur compounds cycled within the chemocline. For Nov. 2007 cruise, we measured the delta34S of total dissolved sulfide (delta34SH2S) and sulfate (delta34SSO4), and the delta18O of sulfate (delta18OSO4) from water samples. In close agreement with results from the Black Sea, delta34SH2S, delta34SSO4 and delta18OSO4 were relatively constant in the deep anoxic water, with the delta34SH2S depleted in 34S relative to delta34SSO4 by roughly 50 permil. However, near the oxic-anoxic interface, delta34SH2S was 3 permil higher than that in the deep water due to sulfide oxidation and/or in situ sulfide production. In May 2008, we collected water samples to measure three sulfur isotopes (33S, 34S and 36S) in sulfate, sulfide and elemental sulfur to explore the contribution of biological processes (sulfate reduction, sulfur intermediates disproportionation, and chemoautotrophic sulfur oxidation) to the isotopic composition of sulfur compounds in the basin. Also during the same cruise, an oxygen intrusion event was observed and we will present sulfur isotope data associated with that event.