@article {Raven2016,
	title = {{Sedimentary pyrite $δ$34S differs from porewater sulfide in Santa Barbara Basin: Proposed role of organic sulfur}},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {186},
	year = {2016},
	pages = {120{\textendash}134},
	abstract = {Santa Barbara Basin sediments host a complex network of abiotic and metabolic chemical reactions that knit together the carbon, sulfur, and iron cycles. From a 2.1-m sediment core collected in the center of the basin, we present high-resolution profiles of the concentrations and isotopic compositions of all the major species in this system: sulfate, sulfide (∑H2S), elemental sulfur (S0), pyrite, extractable organic sulfur (OS), proto-kerogen S, total organic and dissolved inorganic carbon, and total and reducible iron. Below 10 cm depth, the core is characterized by low apparent sulfate reduction rates ({\textless}0.01 mM/yr) except near the sulfate-methane transition zone. Surprisingly, pyrite forming in shallow sediments is \~{}30{\textperthousand} more 34S-depleted than coexisting ∑H2S in porewater. S0 has the same strongly 34S-depleted composition as pyrite where it forms near the sediment{\textendash}water interface, though not at depth. This pattern is not easily explained by conventional hypotheses in which sedimentary pyrite derives from abiotic reactions with porewater ∑H2S or from the products of S0 disproportionation. Instead, we propose that pyrite formation in this environment occurs within sulfate reducing microbial aggregates or biofilms, where it reflects the isotopic composition of the immediate products of bacterial sulfate reduction. Porewater ∑H2S in Santa Barbara Basin may be more 34S-enriched than pyrite due to equilibration with relatively 34S-enriched OS. The difference between OS and pyrite $δ$34S values would then reflect the balance between microbial sulfide formation and the abundance of exchangeable OS. Both OS and pyrite $δ$34S records thus have the potential to provide valuable information about biogeochemical cycles and redox structure in sedimentary paleoenvironments.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	doi = {10.1016/j.gca.2016.04.037},
	author = {Raven, M R and Sessions, A L and Fischer, W W and Adkins, J F}
}
@article {Bennett2011a,
	title = {{Tracing iron-fueled microbial carbon production within the hydrothermal plume at the Loihi Seamount}},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {75},
	number = {19},
	year = {2011},
	pages = {5526{\textendash}5539},
	abstract = {The Loihi hydrothermal plume provides an opportunity to investigate iron (Fe) oxidation and microbial processes in a system that is truly Fe dominated and distinct from mid-ocean ridge spreading centers. The lack of hydrogen sulfide within the Loihi hydrothermal fluids and the presence of an oxygen minimum zone at this submarine volcano{\textquoteright}s summit, results in a prolonged presence of reduced Fe within the dispersing non-buoyant plume. In this study, we have investigated the potential for microbial carbon fixation within the Loihi plume. We sampled for both particulate and dissolved organic carbon in hydrothermal fluids, microbial mats growing around vents, and the dispersing plume, and carried out stable carbon isotope analysis on the particulate fraction. The $δ$13C values of the microbial mats ranged from -23{\textperthousand} to -28{\textperthousand}, and are distinct from those of deep-ocean particulate organic carbon (POC). The mats and hydrothermal fluids were also elevated in dissolved organic carbon (DOC) compared to background seawater. Within the hydrothermal plume, DOC and POC concentrations were elevated and the isotopic composition of POC within the plume suggests mixing between background seawater POC and a 13C-depleted hydrothermal component. The combination of both DOC and POC increasing in the dispersing plume that cannot solely be the result of entrainment and DOC adsorption, provides strong evidence for in-situ microbial productivity by chemolithoautotrophs, including a likelihood for iron-oxidizing microorganisms.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2011.06.039},
	url = {http://dx.doi.org/10.1016/j.gca.2011.06.039},
	author = {Bennett, S A and Hansman, R L and Sessions, A L and Nakamura, K and Edwards, K J}
}
