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ABSTRACT Six marine bacterial isolates were obtained from fluid and sediments collected at alkaline serpentinite mud volcanoes of the Mariana forearc to examine life at high pH in a marine environment. Here, we present the draft genome sequences of these six isolates, classified as strains of the speciesMarinobacter shengliensis. 

Dissolved organic carbon (DOC) constitutes the largest pool of reduced carbon in the global ocean, with important contributions from both recently formed and aged, biologically refractory DOC (RDOC). The mechanisms regulating RDOC transformation and removal remain uncertain though hydrothermal vents have been identified as sources and sinks. This study examines RDOC sinks in the deep Pacific Ocean, highlighting the role of submarine hydrothermal systems. Geochemical survey data from GO‐SHIP and GEOTRACES projects, alongside specific investigations of Pacific hydrothermal systems, suggest that particulate iron introduced by hydrothermal systems plays a key role in scavenging DOC and delivering it to the seafloor, leaving a deficit in the RDOC of the deep ocean. Dilution of the oceanic water column by hydrothermal fluids exhibiting low DOC concentrations likely plays a secondary role. 

Treatise of Geochemistry chapter 

Sample description and geochemistry collected from Mariana forearc boreholes with the HOG sampler Project Name: Collaborative Research: Collaborative Research: Characterization of Subduction Channel Processes, Borehole Sampling at Active Serpentinite Mud Volcanoes on the Mariana Funding: NSF-OCE-1921654 Susan Lang, Woods Hole Oceanographic InstitutionForearc NSF-OCE-1922671 Geoff Wheat, University of Alaska Fairbanks NSF-OCE-1921361 Jeff Seewald, Woods Hole Oceanographic Institution   Permits: Mariana Trench National Wildlife Refuge, U.S. Fish & Wildlife Service, Department of the Interior Permit Number: 12541-22009   Project goals: The overarching goal of the project was to understand the reaction processes that occur at depth during subduction. Boreholes drilled during the recent International Ocean Discovery Program Expedition 366 were targeted to collect pristine fluids.    The specific goals of the project were to (1) determine the water-rock reactions that control the chemical composition of deep-sourced fluids ascending from atop a subducting slap (2) identify the processes that regulate the nonbiological formation of methane, and assess its potential metabolic impact (3) characterize the origin and abundance of organic carbon molecules to constrain redox and pH conditions within the subduction channel and shallow subsurface environment and (4) relate the permeability of fluid pathways to seamount structure   Samples were collected during a 25 day expedition with a deep-sea submersible. A CORK-Lite was be deployed at three newly cased boreholes: U1492D (Yinazao), U1497D (Fantangisña), and U1496C (Asùt Tesoru). Fluids discharging from these three new boreholes, and a fourth already cased borehole (U1200C, South Chamorro), were collected for inorganic and organic geochemical analysis. Dataset Description: Table 1. Sample Logs. Summary of samples collected by the Hydrothermal Organic Geochemistry (HOG) sampler on R/V Kilo Moana (KM22-14) with ROV Jason, on dives J2_1468 through J2_1478, November 20, 2022 to December 17, 2022.  Fluid samples were collected into either 2 L or 11 L kynar bags that were acid washed (10% HCl soak overnight, followed by through rinsing, overnight Milli-Q soak, and further rinsing). Additional samples were collected by filtering fluids in situ through sterivex filters, flat filters loaded with RNA later, or copper tubes used for helium gas sampling. Partway through the expedition, a long tube was added to the intake of the sampler that reached deeper into the borehole. Samples collected after this addition recovered higher purity fluids. N.D. is no data. Table 2. Geochemical Data including pH, alkalinity, hydrolizable amino acids, free amino acids, total acetate, total formate, stable isotopes of dissolved inorganic carbon (δ13C), and stable isotopes of water (δ2H and δ18O).