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doi:10.2204/iodp.proc.327.202.2015 Data report: dissolved and particulate organic carbon in the deep sediments of IODP Site U1363 near Grizzly Bare seamount1Huei-Ting Lin,2 Chih-Chiang Hsieh,2 James P. Cowen,2 and Michael S. Rappé3AbstractMarine sediments are a primary reservoir for the long-term storage of organic matter, and the rate of burial and oxidation of this sedimentary organic material help to regulate both atmospheric oxygen and carbon dioxide concentrations. To evaluate the impact of circulating basement fluid on the preservation of deeply buried organic carbon, sedimentary profiles of dissolved and particulate organic carbon (DOC and POC) near the sediment/basement interface were obtained from sediment coring at Site U1363 during Integrated Ocean Drilling Program Expedition 327. Sedimentary DOC increased from 0.25 mM at 1 m below the seawater/sediment interface to a maximum of 0.86 mM at mid-depth (8–11 meters below seafloor [mbsf]), before subsequently decreasing to a minimum of 0.10 mM at the sediment/basement interface (222.7 mbsf). Thus, the oceanic basement appears to be a net sink for sedimentary DOC. Sedimentary DOC and alkalinity profiles were similar and inversely mirror those of sulfate, suggesting that the buildup of DOC in sediment pore water is related to remineralization of sedimentary POC. The sedimentary POC content at Site U1363 ranged from 47 to 391 µmol-C/g, with δ13C values from –25.3‰ to –22.4‰. The total particulate nitrogen (PN) content ranged from 4.1 to 32.9 µmol-N/g, with δ15N values from 1.8‰ to 7.2‰ and a POC:PN ratio of 12 ± 2 (n = 54). No depth-specific systematic variations in POC, PN, POC:PN ratio, δ13C-POC or δ15N-PN were detected, and no significant correlations between sedimentary DOC and POC concentrations were observed.
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