@article {2615,
	title = {Microbial decomposition of marine dissolved organic matter in cool oceanic crust},
	journal = {Nature Geoscience},
	volume = {11},
	year = {2018},
	month = {Jan-05-2018},
	pages = {334 - 339},
	abstract = {Marine dissolved organic carbon (DOC) is one of the largest active reservoirs of reduced carbon on Earth. In the deep ocean, DOC has been described as biologically recalcitrant and has a radiocarbon age of 4,000 to 6,000 years, which far exceeds the timescale of ocean overturning. However, abiotic removal mechanisms cannot account for the full magnitude of deep-ocean DOC loss. Deep-ocean water circulates at low temperatures through volcanic crust on ridge flanks, but little is known about the associated biogeochemical processes and carbon cycling.
Here we present analyses of DOC in fluids from two borehole observatories installed in crustal rocks west of the Mid-Atlantic Ridge, and show that deep-ocean DOC is removed from these cool circulating fluids. The removal mechanism is isotopically selective and causes a shift in specific features of molecular composition, consistent with microbe-mediated oxidation. We suggest organic molecules with an average radiocarbon age of 3,200 years are bioavailable to crustal microbes, and that this removal mechanism may account for at least 5\% of the global loss of DOC in the deep ocean. Cool crustal circulation probably contributes to maintaining the deep ocean as a reservoir of {\textquoteright}aged{\textquoteright} and refractory DOC by discharging the surviving organic carbon constituents that are molecularly degraded and depleted in C-14 and C-13 into the deep ocean.},
	keywords = {carbon, community, deep-ocean, DISTINCT, extraction, fluid-flow, HEAT, MID-ATLANTIC RIDGE, SEAWATER, WESTERN FLANK},
	issn = {1752-0894},
	doi = {10.1038/s41561-018-0109-5},
	url = {http://www.nature.com/articles/s41561-018-0109-5http://www.nature.com/articles/s41561-018-0109-5.pdfhttp://www.nature.com/articles/s41561-018-0109-5http://www.nature.com/articles/s41561-018-0109-5.pdf},
	author = {Shah Walter, Sunita R. and Jaekel, Ulrike and Osterholz, Helena and Fisher, Andrew T. and Huber, Julie A. and Pearson, Ann and Dittmar, Thorsten and Girguis, Peter R.}
}
@article {1936,
	title = {Bioreactivity of estuarine dissolved organic matter: A combined geochemical and microbiological approach},
	journal = {Limnology and Oceanography},
	volume = {51},
	year = {2006},
	note = {040scTimes Cited:39
Cited References Count:32
},
	month = {Jan},
	pages = {94-100},
	abstract = {An integrated multidisciplinary study utilizing geochemical and microbial ecological approaches was conducted to characterize the origins, chemical nature, and quantities of dissolved and particulate organic matter (OM) utilized by heterotrophic bacteria in a temperate estuary. C: N, stable isotope (delta C-13), and lipid biomarker analyses revealed differences in the inferred reactivity of autochthonous versus allochthonous OM sources. Isotopic comparison of OM size fractions and bacterial nucleic acids suggests that high-molecular-weight dissolved OM (DOM) is consistently linked to bacterial biomass synthesis along the estuarine salinity gradient. Polyunsaturated fatty acids (as percent of total fatty acids, FA) were a reliable predictor of DOM decomposition in bioassays, thus providing an indicator directly linking DOM reactivity to its composition. Significant positive correlations between FA diagnostic of bacterial sources and lipid biomarker compounds diagnostic of planktonic origin indicate a systematic bacterial response to autochthonous DOM sources along the estuarine continuum. These findings further suggest that, although the geochemical signature of algal-derived OM in the dissolved phase may appear quantitatively insignificant, this fraction may nevertheless represent a principal source of bioreactive OM to heterotrophic bacteria in estuarine waters.},
	keywords = {acids, bacteria, bay, bioavailability, carbon-isotope analysis, extraction, food webs, sediments},
	isbn = {0024-3590},
	doi = {10.4319/lo.2006.51.1.0094},
	author = {McCallister, S. L. and Bauer, J. E. and Canuel, E. A.}
}
