@article {2939,
	title = {Revisiting the marine reservoir age in Baja California continental margin sediments using 14C and 210Pb dating},
	journal = {Quaternary Geochronology},
	volume = {66},
	year = {2021},
	month = {Jan-10-2021},
	pages = {101178},
	abstract = {Knowledge of the Marine Reservoir Effect (MRE) correction is fundamental in palaeoceanographic research to establish an accurate age-depth model for marine sedimentary records. However, during the last decades different MRE corrections have been applied in inconsistent ways for the same locality and same sediment cores, at Soledad Basin, Baja California, Mexico, creating confusion about the proper correction value of the marine reservoir effect (Delta R) to be applied. In contrast with the empirical approach previously used for assessing the Delta R value in Soledad Basin, in this study we applied an analytical approach based on the concurrent application of AMS-14C and 210Pbxs dating techniques made on sedimentary total organic carbon and foraminifera to determine new regional Delta R values from newly collected sediment cores from this site. Our results from Soledad Basin show a Delta R of 206 +/- 32 years for foraminifera and 706 +/- 42 years for organic carbon. Modeled ages using these results, and compared with those previously applied for the basin, highlight the relevance of the correct use of the local reservoir age as it can generate an offset of approximately 150 years if the other published Delta R were used. These differences can shift core chronologies by several decades and thus yield significant errors in palaeoceanographic reconstructions, which will be important to remedy in future work.},
	issn = {18711014},
	doi = {10.1016/j.quageo.2021.101178},
	url = {https://www.webofscience.com/wos/woscc/full-record/WOS:000696783400003?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864\&SID=6CdHvzZQLddFkxmd4Jp},
	author = {Treinen-Crespo, Christina and Barbara, Lo{\"\i}c and Villaescusa, Julio A. and Schmidt, Sabine and Pearson, Ann and Carriquiry, Jos{\'e} D.}
}
@article { ISI:000478786500021,
	title = {CO2-dependent carbon isotope fractionation in Archaea, Part II: The marine water column},
	journal = {GEOCHIMICA ET COSMOCHIMICA ACTA},
	volume = {261},
	year = {2019},
	month = {SEP 15},
	pages = {383-395},
	abstract = {Stable carbon isotope ratios of archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids have been proposed as a proxy to infer past changes in the carbon isotope composition (delta C-13) of dissolved inorganic carbon (DIC). The premise for paleo-delta C-13(DIC) reconstructions from GDGTs is based on observations of relatively constant delta C-13(GDGT) values in recent depositional environments. Marine Thaumarchaeota, thought to be the dominant source of GDGTs to marine sediments, fix inorganic carbon using the 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) pathway, which is specific to HCO3- as the substrate. Bicarbonate-dependent autotrophy has been the basis for predicting that the stable carbon isotopic composition of GDGTs (delta C-13(GDGT)) should vary in parallel with water column delta C-13(DIC) values, because HCO3- is by far the dominant fraction of DIC in modern seawater. However, this relationship has never been systematically tested. Here we examine the carbon isotopic composition of GDGTs from four water column profiles in the Southwest and Equatorial Atlantic Ocean. Values of delta C-13(GDGT) increase with depth in the water column, in contrast to the characteristic decrease in delta C-13(DIC) values. These divergent trends imply a decrease in the observed total biosynthetic isotope effect (epsilon(Ar)) with depth, i.e., the offset between delta(13)(DIC) and delta C-13(GDGT) is not constant. Instead, we find that values of epsilon(Ar) specifically correlate with oceanographic variables associated with extent of organic remineralization, decreasing as CO2 concentration increases. This observed relationship is consistent in both magnitude and direction with the results of an isotope flux-balance model for Thaumarchaeota that suggests epsilon(Ar) should be sensitive to growth rate (mu) and CO2 availability under conditions of atmospheric pCO(2) < 4 times the pre-anthropogenic Holocene level. Further tests of the sensitivity of epsilon(Ar) to u and CO2 in the modern marine environment will be essential to exploring the potential for a new, archaeal lipid-derived pCO(2) paleobarometer. (C) 2019 Elsevier Ltd. All rights reserved.},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2019.06.043},
	author = {Hurley, Sarah J. and Close, Hilary G. and Elling, Felix J. and Jasper, Claire E. and Gospodinova, Kalina and McNichol, Ann P. and Pearson, Ann}
}
@article {2664,
	title = {Illuminating microbial species-specific effects on organic matter remineralization in marine sediments},
	journal = {Environmental Microbiology},
	year = {2019},
	month = {Oct-12-2019},
	issn = {1462-2912},
	doi = {10.1111/1462-2920.14871},
	url = {https://apps.webofknowledge.com/InboundService.do?product=WOS\&Func=Frame\&DestFail=http\%3A\%2F\%2Fwww.webofknowledge.com\&SrcApp=search\&SrcAuth=Alerting\&SID=7Bytr67Z6qAbafBcvVL\&customersID=Alerting\&mode=FullRecord\&IsProductCode=Yes\&AlertId=ab9062f8-b111-4f95-},
	author = {Mahmoudi, Nagissa and Enke, Tim N. and Beaupr{\'e}, Steven R. and Teske, Andreas P. and Cordero, Otto X. and Pearson, Ann}
}
@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 {2462,
	title = {Sequential bioavailability of sedimentary organic matter to heterotrophic bacteria},
	journal = {Environmental Microbiology},
	year = {2017},
	month = {Oct-05-2017},
	abstract = {Aquatic sediments harbour diverse microbial communities that mediate organic matter degradation and influence biogeochemical cycles. The pool of bioavailable carbon continuously changes as a result of abiotic processes and microbial activity. It remains unclear how microbial communities respond to heterogeneous organic matrices and how this ultimately affects heterotrophic respiration. To explore the relationships between the degradation of mixed carbon substrates and microbial activity, we incubated batches of organic-rich sediments in a novel bioreactor (IsoCaRB) that permitted continuous observations of CO2 production rates, as well as sequential sampling of isotopic signatures (δ13C, Δ14C), microbial community structure and diversity, and extracellular enzyme activity. Our results indicated that lower molecular weight (MW), labile, phytoplankton-derived compounds were degraded first, followed by petroleum-derived exogenous pollutants, and finally by higher MW polymeric plant material. This shift in utilization coincided with a community succession and increased extracellular enzyme activities. Thus, sequential utilization of different carbon pools induced changes at both the community and cellular level, shifting community composition, enzyme activity, respiration rates, and residual organic matter reactivity. Our results provide novel insight into the accessibility of sedimentary organic matter and demonstrate how bioavailability of natural organic substrates may affect the function and composition of heterotrophic bacterial populations.},
	doi = {10.1111/1462-2920.13745},
	url = {http://doi.wiley.com/10.1111/1462-2920.13745http://onlinelibrary.wiley.com/wol1/doi/10.1111/1462-2920.13745/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111\%2F1462-2920.13745},
	author = {Mahmoudi, Nagissa and {\'e}, Steven R. and Steen, Andrew D. and Pearson, Ann}
}
@article { ISI:000386966700005,
	title = {IsoCaRB: A novel bioreactor system to characterize the lability and natural carbon isotopic (C-14, C-13) signatures of microbially respired organic matter},
	journal = {LIMNOLOGY AND OCEANOGRAPHY-METHODS},
	volume = {14},
	number = {{10}},
	year = {2016},
	month = {OCT},
	pages = {668-681},
	type = {Article},
	abstract = {Organic matter is the dominant pool of reduced carbon in marine and freshwater systems. Mineralization of organic matter is largely attributed to complex and diverse microbial communities that mediate degradation and ultimately yield the terminal respiratory product, carbon dioxide (CO2). The factors that constrain the lability and degradation of organic matter remain unclear, but they involve a complex interplay between structural and chemical properties of the compounds, physical properties of the matrices, and the functional potential of the microorganisms that are present. To investigate these relationships, we developed a novel bioreactor system-called Isotopic Carbon Respirometer-Bioreactor (IsoCaRB)-that permits real-time monitoring of microbial CO2 production rates and collects sequential samples of this CO2 for off-line isotopic analyses (C-13, C-14). Application of this system to organic-rich sediments from Salt Pond, MA reveals that organic matter is oxidized both abiotically and microbially, and that the pattern of microbial respiration by the native sediment community is complex, accessing different carbon substrates over the course of incubation. Isotopic measurements show modern organic matter of progressively older ages (<= ca. 50 yr) is consumed, and this material has variable origins (salt marsh grasses, terrestrial, and marine organic matter). Collectively, the IsoCaRB system provides coupled insights into the sources, ages, and inherent biological and abiotic reactivity of natural organic matter.},
	issn = {1541-5856},
	doi = {10.1002/lom3.10121},
	author = {Beaupr{\'e}, Steven R. and Mahmoudi, Nagissa and Pearson, Ann}
}
@article {490,
	title = {Origins of archaeal tetraether lipids in sediments: Insights from radiocarbon analysis RID A-6723-2009},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {72},
	year = {2008},
	note = {id: 2051; PT: J; UT: WOS:000259107700010},
	pages = {4577-4594},
	abstract = {Understanding the supply and preservation of glycerol dibiphytanyl glycerol tetraethers (GDGTs) in marine sediments helps inform their use in paleoceanography. Compound-specific radiocarbon measurements of sedimentary alkenones from multiple environments have been used to gain insight into processes that affect U-37(K{\textquoteright}) paleotemperature reconstructions. Similar analyses are warranted to investigate how analogous processes affecting GDGTs impact TEX86 paleotemperatures. Here we present radiocarbon measurements on individual GDGTs from Bermuda Rise and Santa Monica Basin sediments and discuss the results in the context of previous studies of co-depositional alkenones and foraminifera. The C-14 contents of GDGTs and planktonic foraminifera in Bermuda Rise are very similar, suggesting a local source; and TEX86-derived temperatures agree more closely with foraminiferal temperatures than do U-37(K{\textquoteright}) temperatures. In contrast, GDGTs in Santa Monica Basin are depleted in C-14 relative to both alkenones and foraminifera, and TEX86 temperatures agree poorly with known surface water values. We propose three possible factors that could explain these results: (i) GDGTs may be labile relative to alkenones during advective transport through oxic waters; (ii) archaeal production deep in the water column may contribute C-14-depleted GDGTs to sediments; and (iii) some GDGTs also may derive from sedimentary archaeal communities. Each of these three processes is likely to occur with varying relative importance depending on geographic location. The latter two may help to explain why TEX86 temperature reconstructions from Santa Monica Basin do not appear to reflect actual sea surface temperatures. Terrigenous GDGTs are unlikely to be major contributors to Bermuda Rise or Santa Monica Basin sediments, based on values of the BIT index. The results also indicate that the crenarchaeol regioisomer is governed by processes different from other GDGTs. Individual measurements of the crenarchaeol regioisomer are significantly depleted in C-14 relative to co-occurring GDGTs, indicating an alternative origin for this compound that presently remains unknown. Re-examination of the contribution of crenarchaeol regioisomer to the TEX86 index shows that it is a significant influence on the sensitivity of temperature reconstructions. (C) 2008 Elsevier Ltd. All rights reserved.},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2008.06.021},
	author = {Shah, Sunita R. and Mollenhauer, Gesine and Ohkouchi, Naohiko and Eglinton, Timothy I. and Pearson, Ann}
}
@article {2031,
	title = {Phylogenetically specific spearation of rRNA from prokaryotes for isotopic analysis},
	journal = {Marine Chemistry},
	volume = {92},
	year = {2004},
	note = {id: 1805},
	month = {2004},
	pages = {295-306},
	author = {Pearson, Ann and Sessions, Alex L. and Edwards, Katrina J. and Hayes, John M.}
}
@conference {1691,
	title = {Microscale AMS 14C Measurement at NOSAMS},
	booktitle = {16th International 14C Conference},
	year = {1998},
	note = {id: 1502},
	month = {1998},
	author = {Pearson, Ann and McNichol, Ann P. and Schneider, Robert J. and von Reden, Karl F.}
}
@conference {1692,
	title = {Microscale AMS (super <sup>14</sup>) C measurement at NOSAMS},
	volume = {40},
	year = {1998},
	note = {id: 2237; Source type: conferencepapers\&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-044438; AccNum: 1999-044438; ISSN: 0033-8222; CODEN: RACAAT},
	month = {1998},
	pages = {61-75},
	publisher = {University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA)},
	organization = {University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA)},
	address = {United States (USA)},
	abstract = {Techniques for making precise and accurate radiocarbon accelerator mass spectrometry (AMS) measurements on samples containing less than a few hundred micrograms of carbon are being developed at the NOSAMS facility. A detailed examination of all aspects of the sample preparation and data analysis process shows encouraging results. Small quantities of CO (sub 2) are reduced to graphite over cobalt catalyst at an optimal temperature of 605 degrees C. Measured (super 14) C/ (super 12) C ratios of the resulting targets are affected by machine-induced isotopic fractionation, which appears directly related to the decrease in ion current generated by the smaller sample sizes. It is possible to compensate effectively for this fractionation by measuring samples relative to small standards of identical size. Examination of the various potential sources of background (super 14) C contamination indicates that the sample combustion process is the largest contributor, adding ca. 1 mu g of carbon with a less-than-modern (super 14) C concentration.},
	keywords = {03, absolute age, accelerator mass spectroscopy, accuracy, C-14, C-14/C-12, carbon, Carbon dioxide, combustion, data processing, Geochronology, graphite, isotope fractionation, isotopes, mass spectroscopy, mathematical methods, methods, native elements, radioactive isotopes, sample preparation, size, spectroscopy, Stable isotopes},
	doi = {10.1017/S0033822200017902},
	url = {http://hdl.handle.net/10150/653650},
	author = {Pearson, Ann and McNichol, Ann P. and Schneider, Robert J. and von Reden, Karl F. and Zheng, Yan}
}
@conference {1800,
	title = {(super 14) C AMS measurements of},
	volume = {40},
	year = {1998},
	note = {id: 2239; Source type: conferencepapers\&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-044459; AccNum: 1999-044459; ISSN: 0033-8222; CODEN: RACAAT},
	month = {1998},
	pages = {247-253},
	publisher = {University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA)},
	organization = {University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA)},
	address = {United States (USA)},
	abstract = {The NOSAMS facility at Woods Hole Oceanographic Institution has started to develop and apply techniques for measuring very small samples on a standard Tandetron accelerator mass spectrometry (AMS) system with high-current hemispherical Cs sputter ion sources. Over the past year, results on samples ranging from 7 to 160 mu g C showed both the feasibility of such analyses and the present limitations on reducing the size of solid carbon samples. One of the main factors affecting the AMS results is the dependence of a number of the beam optics parameters on the extracted ion beam current. The extracted currents range from 0.5 to 10 mu A of (super 12) C (super -) for the sample sizes given above. We here discuss the setup of the AMS system and methods for reliable small-sample measurements and give the AMS-related limits to sample size and the measurement uncertainties.},
	keywords = {03, absolute age, accelerator mass spectroscopy, C-14, carbon, dilution, Geochronology, ions, isotopes, mass spectroscopy, precision, radioactive isotopes, sample preparation, spectroscopy, volume},
	author = {von Reden, Karl F. and McNichol, Ann P. and Pearson, Ann and Schneider, Robert J.}
}
