@article{liu_kuehl_pierce_williams_blair_harris_aung_aye_2020, title={Fate of Ayeyarwady and Thanlwin Rivers Sediments in the Andaman Sea and Bay of Bengal}, volume={423}, ISSN={["1872-6151"]}, DOI={10.1016/j.margeo.2020.106137}, abstractNote={Collectively, the modern Ayeyarwady (Irrawaddy) and Thanlwin (Salween) rivers deliver >600 Mt/yr of sediment to the sea. To understand the fate of Ayeyarwady and Thanlwin river-derived sediments to the sea, we conducted a 14-day geophysical and geological survey in the northern Andaman Sea and eastern Bay of Bengal in December 2017. Overall, ~1500-km of high-resolution Chirp-sonar profiles and 30 sediment cores from the shelf were acquired. This paper presents the results of the processed high-resolution profiles together with sediment analyses. Our findings indicate: 1) There is little modern sediment accumulating on the shelf immediately off the Ayeyarwady River mouths. In contrast, a major mud wedge with a distal depocenter, up to 60 m in thickness, has been deposited seaward in the Gulf of Martaban, extending to ~130 m water depth into the Martaban Depression. Further, 2) There is no evidence showing that modern sediment has accumulated or is transported into the Martaban Canyon; 3) There is a mud drape/blanket wrapping around the narrow western Myanmar Shelf in the eastern Bay of Bengal. The thickness of the mud deposit is up to 20 m nearshore and gradually thins to the slope at −300 m water depth, and likely escapes into the deep Andaman Trench; 4) The estimated total amount of Holocene sediments deposited offshore is ~1290 × 109 tons. If we assume this has mainly accumulated since the middle Holocene highstand (~6000 yr BP) like other major deltas, the historical annual mean depositional flux on the shelf would be 215 Mt/yr, which is equivalent to ~35% of the modern Ayeyarwady-Thanlwin rivers derived sediments; 5) Unlike other large river systems in Asia, such as the Yangtze and Mekong, this study indicates a bi-directional transport and depositional pattern controlled by the local currents that are influenced by tides, and seasonally varying monsoons winds and waves. Organic carbon biomarkers and isotope compositions show a gradual changing pattern with the along-shelf transport from the river to the Gulf of Martaban in the east and to the Bay of Bengal in the west.}, journal={MARINE GEOLOGY}, author={Liu, J. Paul and Kuehl, Steven A. and Pierce, Austin C. and Williams, Joshua and Blair, Neal E. and Harris, Courtney and Aung, Day Wa and Aye, Yin Yin}, year={2020}, month={May} }
 @article{aller_blair_brunskill_2008, title={Early diagenetic cycling, incineration, and burial of sedimentary organic carbon in the central Gulf of Papua (Papua New Guinea)}, volume={113}, ISSN={["2169-9011"]}, DOI={10.1029/2006jf000689}, abstractNote={The clinoform complex of the Gulf of Papua represents a major deltaic system in Oceania. Two seasons largely control seafloor dynamics and sedimentary C cycling: the relatively quiescent NW monsoon, and the SE trades, characterized by remobilization and reoxidation of topset deposits. Surface sediments (∼20 cm) are reactive with ΣCO2 production fluxes ∼35–42 mmol m−2 d−1 at mangrove channel and topset sites during the monsoon, and ∼10–20 mmol m−2 d−1 on the foreset‐bottomset (>40 m). Fluxes decrease by a factor of ∼0.3 on the topset during the transition period and trades. The 13,14C isotopic compositions of pore water ΣCO2 reveal diagenetic fractionation, with dominant utilization of young (Δ14C = 1.4–31.1‰), terrestrial C substrates inshore (channels, topset δ13C = −29 to −25‰) and a progressive increase of young marine C sources seaward (outer topset, foreset; bottomset δ13C = −22.2 to −19.5). Remineralization patterns of terrestrial and marine Corg demonstrate cross‐shelf exchange. Multiple tracers show that a suboxic, mobile mud layer, ∼10–60 cm thick (usually ∼10–30 cm), characterizes the central gulf topset and Umuda Valley off the Fly River and unconformably overlies methanic deposits releasing old ΣCO2 (Δ14C = −159 to −229‰). Residual terrestrial Corg delivered to the bioturbated foreset continues to be remineralized slowly, generating ΣCO2 having net Δ14C = −270 within sediments deposited 100–200 years ago. The reactivity of Corg below ∼0.5 m in the foreset is ∼10–20 times lower than expected based on accumulation rates, reflecting loss of >50% of sedimentary Corg on the topset, which functions as a suboxic incinerator.}, number={F1}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE}, author={Aller, Robert C. and Blair, Neal E. and Brunskill, Gregg J.}, year={2008}, month={Jan} }
 @article{aller_blair_2006, title={Carbon remineralization in the Amazon-Guianas tropical mobile mudbelt: A sedimentary incinerator}, volume={26}, DOI={10.1016/j.csr.2006.07.016}, abstractNote={The Amazon River spawns a vast mobile mudbelt extending ∼1600 km from the equator to the Orinoco delta. Deposits along the Amazon–Guianas coastline are characterized by some of the highest Corg remineralization rates reported for estuarine, deltaic, or shelf deposits, however, paradoxically, except where stabilized by mangroves or intertidal algal mats, they are usually suboxic and nonsulfidic. A combination of tides, wind-driven waves, and coastal currents forms massive fluid muds and mobile surface sediment layers ∼0.5–2 m thick which are dynamically refluxed and frequently reoxidized. Overall, the seabed functions as a periodically mixed batch reactor, efficiently remineralizing organic matter in a gigantic sedimentary incinerator of global importance. Amazon River material entering the head of this dynamic dispersal system carries an initial terrestrial sedimentary Corg loading of ∼ 0.7 mg C m−2 particle surface area. Total Corg loading is lowered to ∼ 0.2 mg C m−2 in the proximal delta topset, ∼60–70% of which remains of terrestrial origin. Loading decreases further to 0.12–0.14 mg C m−2 (∼60% terrestrial) in mudbanks ∼600 km downdrift along French Guiana, values comparable to those found in the oligotrophic deepsea. DOC/ΣCO2 ratios in pore waters of French Guiana mudbanks indicate that >90% of metabolized organic substrates are completely oxidized. Within the Amazon delta topset at the head of the dispersal system, both terrestrial and marine organic matter contribute substantially to early diagenetic remineralization, although reactive marine substrate dominates (∼60–70%). The conditional rate constant for terrestrial Corg in the delta topset is ∼0.2 a−1. As sedimentary Corg is depleted during transit, marine sources become virtually the exclusive substrate for remineralization except very near the mangrove shoreline. The δ13C and Δ14C values of pore water ΣCO2 in mudbanks demonstrate that the primary source of remineralized organic matter within ∼1 km of shore is a small quantity of bomb signature marine plankton (+80‰). Thus, fresh marine organic material is constantly entrained into mobile deposits and increasingly drives early diagenetic reactions along the transit path. Relatively refractory terrestrial Corg is lost more slowly but steadily during sedimentary refluxing and suboxic diagenesis. Amazon Fan deposits formed during low sea level stand largely bypassed this suboxic sedimentary incinerator and stored material with up to ∼3X the modern high stand inner shelf Corg load (Keil et al., 1997b. Proceedings of the Ocean Drilling Program, Scientific Results. Vol. 155. pp. 531–537). Sedimentary dynamics, including frequency and magnitude of remobilization, and the nature of dispersal systems are clearly key controls on diagenetic processes, biogeochemical cycling, and global C storage along the continental margins.}, number={17-18}, journal={Continental Shelf Research}, author={Aller, R. C. and Blair, N. E.}, year={2006}, pages={2241–2259} }
 @article{leithold_blair_perkey_2006, title={Geomorphologic controls on the age of particulate organic carbon from small mountainous and upland rivers}, volume={20}, ISSN={["1944-9224"]}, DOI={10.1029/2005gb002677}, abstractNote={To assess the role that erosion processes play in governing the character of particulate organic carbon (POC) discharged from small mountainous and upland rivers, a suite of watersheds from Oregon, California, and New Zealand was investigated. The rivers share similar geology, tectonic setting, and climate, but have sediment yields that range over 3 orders of magnitude. The 14C age of the POC loads is highly correlated with sediment yield. Carbon isotope mass balances reveal that the rivers carry bimodal mixtures of modern‐plant‐ and ancient‐rock‐derived OC. At lower yields, modern plant OC dominates the material delivered to the river by sheetwash and shallow landsliding. With increasing yield, a progressively larger part of the POC is contributed directly from bedrock erosion via deep gully incision. Our results support the inference that active margin watersheds are important sources of aged POC to the ocean.}, number={3}, journal={GLOBAL BIOGEOCHEMICAL CYCLES}, author={Leithold, Elana L. and Blair, Neal E. and Perkey, David W.}, year={2006}, month={Sep} }
 @article{savidge_blair_2005, title={Intramolecular carbon isotopic composition of monosodium glutamate: Biochemical pathways and product source identification}, volume={53}, ISSN={["1520-5118"]}, DOI={10.1021/jf040200k}, abstractNote={Monosodium glutamate (MSG) obtained as trade samples from several manufacturers was studied to determine the range of its intramolecular 13C/12C composition. Although the carbon isotopic composition of the total MSG molecule did not differ among manufacturers in most instances, significant differences were observed in the isotopic composition of the alpha-carboxyl carbon, suggesting that different proprietary strains of industrial microorganisms or MSG purification methods may impart unique isotopic fingerprints upon their products. The 13C depletion of the alpha-carboxyl carbon relative to the rest of the molecule helps constrain the identity of the potential anapleurotic carboxylating enzymes responsible for its fixation.}, number={2}, journal={JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY}, author={Savidge, WB and Blair, NE}, year={2005}, month={Jan}, pages={197–201} }
 @misc{leithold_perkey_blair_creamer_2005, title={Sedimentation and carbon burial on the northern California continental shelf: the signatures of land-use change}, volume={25}, ISSN={["1873-6955"]}, DOI={10.1016/j.csr.2004.09.015}, abstractNote={The burial of organic carbon (OC) on continental margins is strongly coupled to the supply and accumulation of inorganic mineral particles. It follows that carbon burial on the margins should be impacted by changes in riverine sediment delivery, yet these impacts have not been well documented. In this study, an ∼2000-year record of sedimentation and carbon burial on the continental shelf offshore from the Eel River in northern California was examined. The record reveals a 6–11-fold increase in the rate of sediment accumulation on the mid-shelf beginning about 1955, and a concomitant decrease in grain size and increase in flood-layer preservation. At the same time, the age of buried wood fragments abruptly decreased and their stable carbon isotopic composition became enriched in 13C. We argue that these changes can be explained largely as the result of altered land use in the Eel watershed during the past century and its impacts on shelf sediment dispersal processes. Sedimentary OC on the Eel shelf consists primarily of discrete wood fragments associated with coarse-silt- and sand-sized particles, and of organic matter strongly bound to clay-sized mineral grains. The clay fraction is a particularly sensitive recorder of environmental change in the Eel system. Above the 1955 horizon, the clay fraction shows an abrupt decrease in OC concentration and loading (OC content normalized to particle surface area) attendant with the increased accumulation rate. Kerogen carbon constitutes a relatively constant proportion of the clay-associated OC throughout the ∼2000-year record. Increases in mass wasting and input of bedrock material following the onset of intensive industrial logging in the Eel watershed may have resulted in a lower loading of terrestrial plant OC in the clay fraction deposited after 1955 as suggested by isotopic mass balance calculations. The Eel River is representative of small mountainous watersheds worldwide that deliver a major portion of the sediment and carbon flux to the margins and that have been strongly impacted by land-use change during the past century. Our results suggest that such changes leave a distinctive mark in both the sedimentological and geochemical records preserved offshore.}, number={3}, journal={CONTINENTAL SHELF RESEARCH}, author={Leithold, EL and Perkey, DW and Blair, NE and Creamer, TN}, year={2005}, month={Feb}, pages={349–371} }
 @article{aller_blair_2004, title={Early diagenetic remineralization of sedimentary organic C in the Gulf of Papua deltaic complex (Papua New Guinea): Net loss of terrestrial C and diagenetic fractionation of C isotopes}, volume={68}, ISSN={["1872-9533"]}, DOI={10.1016/j.gca.2003.10.028}, abstractNote={Oceania supplies ∼40% of the global riverine flux of organic carbon, approximately half of which is injected onto broad continental shelves and processed in shallow deltaic systems. The Gulf of Papua, on the south coast of the large island of New Guinea, is one such deltaic clinoform complex. It receives ∼4 Mt yr−1 particulate terrestrial organic carbon with initial particle Corg loading ∼0.7 mg m−2. Corg loading is reduced to ∼0.3 mg m−2 in the topset-upper foreset zones of the delta despite additional inputs of mangrove and planktonic detritus, and high net sediment accumulation rates of 1–4 cm yr−1. Carbon isotopic analyses (δ13C, Δ14C) of ΣCO2 and Corg demonstrate rapid (<100 yr) remineralization of both terrestrial (δ13C <−28.6) and marine Corg (δ13C ∼−20.5) ranging in average age from modern (bomb) (Δ14C ∼60) to ∼1000 yr (Δ14C ∼−140). Efficient and rapid remineralization in the topset-upper foreset zone is promoted by frequent physical reworking, bioturbation, exposure, and reoxidation of deposits. The seafloor in these regions, particularly <20 m, apparently functions as a periodically mixed, suboxic batch reactor dominated by microbial biomass. Although terrestrial sources can be the primary metabolic substrates at inshore sites, relatively young marine Corg often preferentially dominates pore water ΣCO2 relative to bulk Corg in the upper foreset. Thus a small quantity of young, rapidly recycled marine organic material is often superimposed on a generally older, less reactive terrestrial background. Whereas the pore water ΣCO2 reflects both rapidly cycled marine and terrestrial sources, terrestrial material dominates the slower overall net loss of Corg from particles in the topset-upper foreset zone (i.e. recycled marine Corg leaves little residue). Preferential utilization of Corg subpools and diagenetic fractionation of C isotopes supports the reactive continuum model as a conceptual basis for net decomposition kinetics. Early diagenetic fractionation of C isotopes relative to the bulk sedimentary Corg composition can produce changes in 14C activity independent of radioactive decay. In the Gulf of Papua topset-upper foreset, Δ14C of pore water ΣCO2 averaged ∼ 300‰ greater than Corg sediment between ∼1–3 m depth in deposits. Diagenetic fractionation and decomposition aging of sedimentary Corg compromises simple application of 14C for determination of sediment accumulation rates in diagenetically reactive deposits.}, number={8}, journal={GEOCHIMICA ET COSMOCHIMICA ACTA}, author={Aller, RC and Blair, NE}, year={2004}, month={Apr}, pages={1815–1825} }
 @article{blair_leithold_aller_2004, title={From bedrock to burial: the evolution of particulate organic carbon across coupled watershed-continental margin systems}, volume={92}, ISSN={["1872-7581"]}, DOI={10.1016/j.marchem.2004.06.023}, abstractNote={Deltas sequester nearly half of the organic carbon (OC) buried in the marine environment. The composition of the buried organic matter reflects both watershed and seabed processes. A conceptual model is presented that describes the evolution of particulate organic carbon (POC) as it travels from its terrestrial source to its burial at sea. Alterations to the POC occur primarily in bioactive reservoirs, such as soils and the surface mixed layer (SML) of the seabed, where new organic matter can be added and older material degraded. Bypassing or rapid passage through the reservoirs is a key parameter because it avoids change. The Eel River of northern California and the Amazon River systems illustrate the importance of reservoir transit time and storage in determining the character of POC delivered to the continental margin. The Eel exemplifies a bypass system. Mass-wasting processes on land deliver unaltered bedrock along with OC derived from extant vegetation directly to the river channel without significant storage in soils. Rapid burial on the shelf occurs as a result of flood events. As a consequence, the buried material appears to be a simple mixture of carbon derived from kerogen (bedrock C), and modern terrestrial and marine sources. This is predicted to be a characteristic of the many similar short rivers on active margins that supply >40% of the fluvial sediment to the world's ocean. Extensive storage and processing of OC in lowland soils is a characteristic of the large Amazon watershed. Upland POC compositions are either overprinted or replaced by lowland sources. Upon delivery to the shelf, over half of the riverine POC is lost as a result of residence in sediment layers that are periodically reworked over time scales of days to months. The addition of fresh reactive marine OC, exposure to oxygen, and the regeneration of metal oxidants during resuspension events fuel the oxidation of the riverine organic matter. The nature of the watershed-shelf processes likely produce a complex mixture of organics possessing a continuum of ages and reactivities. The model illustrates the need to develop tools to measure residence times of particles in the various reservoirs so that the behavior of POC can be calibrated as it moves through a sedimentary system. The ultimate goal is to be able to use the organic geochemistry of soils and sediments to quantitatively infer the history of processes that determine both the composition and amount of POC present in different depositional environments.}, number={1-4}, journal={MARINE CHEMISTRY}, author={Blair, NE and Leithold, EL and Aller, RC}, year={2004}, month={Dec}, pages={141–156} }
 @article{savidge_blair_2004, title={Patterns of intramolecular carbon isotopic heterogeneity within amino acids of autotrophs and heterotrophs}, volume={139}, ISSN={["0029-8549"]}, DOI={10.1007/s00442-004-1500-z}, abstractNote={A survey of the intramolecular C isotopic composition of a variety of organisms was conducted to investigate the potential of intramolecular isotopic measurements as a tracer of biological or geochemical processes. Based on a consideration of inorganic C sources and enzymatic fractionations, contrasting predictions were made for the relative (13)C enrichments of the alpha-carboxyl carbons fixed by the anapleurotic (beta)-carboxylation pathway during amino acid synthesis by photoautotrophs and heterotrophs. To test the model predictions, the stable C isotopic compositions of the acid hydrolyzable C fraction, the total amino acid alpha-carboxyl C fraction and the alpha-carboxyl C of glutamate from a variety of autotrophic and heterotrophic organisms were compared. The relative (13)C enrichments of carboxyl carbons in the bulk amino acid fraction and in glutamate conformed qualitatively to model predictions. Macroalgal taxa possessed a significantly less enriched carboxyl C fraction than did either C3 or C4 vascular plants, indicating the presence of a different beta-carboxylation pathway operating in these organisms. In most multicellular heterotrophs, the isotopic composition of the amino acid carboxyl carbons closely resembled that of their food sources. Amino acids are apparently assimilated into tissue proteins directly from their diets without significant metabolic modification. However, shifts in the isotopic composition of the carboxyl C fractions in some organisms were detected that were consistent with the occurrence of significant resynthesis of amino acids from non-amino acid precursors. Comparison of plant leaves and roots provided evidence of environmentally controlled assimilate partitioning. Intramolecular isotopic measurements of biological molecules provide unique insights into the origins and transformations of bio-molecules.}, number={2}, journal={OECOLOGIA}, author={Savidge, WB and Blair, NE}, year={2004}, month={Apr}, pages={178–189} }
 @article{savidge_blair_2004, title={Seasonal and within-plant gradients in the intramolecular carbon isotopic composition of amino acids of Spartina alterniflora}, volume={308}, ISSN={["1879-1697"]}, DOI={10.1016/j.jembe.2004.02.010}, abstractNote={Autotrophy and heterotrophy create different patterns of carbon flux through the central metabolic pathway. One consequence of these different fluxes is that the α-carboxyl carbon of amino acids is derived from different carbon sources and has a different isotopic composition under autotrophic and heterotrophic conditions. In Spartina alterniflora, a C4 grass and a common and ecologically important component of coastal ecosystems, the isotopic composition of bulk acid hydrolyzable carbon and total amino acid carboxyl carbon were compared over a seasonal cycle. The isotopic composition of plants varied significantly between aboveground and below ground tissues, and the δ13C of both hydrolyzable organic carbon and total amino acid carboxyl carbon showed significant variation among seasons. The isotopic heterogeneity within amino acids was used to infer seasonal changes in source/sink relationships for amino acid carbon among plant organs. Comparison of the intramolecular isotope data for Spartina and C3 freshwater marsh plants indicates that the patterns and processes inferred for Spartina are not unique to this taxon.}, number={2}, journal={JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY}, author={Savidge, WB and Blair, NE}, year={2004}, month={Sep}, pages={151–167} }
 @article{blair_leithold_ford_peeler_holmes_perkey_2003, title={The persistence of memory: The fate of ancient sedimentary organic carbon in a modern sedimentary system}, volume={67}, ISSN={["1872-9533"]}, DOI={10.1016/S0016-7037(02)01043-8}, abstractNote={The cycle of organic carbon burial and exhumation moderates atmospheric chemistry and global climate over geologic timescales. The burial of organic carbon occurs predominantly at sea in association with clay-sized particles derived from the erosion of uplifted continental rocks. It follows that the history of the fine-grained particles on land may bear on the nature of the organic carbon buried. In this study, the evolution of clay-associated organic matter was followed from bedrock source to the seabed in the Eel River sedimentary system of northern California using natural abundance 13C and 14C tracers. Approximately half of the fine-grained organic carbon delivered to the shelf is derived from ancient sedimentary organic carbon found in the uplifted Mesozoic-Tertiary Franciscan Complex of the watershed. The short residence time of friable soils on steep hill slopes, coupled with rapid sediment accumulation rates on the shelf-slope, act to preserve the ancient organic carbon. A comparable quantity of modern organic carbon is added to particles in the watershed and on the shelf and slope. The bimodal mixture of ancient and modern C in soils and sediments may be characteristic of many short, mountainous rivers. If the Eel River chemistry is typical of such rivers, more than 40 Tg of ancient organic C may be delivered to the world’s oceans each year. A flux of that magnitude would have a significant influence on marine and global C-cycles.}, number={1}, journal={GEOCHIMICA ET COSMOCHIMICA ACTA}, author={Blair, NE and Leithold, EL and Ford, ST and Peeler, KA and Holmes, JC and Perkey, DW}, year={2003}, month={Jan}, pages={63–73} }
 @article{gould_blair_reid_rennie_lopez_micinski_2002, title={Bacillus thuringiensis-toxin resistance management: Stable isotope assessment of alternate host use by Helicoverpa zea}, volume={99}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.242382499}, abstractNote={
            Data have been lacking on the proportion of
            Helicovera zea
            larvae that develop on noncotton host plants that can serve as a refuge from selection pressure for adaptation to transgenic cotton varieties that produce a toxin from the bacterium
            Bacillus thuringiensis
            . We found that individual
            H. zea
            moths that develop as larvae on cotton and other plants with C
            3
            physiology have a different ratio of
            13
            C to
            12
            C than moths that develop on plants with C
            4
            physiology, such as corn. We used this finding in determining the minimum percentage of moths that developed on noncotton hosts in two cotton-growing areas. Our results indicate that local corn can serve as a refuge for
            H. zea
            in midsummer. Our results contrast dramatically with the prevailing hypothesis that the large majority of late-season moths are produced from larvae feeding on cotton, soybean, and other C
            3
            plants. Typically, <50% of moths captured in August through October have isotope ratios indicative of larval feeding on C
            3
            plants. In one October sample, 100% of the moths originated from C
            4
            hosts even though C
            4
            crops were harvested at least 1 mo earlier, and no common wild C
            4
            hosts were available. These findings support other research indicating that many late-season
            H. zea
            moths captured in Louisiana and Texas are migrants whose larvae developed on corn in more northern locations. Our isotope data on moths collected in Texas early in the season indicate that the majority of overwintering
            H. zea
            do not originate from cotton-feeding larvae and may be migrants from Mexico. Non-Bt corn in Mexico and the U.S. corn belt appears to serve as an important refuge for
            H. zea
            .
          }, number={26}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Gould, F and Blair, N and Reid, M and Rennie, TL and Lopez, J and Micinski, S}, year={2002}, month={Dec}, pages={16581–16586} }
 @article{demaster_thomas_blair_fornes_plaia_levin_2002, title={Deposition of bomb (14)C in continental slope sediments of the Mid-Atlantic Bight: assessing organic matter sources and burial rates}, volume={49}, ISSN={["0967-0645"]}, DOI={10.1016/S0967-0645(02)00134-0}, abstractNote={As part of the Ocean Margins Program (OMP), organic carbon 14C measurements have been made on benthic fauna and kasten core sediments from the North Carolina continental slope. These analyses are used to evaluate the nature and burial flux of organic matter in the OMP study area off Cape Hatteras. Despite the fact that surface sediment 14C contents ranged from −41 to −215 per mil, the benthic fauna (primarily polychaetes) all contained significant amounts of bomb-14C (body tissue 14C contents ranging from +20 to +82 per mil). Bomb-14C clearly is reaching the seabed on the North Carolina slope, and the labile planktonic material carrying this signal is a primary source of nutrition to the benthic ecosystem. The enrichment of 14C in benthic faunal tissue relative to the 14C content of bulk surface-sediment organic matter (a difference of ∼150 per mil) is attributed to a combination of particle selection and selective digestive processes. Organic carbon burial rates from 12 stations on the North Carolina slope varied from 0.02 to 1.7 mol of C m−2 yr−1, with a mean value of 0.7 mol of C m−2 yr−1. The accumulation of organic matter on the upper slope accounts for <1% of the primary production in the entire continental margin system. The North Carolina margin was deliberately selected because of its potential for offshore transport and high sediment deposition rates, and even in this environment, burial of organic carbon accounts for a very small fraction of the primary production occurring in surface waters.}, number={20}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={DeMaster, DJ and Thomas, CJ and Blair, NE and Fornes, WL and Plaia, G and Levin, LA}, year={2002}, pages={4667–4685} }
 @article{thomas_blair_alperin_demaster_jahnke_martens_mayer_2002, title={Organic carbon deposition on the North Carolina continental slope off Cape Hatteras (USA)}, volume={49}, ISSN={["1879-0100"]}, DOI={10.1016/S0967-0645(02)00135-2}, abstractNote={The continental slope off Cape Hatteras, NC is a region of high sediment accumulation and organic matter deposition. Sediment accumulation rates range from 3 to 151 cm kyr−1. Organic carbon deposition rates are 5–13 moles C m−2 yr−1, the highest reported for the slope off the eastern US. Burial efficiencies are 3–40%. The organic matter deposited is marine in origin and a mix of old and young particles. High organic carbon deposition rates support remineralization throughout the upper 2–3 m of sediment. Deep bioirrigation to depths of 60–100 cm within the seabed affects the biogeochemistry of the sediments by extending the zone of sulfate reduction and by steepening DIC porewater gradients through the non-local exchange of porewater. Stable and radiocarbon isotope mixing curves for porewater dissolved inorganic carbon (DIC) indicate that the dominant source of DIC accumulating in the upper 2–3 m of the seabed is of nearly uniform δ13C (−21.10‰) and Δ14C (−546‰).}, number={20}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, publisher={Elsevier BV}, author={Thomas, CJ and Blair, NE and Alperin, MJ and DeMaster, DJ and Jahnke, RA and Martens, CS and Mayer, L}, year={2002}, pages={4687–4709} }
 @article{thomas_blair_2002, title={Transport and digestive alteration of uniformly C-13-labeled diatoms in mudflat sediments}, volume={60}, ISSN={["1543-9542"]}, DOI={10.1357/002224002762231205}, abstractNote={Uniformly 13 C-labeled diatoms were used to elucidate the effect deposit feeders have on the distribution and composition of phytodetritus within the seabed. Mudflat infauna contained in microcosms reacted quickly to the emplacement of labeled diatoms onto the sediment-water interface by moving the phytodetritus nonlocally during feeding and hoeing activities. Although redistribution of tracer was rapid, not all infauna exposed to the tracer ingested it. Using four species of deposit-feeding annelids that had ingested the 13 C-labeled phytodetritus during the microcosm experiment, molecular-level, digestive alterations of 13 C-labeled diatoms were documented. Fecal material produced by the deposit feeders had 13 C amino acid signatures distinctly different from that of the diatom. Alterations in the amino acid composition of the diatom were correlated to the gut morphology and digestive physiology of the polychaete taxa.}, number={3}, journal={JOURNAL OF MARINE RESEARCH}, publisher={Journal of Marine Research/Yale}, author={Thomas, CJ and Blair, NE}, year={2002}, month={May}, pages={517–535} }
 @article{leithold_blair_2001, title={Watershed control on the carbon loading of marine sedimentary particles}, volume={65}, ISSN={["0016-7037"]}, DOI={10.1016/S0016-7037(01)00593-2}, abstractNote={Previous investigations of the factors governing organic carbon burial on continental margins have pointed toward the important, apparently protective association of carbon with mineral particles. These studies have also revealed dramatic transformations of carbon-particle relationships at the land-sea interface. Riverine particles in some settings lose a large portion of their loads of sorbed terrestrial carbon upon discharge to the ocean and gradually reload to similar levels with marine carbon. The Eel River in northern California and the adjacent continental shelf were selected as an ideal system to investigate the rates of these processes. The river is episodically subject to large floods, and the shelf stratigraphy preserves a record of the resultant large pulses of sediment and carbon input to the marine environment. Carbon isotopic, carbon to nitrogen, and carbon to surface area ratios of particles in flood deposits were expected to reflect the rapid unloading of terrestrial carbon from discharged particles, whereas nonflood sediments that have accumulated at slower rates on the shelf were expected to carry higher loads of marine carbon. Our results indicate, however, that particles on the Eel shelf have retained their loads of terrigenous carbon, and that a significant portion of the particle-sorbed carbon buried on the shelf is kerogen derived from the Mesozoic-Tertiary Franciscan Complex. We hypothesize that rates of uplift and mass wasting in the Eel watershed and rates of particle delivery to and burial on the continental shelf, are so rapid that kerogen is not completely oxidized and is recycled instead. The loading of carbon on clay-sized particles delivered to the shelf, moreover, is dependent on river discharge and may reflect the relative importance of different mass wasting processes during precipitation events of varying intensity. The Eel River system is likely to be representative of other small, mountainous rivers and indicates that processes on land may play an important role in governing the amount and character of carbon being buried on the continental margins.}, number={14}, journal={GEOCHIMICA ET COSMOCHIMICA ACTA}, author={Leithold, EL and Blair, NE}, year={2001}, month={Jul}, pages={2231–2240} }
 @article{alperin_martens_albert_suayah_benninger_blair_jahnke_1999, title={Benthic fluxes and porewater concentration profiles of dissolved organic carbon in sediments from the North Carolina continental slope}, volume={63}, ISSN={["0016-7037"]}, DOI={10.1016/S0016-7037(99)00032-0}, abstractNote={Numerous studies of marine environments show that dissolved organic carbon (DOC) concentrations in sediments are typically tenfold higher than in the overlying water. Large concentration gradients near the sediment–water interface suggest that there may be a significant flux of organic carbon from sediments to the water column. Furthermore, accumulation of DOC in the porewater may influence the burial and preservation of organic matter by promoting geopolymerization and/or adsorption reactions. We measured DOC concentration profiles (for porewater collected by centrifugation and “sipping”) and benthic fluxes (with in situ and shipboard chambers) at two sites on the North Carolina continental slope to better understand the controls on porewater DOC concentrations and quantify sediment–water exchange rates. We also measured a suite of sediment properties (e.g., sediment accumulation and bioturbation rates, organic carbon content, and mineral surface area) that allow us to examine the relationship between porewater DOC concentrations and organic carbon preservation. Sediment depth-distributions of DOC from a downslope transect (300–1000 m water depth) follow a trend consistent with other porewater constituents (ΣCO2 and SO42−) and a tracer of modern, fine-grained sediment (fallout Pu), suggesting that DOC levels are regulated by organic matter remineralization. However, remineralization rates appear to be relatively uniform across the sediment transect. A simple diagenetic model illustrates that variations in DOC profiles at this site may be due to differences in the depth of the active remineralization zone, which in turn is largely controlled by the intensity of bioturbation. Comparison of porewater DOC concentrations, organic carbon burial efficiency, and organic matter sorption suggest that DOC levels are not a major factor in promoting organic matter preservation or loading on grain surfaces. The DOC benthic fluxes are difficult to detect, but suggest that only 2% of the dissolved organic carbon escapes remineralization in the sediments by transport across the sediment-water interface.}, number={3-4}, journal={GEOCHIMICA ET COSMOCHIMICA ACTA}, author={Alperin, MJ and Martens, CS and Albert, DB and Suayah, IB and Benninger, LK and Blair, NE and Jahnke, RA}, year={1999}, month={Feb}, pages={427–448} }
 @article{fornes_demaster_levin_blair_1999, title={Bioturbation and particle transport in Carolina slope sediments: A radiochemical approach}, volume={57}, ISSN={["1543-9542"]}, DOI={10.1357/002224099321618245}, abstractNote={In situ tracer experiments investigated short-term sediment mixing processes at two Carolina continental margin sites (water depth = 850 m) characterized by different organic C fluxes, 234 Th mixing coefficients (D b ) and benthic assemblages. Phytoplankton, slope sediment, and sand-sized glass beads tagged with 210 Pb, 113 Sn, and 228 Th, respectively, were placed via submersible at the sediment-water interface at both field sites (Site I off Cape Fear, and Site III off Cape Hatteras). Experimental plots were sampled at 0, 1.5 days, and 90 days after tracer emplacement to examine short-term, vertical transport. Both sites are initially dominated by nonlocal mixing. Transport to the bottom of the surface mixed layer at both sites occurs more rapidly than 234 Th-based D b values predict; after 1.5 days, tagged particles were observed 5 cm below the sediment-water interface at Site I and 12 cm below at Site III. Impulse tracer profiles after 90 days at Site III exhibit primarily diffusive distributions, most likely due to a large number of random, nonlocal mixing events. The D b values determined from 90-day particle tagging experiments are comparable to those obtained from naturally occurring 234 Th profiles (∼100-day time scales) from nearby locations. The agreement between impulse tracer mixing coefficients and steady-state natural tracer mixing coefficients suggests that the diffusive analogue for bioturbation on monthly time scales is a realistic and useful approach. Tracer profiles from both sites exhibit some degree of particle selective mixing, but the preferential transport of the more labile carbon containing particles only occurred 30% of the time. Consequently, variations in the extent to which age-dependent mixing occurs in marine sediments may depend on factors such as faunal assemblage and organic carbon flux.}, number={2}, journal={JOURNAL OF MARINE RESEARCH}, author={Fornes, WL and DeMaster, DJ and Levin, LA and Blair, NE}, year={1999}, month={Mar}, pages={335–355} }
 @article{levin_blair_martin_demaster_plaia_thomas_1999, title={Macrofaunal processing of phytodetritus at two sites on the Carolina margin: in situ experiments using C-13-labeled diatoms}, volume={182}, ISSN={["0171-8630"]}, DOI={10.3354/meps182037}, abstractNote={Tracer experiments using 13 C-labeled diatoms Thalassiosira pseudonana were carried out at two 850 m sites (I off Cape Fear and III off Cape Hatteras) on the North Carolina, USA, slope to examine patterns of macrofaunal consumption of fresh phytodetritus. Experiments examined the influence of taxon, feeding mode, body size and vertical position within the sediment column on access to surficial organic matter. δ 13 C measurements were made on macrofaunal metazoans and agglutinating protozoans from background sediments and from sediment plots in which 13 C-labeled diatoms were deposited and then sampled 0.3 h, 1 to 1.5 d, 3 mo and 14 mo later. Significant between-site differences were observed in background δ 13 C signatures of sediments, metazoans, and large, agglutinating protozoans, with values 2 to 3‰ lower at Site III than at Site I. Background δ 13 C signatures also varied as a function of taxon and of vertical position in the sediment column at Site III. The background δ 13 C value of carnivores was higher than that of surface-deposit feeders among Site I annelids, but no annelid feeding-group differences were observed at Site III. δ 13 C data from short-term (1 to 1.5 d) experiments revealed rapid diatom ingestion, primarily by agglutinated protozoans and annelids at Site I and mainly by annelids at Site III. Selective feeding on diatoms was exhibited by paraonid polychaetes, especially Aricidea spp. Exceptionally high uptake and retention of diatom C also was observed in the maldanid Praxillella sp., the nereid Ceratocephale sp. and several other surface-deposit feeding polychaetes. After 14 mo, little of the diatom 13 C remained at Site III, but high concentrations of the tracer were present in annelids and agglutinating protozoans at Site I. At both sites, non-annelid metazoans and subsurface-deposit feeding annelids exhibited the least uptake and retention of diatom C Our hypotheses that large-bodied taxa and shallow-dwelling infauna should have greatest access to freshly deposited organic matter were not borne out. Some small, deep-dwelling taxa acquired label more readily than large or near-surface forms. Differences in tracer fates between sites reflected greater vertical mixing at Site III. These results indicate heterogeneity in benthic processes along the Carolina margin, but suggest that labile organic matter is consumed quickly at both sites. Because most of the taxa found to consume freshly deposited diatoms in these experiments are typical of bathyal settings, we infer that phytodetritus reaching the seabed in margin environments is rapidly processed by protozoan and metazoan components of the benthic fauna.}, journal={MARINE ECOLOGY PROGRESS SERIES}, publisher={Inter-Research Science Center}, author={Levin, LA and Blair, NE and Martin, CM and DeMaster, DJ and Plaia, G and Thomas, CJ}, year={1999}, pages={37–54} }
 @article{blair_1998, title={The delta C-13 Of biogenic methane in marine sediments: the influence of C-org deposition rate}, volume={152}, ISSN={["0009-2541"]}, DOI={10.1016/S0009-2541(98)00102-8}, abstractNote={The δ13C of biogenic methane produced in marine sediments ranges from −110 to −55‰. The isotopic composition of the methane (δ13CCH4) is constrained by the fraction of metabolized organic carbon converted to CH4. The flux of labile organic carbon into the seabed (JMOC) and the availability of oxidants (Aox), such as O2 and SO4=, dictate that fraction, i.e., proportionately more methane should be produced as the ratio JMOC/Aox increases. Chemical, physical (e.g., sediment resuspension) and biological (bioturbation and bioirrigation) processes determine Aox. Given that δ13CCH4 is always less than δ13C of the metabolizable organic carbon, δ13CCH4 should increase when JMOC and the portion of metabolized carbon converted to methane increase. A positive linear correlation (r2=0.92) is observed between δ13CCH4 and JMOC for a database containing four continental margin sites. When the pore water sulfate gradient (ΔSO4=/Δdepth) is used as a surrogate for JMOC, the data set is extended to 15 locations spanning all latitudes. A linear relationship between the sulfate gradient and δ13CCH4 (r2=0.98) for shelf/slope environments suggests that either JMOC or JMOC/Aox is the master variable that controls the 13C/12C content of the biogenic methane. Carbonate precipitation and/or a methanogenic back reaction may obscure the correlation in deep-sea sediments. Evidence for the relationship between δ13CCH4 and JMOC appears to be preserved in Miocene-age dolomitic deposits.}, number={1-2}, journal={CHEMICAL GEOLOGY}, author={Blair, N}, year={1998}, month={Oct}, pages={139–150} }
 @article{levin_blair_demaster_plaia_fornes_martin_thomas_1997, title={Rapid subduction of organic matter by maldanid polychaetes on the North Carolina slope}, volume={55}, ISSN={["0022-2402"]}, DOI={10.1357/0022240973224337}, abstractNote={In situ tracer experiments conducted on the North Carolina continental slope reveal that tube-building worms (Polychaeta: Maldanidae) can, without ingestion, rapidly subduct freshly deposited, algal carbon ( 13 C-labeled diatoms) and inorganic materials (slope sediment and glass beads) to depths of 10 cm or more in the sediment column. Transport over 1.5 days appears to be nonselective but spatially patchy, creating localized, deep hotspots. As a result of this transport, relatively fresh organic matter becomes available soon after deposition to deep-dwelling microbes and other infauna, and both aerobic and anaerobic processes may be enhanced. Comparison of tracer subduction with estimates from a diffusive mixing model using 234 Th-based coefficients, suggests that maldanid subduction activities, within 1.5 d of particle deposition, could account for 25-100% of the mixing below 5 cm that occurs on 100-day time scales. Comparisons of community data from the North Carolina slope for different places and times indicate a correlation between the abundance of deep-dwelling maldanids and the abundance and the dwelling depth in the sediment column of other infauna. Pulsed inputs of organic matter occur frequently in margin environments and maldanid polychaetes are a common component of continental slope macrobenthos. Thus, the activities we observe are likely to be widespread and significant for chemical cycling (natural and anthropogenic materials) on the slope. We propose that species like maldanids, that rapidly redistribute labile organic matter within the seabed, probably function as keystone resource modifiers. They may exert a disproportionately strong influence (relative to their abundance) on the structure of infaunal communities and on the timing, location and nature of organic matter diagenesis and burial in continental margin sediments.}, number={3}, journal={JOURNAL OF MARINE RESEARCH}, publisher={Journal of Marine Research/Yale}, author={Levin, L and Blair, N and DeMaster, D and Plaia, G and Fornes, W and Martin, C and Thomas, C}, year={1997}, month={May}, pages={595–611} }