@article{nittrouer_demaster_kuehl_figueiredo_sternberg_faria_silveira_allison_kineke_ogston_et al._2021, title={Amazon Sediment Transport and Accumulation Along the Continuum of Mixed Fluvial and Marine Processes}, volume={13}, ISSN={["1941-1405"]}, DOI={10.1146/annurev-marine-010816-060457}, abstractNote={Sediment transfer from land to ocean begins in coastal settings and, for large rivers such as the Amazon, has dramatic impacts over thousands of kilometers covering diverse environmental conditions. In the relatively natural Amazon tidal river, combinations of fluvial and marine processes transition toward the ocean, affecting the transport and accumulation of sediment in floodplains and tributary mouths. The enormous discharge of Amazon fresh water causes estuarine processes to occur on the continental shelf, where much sediment accumulation creates a large clinoform structure and where additional sediment accumulates along its shoreward boundary in tidal flats and mangrove forests. Some remaining Amazon sediment is transported beyond the region near the river mouth, and fluvial forces on it diminish. Numerous perturbations to Amazon sediment transport and accumulation occur naturally, but human actions will likely dominate future change, and now is the time to document, understand, and mitigate their impacts. Expected final online publication date for the Annual Review of Marine Science, Volume 13 is January 3, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.}, journal={ANNUAL REVIEW OF MARINE SCIENCE, VOL 13, 2021}, author={Nittrouer, Charles A. and DeMaster, David J. and Kuehl, Steven A. and Figueiredo, Alberto G., Jr. and Sternberg, Richard W. and Faria, L. Ercilio C. and Silveira, Odete M. and Allison, Mead A. and Kineke, Gail C. and Ogston, Andrea S. and et al.}, year={2021}, pages={501–536} }
 @misc{ingels_aronson_smith_baco_bik_blake_brandt_cape_demaster_dolan_et al._2021, title={Antarctic ecosystem responses following ice-shelf collapse and iceberg calving: Science review and future research}, volume={12}, ISSN={["1757-7799"]}, DOI={10.1002/wcc.682}, abstractNote={The calving of A‐68, the 5,800‐km2, 1‐trillion‐ton iceberg shed from the Larsen C Ice Shelf in July 2017, is one of over 10 significant ice‐shelf loss events in the past few decades resulting from rapid warming around the Antarctic Peninsula. The rapid thinning, retreat, and collapse of ice shelves along the Antarctic Peninsula are harbingers of warming effects around the entire continent. Ice shelves cover more than 1.5 million km2 and fringe 75% of Antarctica's coastline, delineating the primary connections between the Antarctic continent, the continental ice, and the Southern Ocean. Changes in Antarctic ice shelves bring dramatic and large‐scale modifications to Southern Ocean ecosystems and continental ice movements, with global‐scale implications. The thinning and rate of future ice‐shelf demise is notoriously unpredictable, but models suggest increased shelf‐melt and calving will become more common. To date, little is known about sub‐ice‐shelf ecosystems, and our understanding of ecosystem change following collapse and calving is predominantly based on responsive science once collapses have occurred. In this review, we outline what is known about (a) ice‐shelf melt, volume loss, retreat, and calving, (b) ice‐shelf‐associated ecosystems through sub‐ice, sediment‐core, and pre‐collapse and post‐collapse studies, and (c) ecological responses in pelagic, sympagic, and benthic ecosystems. We then discuss major knowledge gaps and how science might address these gaps.}, number={1}, journal={WILEY INTERDISCIPLINARY REVIEWS-CLIMATE CHANGE}, author={Ingels, Jeroen and Aronson, Richard B. and Smith, Craig R. and Baco, Amy and Bik, Holly M. and Blake, James A. and Brandt, Angelika and Cape, Mattias and Demaster, David and Dolan, Emily and et al.}, year={2021}, month={Jan} }
 @article{isla_demaster_2021, title={Biogenic matter content in marine sediments in the vicinity of the Antarctic Peninsula: Recent sedimentary conditions under a diverse environment of production, transport, selective preservation and accumulation}, volume={304}, ISSN={["1872-9533"]}, DOI={10.1016/j.gca.2021.04.021}, abstractNote={Burial fluxes of organic carbon and biogenic silica were determined in 17 continental shelf sediment cores collected from the northern Weddell Sea, the Bransfield Strait, and the southern Drake Passage. Coring sites included open-shelf stations as well as slope and glacial trough environments, with water depths varying from 220 to 760 m. Apparent 210Pb accumulation rates from these cores ranged from 0.04 g m−2y−1 to 0.21 g m−2y−1 (1 to 3 mm y−1), with organic carbon burial rates ranging from 3 to 15 g OC m−2y−1 and biogenic silica accumulation rates ranging from 15 to 126 g SiO2 m−2y−1. OC contents below the surface mixed layer ranged from 0.26 to 1.51 wt. % (avg. 0.64 %). Biogenic silica contents at depth ranged from 2.3 to 11.2 wt. % (avg. 7.5%), with an average bSi/OC ratio (wt. %/wt. %) at depth of 12. Annual OC primary production rates and biogenic silica production rates in the euphotic zone were estimated from satellite chlorophyll-a data in the literature and from a seasonal model for biogenic particle export from surface waters. Based on these biogeochemical data, preservation efficiencies (i.e., mass burial rate/water column production rate) were calculated for organic carbon and biogenic silica. These preservation efficiency values ranged from 2 to 18% (avg. 9%) for OC and 8 to 106% (avg. 54%) for bSi. These relatively high preservation efficiencies resulted from extensive lateral sediment focusing (210Pb Psi (Ψ) values [burial flux/water column production rate] ranging from 2 to 33; avg. of 16), cold bottom water temperatures (2 to −2°C), and relatively high biogenic Si and OC production rates in the euphotic zone. The enhanced preservation efficiency for bSi relative to OC (i.e., 54% vs. 9%) in these Antarctic settings is consistent with the change in the phytoplankton bSi/OC (wt. %/wt. %) value of 2 for this area to the burial bSi/OC value of 12. Excess 210Pb activities in surface sediments varied from 4 to 47 dpm g−1. The surface mixed layer in the seabed varied in thickness from 0 to 4 cm. The penetration of excess 210Pb into these Antarctic Peninsula sediments varied from 6 to 28 cm (avg. 18 cm). The inventory of excess 210Pb in the seabed varied from 13 to 230 dpm cm−2 (avg. 110 dpm cm−2). Although 210Pb was the only radionuclide measured in this study, “apparent” 210Pb sediment accumulation rate (SAR) values from these 17 cores (assuming that deep bioturbation is negligible) are believed to be accurate SAR values because of good agreement between 210Pb and 14C chronologies from nearby cores reported in the literature.}, journal={GEOCHIMICA ET COSMOCHIMICA ACTA}, author={Isla, Enrique and DeMaster, David J.}, year={2021}, month={Jul}, pages={50–67} }
 @article{demaster_taylor_smith_isla_thomas_2021, title={Using Radiocarbon to Assess the Abundance, Distribution, and Nature of Labile Organic Carbon in Marine Sediments}, volume={35}, ISSN={["1944-9224"]}, DOI={10.1029/2020GB006676}, abstractNote={Positive 14C gradients have recently been observed within the surface mixed layer of several continental‐margin sediments. The best explanation for these positive 14C gradients is the occurrence and rapid degradation of labile organic carbon (LOC) in the upper 5–10 cm of the seabed. Based on a two‐component model for sedimentary organic matter (i.e., a planktonic labile component and an older refractory component), bulk 14Corg data were used to determine the abundances of LOC within the surface mixed layers of three cores from the West Antarctic Peninsula (WAP) shelf and one core from San Clemente Basin (California Borderland). LOC contents in surface samples from the four stations varied from 0.5 to 1.1 mg/cm3, comprising 20% (San Clemente Basin) to 80% (WAP, Sta. G) of the total organic carbon. By incorporating a steady state diagenetic model and particle‐mixing bioturbation coefficients, the LOC profiles were used to determine LOC turnover times (LOC τ) and LOC e‐folding depths. The LOC τ values for the West Antarctic Peninsula sediments varied from 0.09 to 0.59 years, whereas the LOC τ value from the San Clemente Basin core was 63 years. The LOC e‐folding depths for the WAP stations varied from 0.8 to 3.4 cm, in contrast to the LOC e‐folding depth in San Clemente Basin, which was 4.0 cm. LOC characteristics from the four cores examined in this study were compared to LOC data in the literature as a means of substantiating the overall 14Corg‐based approach and justifying model assumptions.}, number={6}, journal={GLOBAL BIOGEOCHEMICAL CYCLES}, author={DeMaster, D. J. and Taylor, R. S. and Smith, C. R. and Isla, E. and Thomas, C. J.}, year={2021}, month={Jun} }
 @article{taylor_demaster_burdige_2020, title={Assessing the distribution of labile organic carbon from diverse depositional environments on the West Antarctic Peninsula shelf}, volume={156}, ISSN={["1879-0119"]}, DOI={10.1016/j.dsr.2019.103166}, abstractNote={The seabed distributions of labile organic carbon (LOC), i.e., recently produced organic matter from marine plankton, were studied in a variety of depositional environments on the West Antarctic Peninsula continental shelf using the naturally occurring radioisotopes, 14C, 210Pb and 234Th. The effects of bioturbation on the LOC pool were assessed on short-term (seasonal, using 234Thxs within the upper, 2–5 cm) and long-term (decadal, using 210Pbxs from 3-22 cm) timescales to generate LOC degradation coefficients (k) and mean residence times (MRT or τ-LOC) as a function of depth within the sediment column. Based on 234Th distributions, mixing coefficients (Db) ranged from 2 cm2/y to 36 cm2/y, which resulted in LOC MRT values that varied from 0.8y to 9.8y. Based on 210Pb distributions, Db values at depth ranged from 0.2 cm2/y to 1.8 cm2/y, resulting in MRT values that varied from 32y to 4900y. Along the West Antarctic Peninsula, seabed inventories of LOC varied between 17-70 mg/cm2. Bulk LOC becomes less reactive and ages with time during resuspension and transport across the shelf and as LOC is transported deeper within the sediment column by infaunal feeding activities.}, journal={DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS}, author={Taylor, Richard S. and DeMaster, David J. and Burdige, David J.}, year={2020}, month={Feb} }
 @article{taylor_demaster_smith_thomas_2020, title={Evaluating the effects of regional climate trends along the West Antarctic Peninsula shelf based on the seabed distribution of naturally occurring radioisotopic tracers}, volume={429}, ISSN={["1872-6151"]}, DOI={10.1016/j.margeo.2020.106315}, abstractNote={Measurements of 230Th, 14C, 210Pb and 234Th activities were made on sediment cores collected along a N-S transect exhibiting a gradient in annual sea-ice duration off the West Antarctic Peninsula. The resultant data were used to evaluate the effects of regional warming on particle flux reaching the seabed on timescales from millennial to seasonal. Shelf samples were collected at five stations, over three cruises, between February 2008 and March 2009, as part of the FOODBANCS2 Project. Sea-ice conditions (the number of days ice-free prior to core collection) were evaluated at the five stations to understand the relationship between ice abundance and particle/radionuclide flux. Based on the millennial tracer 14C, rates of sediment accumulation along the peninsula decrease southward, consistent with the observed sea-ice gradient. 230Th data provide additional evidence on millennial timescales that sediment focusing (i.e., lateral transport) occurs to a greater extent in the northern reaches of the study area compared to the southernmost stations. The distribution of steady-state, 210Pb flux to the seabed (representing centurial trends) displays a similar trend to 14C, showing higher radionuclide/particle flux in the northern study area (where sea-ice duration is diminished) and lower flux southward as sea-ice duration increases. Additionally, 210Pb data suggest that lateral transport plays an important role in the sediment distributions of this radiotracer on hundred-year timescales, which is explainable by the relatively short circulation times of peninsular waters relative to 210Pb's half-life. On seasonal and annual time scales, the distribution of steady-state 234Th flux to the seabed shows an increase in radionuclide flux at the southernmost stations. This increase in radionuclide flux on seasonal and annual time scales is consistent with the warming trend along the peninsula and the reduction in sea-ice duration over the past decade. A significant statistical relationship, however, could not be established between annual sea-ice free days and 234Th-derived particle flux to the seabed. The fluxes/distributions of long-lived particle-reactive tracers (14C, 230Th, and 210Pb) on the West Antarctic Peninsula shelf appear to be controlled primarily by the long-term pattern of increasing annual sea-ice duration in the southward direction, whereas the fluxes of the short-lived tracer (234Th) are consistent with the more recent decreases in sea-ice duration (associated with climate change) that have occurred over the past decade, primarily in the southern West Antarctic Peninsula stations.}, journal={MARINE GEOLOGY}, author={Taylor, Richard S. and DeMaster, David J. and Smith, Craig R. and Thomas, Carrie J.}, year={2020}, month={Nov} }
 @article{demaster_2019, title={The Global Marine Silica Budget: Sources and Sinks}, DOI={10.1016/B978-0-12-409548-9.10799-7}, abstractNote={This article presents a review of the sources of dissolved silicate to the marine environment and the associated sinks (i.e., burial sites) of particulate silica (SiO2) in the oceans. The dominant sources of dissolved silicate to the oceans are from rivers, groundwater, rainfall, and hydrothermal vent flux, whereas the dominant removal mechanisms for silica are the burial of marine diatoms in nearshore, continental margin, and deep-sea sediments. Burial of silica as sponge spicules and authigenic clay minerals certainly occurs, but they are expected to make a small contribution to the overall marine silica budget.}, journal={ENCYCLOPEDIA OF OCEAN SCIENCES, VOL 1: MARINE BIOGEOCHEMISTRY, 3RD EDITION}, author={DeMaster, David J.}, year={2019}, pages={473–483} }
 @misc{gutt_isla_bertler_bodeker_bracegirdle_cavanagh_comiso_convey_cummings_de conto_et al._2018, title={Cross-disciplinarity in the advance of Antarctic ecosystem research}, volume={37}, ISSN={["1876-7478"]}, DOI={10.1016/j.margen.2017.09.006}, abstractNote={The biodiversity, ecosystem services and climate variability of the Antarctic continent and the Southern Ocean are major components of the whole Earth system. Antarctic ecosystems are driven more strongly by the physical environment than many other marine and terrestrial ecosystems. As a consequence, to understand ecological functioning, cross-disciplinary studies are especially important in Antarctic research. The conceptual study presented here is based on a workshop initiated by the Research Programme Antarctic Thresholds – Ecosystem Resilience and Adaptation of the Scientific Committee on Antarctic Research, which focussed on challenges in identifying and applying cross-disciplinary approaches in the Antarctic. Novel ideas and first steps in their implementation were clustered into eight themes. These ranged from scale problems, through risk maps, and organism/ecosystem responses to multiple environmental changes and evolutionary processes. Scaling models and data across different spatial and temporal scales were identified as an overarching challenge. Approaches to bridge gaps in Antarctic research programmes included multi-disciplinary monitoring, linking biomolecular findings and simulated physical environments, as well as integrative ecological modelling. The results of advanced cross-disciplinary approaches can contribute significantly to our knowledge of Antarctic and global ecosystem functioning, the consequences of climate change, and to global assessments that ultimately benefit humankind.}, journal={MARINE GENOMICS}, author={Gutt, J. and Isla, E. and Bertler, A. N. and Bodeker, G. E. and Bracegirdle, T. J. and Cavanagh, R. D. and Comiso, J. C. and Convey, P. and Cummings, V. and De Conto, R. and et al.}, year={2018}, month={Feb}, pages={1–17} }
 @article{isla_demaster_2018, title={Labile organic carbon dynamics in continental shelf sediments after the recent collapse of the Larsen ice shelves off the eastern Antarctic Peninsula: A radiochemical approach}, volume={242}, ISSN={["1872-9533"]}, DOI={10.1016/j.gca.2018.08.011}, abstractNote={Labile organic carbon (LOC) dynamics (i.e., of recently produced, planktonic material) and sediment dynamics were studied in the seabed using naturally occurring 14Corg and 210Pb measurements in the region where the Larsen Ice Shelves A and B were floating almost two decades ago. A non-steady-state diagenetic model was used to estimate sediment mixing coefficients as well as LOC fluxes to the seabed and LOC turnover times (i.e., mean residence times) in a suite of 14 sediment cores from the continental shelf, including a glacial trough. At four of the stations, cores were collected during 2007 and 2011 cruises, enabling a time-series approach for understanding the evolution of sedimentary processes and LOC dynamics in the deposits below a collapsed ice shelf. Sediment mixing coefficients, based on non-steady-state 210Pb profiles, varied between 0.01 cm2 y−1 and 1.6 cm2 y−1 in these post-ice shelf sediments. These values were similar to those found in polar deep-sea environments, where sedimentary conditions are less dynamic than in shallower provinces. LOC, whose abundance decreased uniformly with depth, was detected to depths ranging from 2 to 16 cm, with LOC seabed inventories varying from 1.5 to 22 mg LOC cm−2. Excess 210Pb and LOC fluxes were relatively uniform across the study area suggesting that similar particle fluxes have taken place within the Larsen system since the disintegration of the various ice shelves. The LOC mean residence time at the different stations varied from 3 y to >60 y. The 14Corg approach, calculating LOC content based on a two-end member model with planktonic 14Corg as the labile carbon end member, most closely correlated with the lipid content of the sediment, which has been considered one of the best descriptors of reactive organic matter readily available to benthic consumers. We suggest that the irregular combination of sea ice coverage, organic matter production and supply to the sea floor introduce scatter in the determination of sediment and LOC dynamics such that short-term temporal (<5 years) and spatial trends could not be readily resolved.}, journal={GEOCHIMICA ET COSMOCHIMICA ACTA}, author={Isla, E. and DeMaster, D. J.}, year={2018}, month={Dec}, pages={34–50} }
 @article{liu_demaster_nittrouer_eidam_nguyen_2017, title={A seismic study of the Mekong subaqueous delta: Proximal versus distal sediment accumulation}, volume={147}, ISSN={0278-4343}, url={http://dx.doi.org/10.1016/J.CSR.2017.07.009}, DOI={10.1016/j.csr.2017.07.009}, abstractNote={The Mekong River Delta is one of the largest in Asia. To understand its sediment distribution, thickness, mass budget, stratigraphic sequences and sediment-transport process, extensive geophysical and geochemical surveys were conducted on the inner portions of the adjacent continental shelf. Analyses of > 80 high-resolution Chirp-sonar profiles show the Mekong River has formed a classic sigmoidal cross-shelf clinoform in the proximal areas, up to 15 m thick, with topset, foreset and bottomset facies, but constrained to water depths of < 20 m. Beyond this depth, the East Sea/western South China Sea shelf is dominated by relict silt, sand and gravel with patches of early to middle Holocene mud deposits. Parallel to shore, the Mekong-derived sediment has extended > 250 > 300 km southwestward to the tip of the Ca Mau Peninsula, forming a distal mud depocenter up to 22 m thick, and extending into the Gulf of Thailand. A large erosional trough or channel (up to 8 m deeper than the surrounding seafloor and parallel to the shore) was found on the top of the clinoform, east of the Ca Mau Peninsula. Based on the thicknesses and distribution revealed by Chirp sonar profiles, the total estimated volume of the Mekong River subaqueous clinoform on the shelf is ~120 km3, which is equivalent to ~120–140 × 109 t of sediment using an average sediment dry-bulk density of 1.0–1.2 g/cm3. Assuming the subaqueous deltaic deposit has formed within ~1000 yr, the calculated millennial-timescale average sediment discharge to the shelf could be 120–140 × 106 t per year. Spatially, the proximal subaqueous delta has accumulated ~45 × 109 t (~33%) of sediment; the distal part around the Ca Mau Peninsula has received ~55 × 109 t (~42%) of sediment; and the remaining ~35 × 109 t (~25%) has accumulated within the central transition area, although the coastline and shoreface in this area are presently eroding. The spatially averaged 1000-yr-scale accumulate rate is up to 2 cm/yr. Compared to other tide-dominated fluvial dispersal systems, the Mekong River system has a relatively young (≤1000 yr) subaqueous delta, a shallow rollover at 4–6 m water depth, gentle foreset gradients (0.03–0.57°), and a short cross-shelf dimension of 15–20 km within 20-m water depth. Like the Amazon, Po, and Yangtze rivers, the Mekong River has developed a pervasive along-shelf deposit, which in this case extends > 250 > 300km to the southwest as a result of the superimposed tidal processes, wave-induced resuspension, and a strong low-flow season coastal current.}, journal={Continental Shelf Research}, publisher={Elsevier BV}, author={Liu, J. Paul and DeMaster, David J. and Nittrouer, Charles A. and Eidam, Emily F. and Nguyen, Thanh T.}, year={2017}, month={Sep}, pages={197–212} }
 @article{demaster_liu_eidam_nittrouer_nguyen_2017, title={Determining rates of sediment accumulation on the Mekong shelf: Timescales, steady-state assumptions, and radiochemical tracers}, volume={147}, ISSN={0278-4343}, url={http://dx.doi.org/10.1016/J.CSR.2017.06.011}, DOI={10.1016/j.csr.2017.06.011}, abstractNote={Thirty-two kasten cores, collected from the proximal Mekong continental shelf, have been analyzed for their excess 210Pb distributions in an effort to establish rates of sediment accumulation over the past 100 years. The length of the cores varied from 0.5 to 3 m, and stations sampled topset, foreset, and bottomset beds (water depths 7–21 m). Apparent excess 210Pb sediment accumulation rates ranged from > 10 cm/y (no down-core decrease of excess activity over 300 cm core length) near the Song Hau river mouth, to 1–3 cm/y in topset and foreset beds within 20–50 km of the river mouth, to rates as low as 0.4 cm/y in cores from bottomset beds. The 210Pb sediment accumulation rates yield an overall sediment burial rate of 6.1 × 1013 g/y for the proximal deltaic deposits, which corresponds to 43% of the total modern Mekong sediment burial on the southern Vietnam shelf (1.4 × 1014 g/y; based on our 210Pb and seismic data and 210Pb data from the literature). This shelf burial rate is in reasonable agreement with current long-term estimates of Mekong River sediment discharge (1.3–1.6 × 1014 g/y) from the literature. The inventory of excess 210Pb in the proximal Mekong deltaic deposits indicates that the shoreward flow of offshore water (entrained during river/ocean mixing) is approximately twice the flow of the Mekong freshwater discharge. Organic-carbon 14C ages were measured on 10 cores from the proximal Mekong delta and compared to 210Pb sediment accumulation rates in the same core. The 210Pb accumulation rates in all 10 cores were considered to be more robust and accurate than the 14C geochronologies, primarily because of down-core variations in the source of organic carbon deposited on the seafloor (old terrestrial carbon versus younger marine carbon). Variations in the source of organic carbon accumulating in the seabed were resolved by measuring the δ13C value of the seabed organic carbon.}, journal={Continental Shelf Research}, publisher={Elsevier BV}, author={DeMaster, D.J. and Liu, J.P. and Eidam, E. and Nittrouer, C.A. and Nguyen, T.T.}, year={2017}, month={Sep}, pages={182–196} }
 @article{eidam_nittrouer_ogston_demaster_liu_nguyen_nguyen_2017, title={Dynamic controls on shallow clinoform geometry: Mekong Delta, Vietnam}, volume={147}, ISSN={0278-4343}, url={http://dx.doi.org/10.1016/J.CSR.2017.06.001}, DOI={10.1016/j.csr.2017.06.001}, abstractNote={Compound deltas, composed of a subaerial delta plain and subaqueous clinoform, are common termini of large rivers. The transition between clinoform topset and foreset, or subaqueous rollover point, is located at 25–40-m water depth for many large tide-dominated deltas; this depth is controlled by removal of sediment from the topset by waves, currents, and gravity flows. However, the Mekong Delta, which has been classified as a mixed-energy system, has a relatively shallow subaqueous rollover at 4–6-m depth. This study evaluates dynamical measurements and seabed cores collected in Sep 2014 and Mar 2015 to understand processes of sediment transfer across the subaqueous delta, and evaluate possible linkages to geometry. During the southwest rainy monsoon (Sep 2014), high river discharge, landward return flow under the river plume, and regional circulation patterns facilitated limited sediment flux to the topset and foreset, and promoted alongshore flux to the northeast. Net observed sediment fluxes in Sep 2014 were landward, however, consistent with hypotheses about seasonal storage on the topset. During the northeast rainy monsoon, low river discharge and wind-driven currents facilitated intense landward and southwestward fluxes of sediment. In both seasons, bed shear velocities frequently exceeded the 0.01–0.02 m/s threshold of motion for sand, even in the absence of strong wave energy. Most sediment transport occurred at water depths <14 m, as expected from observed cross-shelf gradients of sedimentation. Sediment accumulation rates were highest on the upper and lower foreset beds (>4 cm/yr at <10 m depth, and 3–8 cm/yr at ~10–20 m depth) and lowest on the bottomset beds. Physically laminated sediments transitioned into mottled sediments between the upper foreset and bottomset regions. Application of a simple wave-stress model to the Mekong and several other clinoforms illustrates that shallow systems are not necessarily energy-limited, and thus rollover depths cannot be predicted solely by bed-stress distributions. In systems like the subaqueous Mekong Delta, direction of transport may have a key impact on morphology.}, journal={Continental Shelf Research}, publisher={Elsevier BV}, author={Eidam, E.F. and Nittrouer, C.A. and Ogston, A.S. and DeMaster, D.J. and Liu, J.P. and Nguyen, T.T. and Nguyen, T.N.}, year={2017}, month={Sep}, pages={165–181} }
 @article{liu_demaster_nguyen_saito_nguyen_ta_li_2017, title={Stratigraphic Formation of the Mekong River Delta and Its Recent Shoreline Changes}, volume={30}, ISSN={["1042-8275"]}, DOI={10.5670/oceanog.2017.316}, abstractNote={USAGE Permission is granted to copy this article for use in teaching and research. Republication, systematic reproduction, or collective redistribution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The Oceanography Society. Send all correspondence to: info@tos.org or The Oceanography Society, PO Box 1931, Rockville, MD 20849-1931, USA. Oceanography THE OFFICIAL MAGAZINE OF THE OCEANOGRAPHY SOCIETY}, number={3}, journal={OCEANOGRAPHY}, author={Liu, J. Paul and DeMaster, David J. and Nguyen, Thanh T. and Saito, Yoshiki and Nguyen, Van Lap and Ta, Thi Kim Oanh and Li, Xing}, year={2017}, month={Sep}, pages={72–83} }
 @article{nittrouer_demaster_eidam_nguyen_liu_ogston_phung_2017, title={The Mekong continental shelf: Primary sink for deltaic sediment particles and their passengers}, volume={30}, number={3}, journal={Oceanography}, author={Nittrouer, C. A. and DeMaster, D. J. and Eidam, E. F. and Nguyen, T. T. and Liu, J. P. and Ogston, A. S. and Phung, P. V.}, year={2017}, pages={60–70} }
 @article{xue_liu_demaster_leithold_wan_ge_nguyen_ta_2014, title={Sedimentary processes on the Mekong subaqueous delta: Clay mineral and geochemical analysis}, volume={79}, ISSN={1367-9120}, url={http://dx.doi.org/10.1016/j.jseaes.2012.07.012}, DOI={10.1016/j.jseaes.2012.07.012}, abstractNote={Sedimentary processes on the inner Mekong Shelf were investigated by examining the characteristics of sediments sampled in gravity cores at 15 locations, including grain size, clay mineralogy, sediment accumulation rates, and the elemental and stable carbon isotopic composition of organic matter (atomic C/N ratios and δ13C). Deltaic deposits exhibit contrasting characteristics along different sides of the delta plain (South China Sea, SCS hereafter, to the east and Gulf of Thailand, GOT hereafter, to the west) as well as on and off the subaqueous deltaic system. On one hand, cores recovered from the subaqueous delta in the SCS/GOT are consisted of poorly/well sorted sediments with similar/different clay mineral assemblage with/from Mekong sediments. Excess 210Pb profiles, supported by 14C chronologies, indicate either “non-steady” (SCS side) or “rapid accumulation” (GOT side) processes on the subaqueous delta. The δ13C and C/N ratio indicate a mixture of terrestrial and marine-sourced organic matter in the deltaic sediment. On the other hand, cores recovered from areas with no deltaic deposits or seaward of the subaqueous delta show excess 210Pb profiles indicating “steady-state” accumulation with a greater proportion of marine-sourced organic matter. Core analysis’s relevance with local depositional environment and previous acoustic profiling are discussed.}, journal={Journal of Asian Earth Sciences}, publisher={Elsevier BV}, author={Xue, Zuo and Liu, J. Paul and DeMaster, Dave and Leithold, Elana L. and Wan, Shiming and Ge, Qian and Nguyen, Van Lap and Ta, Thi Kim Oanh}, year={2014}, month={Jan}, pages={520–528} }
 @article{sane_isla_angeles barcena_demaster_2013, title={A Shift in the Biogenic Silica of Sediment in the Larsen B Continental Shelf, Off the Eastern Antarctic Peninsula, Resulting from Climate Change}, volume={8}, ISSN={["1932-6203"]}, DOI={10.1371/journal.pone.0052632}, abstractNote={In 2002, section B of the Larsen ice shelf, off of the Eastern Antarctic Peninsula, collapsed and created the opportunity to study whether the changes at the sea surface left evidence in the sedimentary record. Biogenic silica is major constituent of Antarctic marine sediment, and its presence in the sediment column is associated with diatom production in the euphotic zone. The abundance of diatom valves and the number of sponge spicules in the biogenic silica was analyzed to determine how the origin of the biogenic silica in the upper layers of the sediment column responded to recent environmental changes. Diatom valves were present only in the upper 2 cm of sediment, which roughly corresponds to the period after the collapse of the ice shelf. In contrast, sponge spicules, a more robust form of biogenic silica, were also found below the upper 2 cm layer of the sediment column. Our results indicate that in this region most of the biogenic silica in the sedimentary record originated from sponge spicules rather than diatoms during the time when the sea surface was covered by the Larsen ice shelf. Since the collapse of the ice shelf, the development of phytoplankton blooms and the consequent influx of diatom debris to the seabed have shifted the biogenic silica record to one dominated by diatom debris, as occurs in most of the Antarctic marine sediment. This shift provides further evidence of the anthropogenic changes to the benthic habitats of the Antarctic and will improve the interpretation of the sedimentary record in Polar Regions where these events occur.}, number={1}, journal={PLOS ONE}, author={Sane, Elisabet and Isla, Enrique and Angeles Barcena, Maria and DeMaster, David J.}, year={2013}, month={Jan} }
 @article{zhang_dickhut_demaster_pohl_lohmann_2013, title={Organochlorine Pollutants in Western Antarctic Peninsula Sediments and Benthic Deposit Feeders}, volume={47}, ISSN={["1520-5851"]}, DOI={10.1021/es303553h}, abstractNote={Sediments and benthic deposit feeding holothurians were collected near the Palmer Long Term Ecological Research grid during the austral winter of 2008. Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were measured in Western Antarctic Peninsula continental shelf sediments, porewater, and benthic biota. Concentrations and fluxes in sediments decreased sharply away from the tip of the peninsula toward its interior. Sedimentary PCB fluxes were an order of magnitude lower than reported elsewhere, supporting the notion of a pristiner Antarctic environment. Hexa-chlorinated biphenyls dominated (40-100%) the PCB profiles in the sediments, while trichlorinated biphenyl 28 was the most abundant PCB congener in the porewater. PCB and OCP concentrations in holothurians were comparable to concentrations in other low trophic level biota in the Antarctic food web (i.e., krill). The partitioning of PCBs and OCPs between the sediments and porewater can be explained by a dual-mode model, which included both organic carbon and black carbon as partitioning media. Alternatively, a simpler one-parameter prediction assuming coal tar-like organic carbon performed equally well in explaining porewater concentrations The majorities of PCBs (63-94%) in the Western Antarctic Peninsula sediments were bound to black carbon or recalcitrant tar-like organic carbon, thereby lowering porewater concentrations. PCBs and OCPs in the holothurians were in equilibrium with those in the porewater.}, number={11}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Zhang, Lin and Dickhut, Rebecca and DeMaster, Dave and Pohl, Kari and Lohmann, Rainer}, year={2013}, month={Jun}, pages={5643–5651} }
 @article{smith_demaster_thomas_srsen_grange_evrard_deleo_2012, title={PELAGIC-BENTHIC COUPLING, FOOD BANKS, AND CLIMATE CHANGE ON THE WEST ANTARCTIC PENINSULA SHELF}, volume={25}, ISSN={["1042-8275"]}, DOI={10.5670/oceanog.2012.94}, abstractNote={The West Antarctic Peninsula (WAP) shelf is deep and detritus-based (i.e., it is fueled by organic material sinking from intense seasonal cycles of primary production in the water column), leading to pelagic-benthic coupling. The WAP is warming rapidly, yielding increases in seawater temperatures and reductions in sea ice that may fundamentally alter pelagic-benthic coupling and shelf benthic ecosystems. RVIB Nathaniel B. Palmer and ARSV Laurence M. Gould have provided year-round access to the WAP sea ice zone, facilitating studies of pelagic-benthic coupling and climate change. In the Food for Benthos along the Antarctic Continental Shelf (FOODBANCS) Project, we conducted a 15-month field program to evaluate benthic ecosystem function across the mid-WAP shelf, testing the hypothesis that "phytodetrital material deposited from the summer bloom provides a sustained source of food for benthic detritivores during winter months, when organic-matter flux from the water column is extremely low." We found that the intense seasonality in primary production and food availability in the WAP water column is heavily dampened at the shelf floor by the presence of a "food bank" that sustains benthic ecosystem functions (including sediment-community respiration, deposit feeding, vitellogenesis, spawning, and recruitment of benthos) over the winter; this food bank also influences community structure and life-history strategies of the WAP benthos. The persistence of the food bank may be mediated by low bottom-water temperatures, with the consequence that climate warming might reduce food availability in shelf communities. During the FOODBANCS2 Project, we studied the benthic ecosystem response to the strong latitudinal sea ice gradient along the WAP to explore the ecosystem consequences of sea ice loss from climate change. We found that some aspects of benthic ecosystem structure (e.g., macrofaunal dominance by the polychaete Aurospio foodbancsia) covaried with sea ice duration and are likely to be sensitive to sea ice loss. Other benthic parameters (e.g., the standing crop of macro- and megabenthos) exhibited nonlinear responses, with evidence of resilience along much of the sea ice gradient and abrupt change near one end. Still other benthic parameters (e.g., sediment community respiration) changed very little with sea ice duration. We also found that climate warming is facilitating invasion of the WAP shelf by predacious king crabs, with dramatic reduction in benthic biodiversity and altered ecosystem function. In summary, some important benthic ecosystem parameters along the WAP may be resilient to climate-induced changes in pelagic-benthic coupling, while many others may be highly sensitive, responding nonlinearly to sea ice loss. Incorporation of climate change effects into WAP benthic ecosystem models, including the effects of invasive species, will be challenging until mechanisms, nonlinearities, synergies, and tipping points of climate change effects are better understood. - See more at: http://www.tos.org/oceanography/archive/25-3_smith_c.html#sthash.YDijuDU5.dpuf}, number={3}, journal={OCEANOGRAPHY}, author={Smith, Craig R. and DeMaster, David J. and Thomas, Carrie and Srsen, Pavica and Grange, Laura and Evrard, Victor and DeLeo, Fabio}, year={2012}, month={Sep}, pages={188–201} }
 @article{sane_isla_pruski_barcena_vetion_demaster_2011, title={Diatom valve distribution and sedimentary fatty acid composition in Larsen Bay, Eastern Antarctica Peninsula}, volume={31}, ISSN={["1873-6955"]}, DOI={10.1016/j.csr.2011.04.002}, abstractNote={During austral summer 2006–2007, five sediment cores were recovered from the Eastern Antarctic Peninsula (EAP) continental shelf. Microscopic observations and sediment fatty acid (FA) composition analyses were carried out to investigate whether the drastic changes at the sea surface in EAP may be reflected in the sedimentary record. A sharp decrease in the number of diatom valves was observed below 2 cm depth. This difference between the upper 2 cm of sediment and the deeper part of the sediment column was attributed to the drastic change in the upper water column conditions after the collapse of the ice shelves, which allowed the arrival of phytoplankton debris and fresh organic matter to the sea floor in EAP. The presence of bacterial-, zooplankton- and detrital-related FA throughout EAP cores suggests that there has been an input of older and more refractory organic matter into the region, presumably by lateral transport before the Larsen ice shelves disintegration.}, number={11}, journal={CONTINENTAL SHELF RESEARCH}, author={Sane, E. and Isla, E. and Pruski, A. M. and Barcena, M. A. and Vetion, G. and DeMaster, D.}, year={2011}, month={Aug}, pages={1161–1168} }
 @article{sane_isla_gremare_gutt_vetion_demaster_2011, title={Pigments in sediments beneath recently collapsed ice shelves: The case of Larsen A and B shelves, Antarctic Peninsula}, volume={65}, ISSN={["1873-1414"]}, DOI={10.1016/j.seares.2010.07.005}, abstractNote={In March 2002, 3200 km2 of the Larsen B ice shelf collapsed off the Eastern Antarctic Peninsula (EAP). In the austral summer of 2006, sea floor sediment was recovered beneath the extinct Larsen B ice shelf and in a region off the Northern Antarctic Peninsula (NAP), which has been free of ice shelves for more than 1000 yr. To assess changes in the chemical composition of the sediment after ice shelf collapses, chlorophylls and pheophytins were measured in sediment cores at six stations. This is the first time that chlorophyll pigments have been analysed in sediment samples from regions under recently collapsed ice shelves. Five years after the ice shelf collapse, Chla and Chlc concentrations were similar in the interfacial sediment (upper 1 cm) of NAP and EAP regions. However, in EAP Chla and Chlc concentrations decreased more rapidly with depth in the sediment column and were negligible below 2 cm depth. The high Chla to Pheoa ratios indicated that sedimentary pigments found in EAP had undergone limited degradation suggesting that they were locally produced rather than laterally advected. Complementary information from excess 210Pb activity and diatom valve distributions provided further evidence that the pigment fluxes to the seabed in EAP took place only after the ice shelf collapse.}, number={1}, journal={JOURNAL OF SEA RESEARCH}, author={Sane, E. and Isla, E. and Gremare, A. and Gutt, J. and Vetion, G. and DeMaster, D. J.}, year={2011}, month={Jan}, pages={94–102} }
 @article{null_corbett_demaster_burkholder_thomas_reed_2011, title={Porewater advection of ammonium into the Neuse River Estuary, North Carolina, USA}, volume={95}, ISSN={["1096-0015"]}, DOI={10.1016/j.ecss.2011.09.016}, abstractNote={Radon-222 (222Rn) and ammonium (NH4+) were measured in interstitial water of the Neuse River Estuary (NRE), North Carolina, USA to determine the advective flux of NH4+ from sediments to the overlying water column. Porewater samples were collected over an annual cycle from multi-level piezometers installed in nearshore sites. NH4+ concentrations in sandy environments of the NRE were 10-fold higher than concentrations in the overlying water column. Shallow porewaters exhibited seasonal variations in NH4+ concentrations, which resulted in temporal changes in NH4+ flux from the sediment. Submarine groundwater discharge (SGD) was measured indirectly by using 222Rn as a tracer and directly via seepage meters. Discharge rates were variable depending upon the sampling location and season. The mean SGD was 9.1 ± 1.5 cm d−1 with a maximum SGD during spring at a rate of 13.6 cm d−1 based on 222Rn porewater distribution. High porewater NH4+ concentrations in sandy nearshore sediments contributed NH4+ to the overlying water via groundwater discharge as an advective process. The overall mean NH4+ flux was 11.2 ± 2.0 mmol NH4+ m−2 d−1. Seasonal trends in groundwater seepage rates and NH4+ concentration suggest that groundwater is an important mechanism advecting nutrients from porewaters to surface waters, which is comparable to riverine NH4+ discharge. SGD N:P ratios (NH4+ as N) were >16:1, indicating that SGD is an important contributor of inorganic N for phytoplankton growth and may influence the NRE toward a less N-limited system. The data from this study will advance current understanding about the role of NH4+ in the progressive eutrophication of shallow estuarine ecosystems.}, number={2-3}, journal={ESTUARINE COASTAL AND SHELF SCIENCE}, author={Null, Kimberly A. and Corbett, D. Reide and DeMaster, David J. and Burkholder, JoAnn M. and Thomas, Carrie J. and Reed, Robert E.}, year={2011}, month={Dec}, pages={314–325} }
 @article{xue_liu_demaster_van nguyen_ta_2010, title={Late Holocene Evolution of the Mekong Subaqueous Delta, Southern Vietnam}, volume={269}, ISSN={0025-3227}, url={http://dx.doi.org/10.1016/j.margeo.2009.12.005}, DOI={10.1016/j.margeo.2009.12.005}, abstractNote={As Asia's third largest river, with regard to sediment load, the Mekong River delivers approximately 160 million tons of sediment per year to the South China Sea. High-resolution seismic profiling and coring during 2006 and 2007 cruises revealed a low gradient, subaqueous delta system, up to 20 m thick, surrounding the modern Mekong River Delta (MRD) in the west of the South China Sea. Based on clinoform structure, grain size, 210Pb, AMS 14C, and δ13C results, the subaqueous delta is divided into four zones defined by different sedimentary processes and depositional features. Over the past 3000 yr, the evolution of the MRD has shown a morphological asymmetry indicated by a large down-drift area and a rapid progradation around Cape Camau, ∼ 200 km downstream from the river mouth. This asymmetric feature is consistent with increased wave influence. The strong southwestward coastal current, strengthened by the strong NE monsoon, plays an important role locally in longshore transport of resuspended sediments into the Gulf of Thailand. A late Holocene sediment budget for the MRD has been determined, based on the area and thickness of deltaic sediment. Approximately 80% of Mekong delivered sediment has been trapped within the delta area, which, together with a falling sea-level, resulted in a rapidly prograding MRD over the past 3000 yr.}, number={1-2}, journal={Marine Geology}, publisher={Elsevier BV}, author={Xue, Zuo and Liu, J. Paul and DeMaster, Dave and Van Nguyen, Lap and Ta, Thi Kim Oanh}, year={2010}, month={Feb}, pages={46–60} }
 @article{hartnett_boehme_thomas_demaster_smith_2008, title={Benthic oxygen fluxes and denitrification rates from high-resolution porewater profiles from the Western Antarctic Peninsula continental shelf}, volume={55}, ISSN={["1879-0100"]}, DOI={10.1016/j.dsr2.2008.06.002}, abstractNote={Benthic fluxes of dissolved oxygen and nitrate were calculated from high-resolution porewater profiles collected on the continental margin of the Western Antarctic Peninsula. Profiles were collected in four seasons between March 2000 and February 2001 as part of the FOODBANCS program. Oxygen consumption rates ranged from 0.92 to 3.11 mmol O2 m−2 d−1 over the course of the year with an average annual oxygen consumption rate of 1.74 mmol O2 m−2 d−1. The oxygen fluxes follow a trend similar to the particulate carbon export flux with smaller fluxes during the winter and larger fluxes during the spring bloom period. However, the range in oxygen fluxes is substantially smaller than the range in the particulate carbon export. Denitrification rates ranged from 0.66 to 1.46 mmol N m−2 d−1, and the average annual denitrification rate was 1.29 mmol N m−2 d−1. The O2 consumption and denitrification rates are of similar magnitude to rates measured on other deep (∼500 m) continental margins. Denitrification rates are strongly coupled to nitrification rates, with coupled nitrification–denitrification accounting for more than 80% of the total denitrification rate in these sediments. The Antarctic continental-margin sediment denitrification rates correspond to ∼3–5 Tg N yr−1, and thus these continental-margin sediments account for roughly 1–2% of the global sediment denitrification signal.}, number={22-23}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Hartnett, Hilairy and Boehme, Susan and Thomas, Carrie and DeMaster, David and Smith, Craig}, year={2008}, month={Nov}, pages={2415–2424} }
 @article{purinton_demaster_thomas_smith_2008, title={C-14 as a tracer of labile organic matter in Antarctic benthic food webs}, volume={55}, ISSN={["1879-0100"]}, DOI={10.1016/j.dsr2.2008.06.004}, abstractNote={14C measurements were made on surface plankton, particle-trap material, surface sediment, benthic invertebrate gut contents, and body tissue samples to assess the effectiveness of this radioisotope as a tracer of labile organic carbon in Antarctic benthic food webs. Samples were collected on five cruises to the West Antarctic Peninsula (WAP) shelf between November 1999 and March 2001 as part of the Food for Benthos on the ANtarctic Continental-Shelf (FOODBANCS) Project. The 14C contents of the body tissues from a variety of deposit feeders (−126±13 per mil) were substantially enriched relative to the surface sediment (−234±13 per mil) and statistically similar to the organic matter collected in plankton tows (−135±10 per mil), indicating that recently produced marine plankton are the primary source of nutrition for these deposit feeders on the West Antarctic shelf. Selective ingestion was the primary feeding strategy used by echiuran worms and certain holothurians (i.e. Peniagone vignoni) for incorporating labile organic carbon into their tissues as demonstrated by the large differences (105±13 per mil) between surface sediment and gut content 14C activities. In contrast, digestive and/or assimilatory selection was the predominant strategy used by an irregular urchin (Amphipneustes lorioli) and several other holothurians (Protelpidia murrayi, Bathyplotes fuscivinculum and the head-down conveyor belt feeder, Molpadia musculus), as demonstrated by large differences (42±7 per mil) between the 14C activities of their foregut or whole-gut organic contents and their body tissues. Despite large fluctuations in carbon export from the euphotic zone, benthic feeding strategies remained essentially constant over the 15-month sampling period. No seasonal variation was evident in either the 14C abundance of the deposit-feeder body tissues, or in the 14C abundance of their gut contents. The mean 14C abundance in the body tissues of the two sub-surface deposit feeders (A. lorioli and M. musculus; mean=−136.2±8.5 per mil) was distinct (p=0.0008) from the mean 14C abundance in the body tissues of the four surface deposit feeders (echiuran worm, P. vignoni, P. murrayi, and B. fusciviculum; −122.6±12.3 per mil). The mean 14C abundance of the gut contents from the sub-surface deposit feeders (−178.0±18.6 per mil) also was significantly depleted (p=0.0009) relative to that of the surface deposit feeders (−149.5±26.6 per mil). The 14C measurements proved to be a much more sensitive tracer for tracking labile organic carbon during ingestive and assimilatory processes than the stable isotopes of carbon or nitrogen.}, number={22-23}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Purinton, Brett L. and DeMaster, David J. and Thomas, Carrie J. and Smith, Craig R.}, year={2008}, month={Nov}, pages={2438–2450} }
 @article{gallinari_ragueneau_demaster_hartnett_rickert_thomas_2008, title={Influence of seasonal phytodetritus deposition on biogenic silica dissolution in marine sediments-Potential effects on preservation}, volume={55}, ISSN={["1879-0100"]}, DOI={10.1016/j.dsr2.2008.06.005}, abstractNote={The deposition of fresh phytoplankton detritus (phytodetritus) following phytoplankton blooms may influence biogenic silica (BSi) dissolution in marine sediments. We studied BSi dissolution properties before, during, and after periods of phytodetritus deposition during time-series field programs in the abyssal North Atlantic (the BENGAL project), and on the West Antarctic Peninsula Shelf (the FOODBANCS project). Dissolution experiments, performed by means of flow-through reactors, showed temporal variations in the dissolution properties of BSi in the sediment column after phytodetritus deposition. This non-steady-state character of benthic silica dynamics is an important aspect of pelagic–benthic coupling. The last FOODBANCS cruise occurred after a phytodetritus deposition event, and yielded high pore-water dissolved silica (DSi) concentrations and DSi effluxes in the upper centimetres of the sediment column, suggesting a rapid turnover of recently deposited siliceous material. Higher dissolution rates were measured in the phytodetritus-rich sediments relative to surface sediments collected during previous seasons on earlier FOODBANCS cruises. During the BENGAL project, high dissolution rates were measured at depth in the sediment column only after a summer phytodetritus deposition event. In the highly detrital sediment matrix of the abyssal North Atlantic Ocean, resolution of increased dissolution rates and experimental artefacts of the flow-through reactors can be difficult because of the low abundance of BSi. Depending on the sediment matrix, bioturbation can play a crucial role in transporting fresh BSi particles to depth, where DSi concentrations are close to experimentally determined BSi solubilities. The potential impacts of such processes on BSi preservation are discussed. We suggest that future models of BSi early diagenesis should include the rapid mixing of freshly deposited particles if we want to describe further the preservation of BSi in marine sediments.}, number={22-23}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Gallinari, M. and Ragueneau, O. and DeMaster, D. J. and Hartnett, H. and Rickert, D. and Thomas, C.}, year={2008}, month={Nov}, pages={2451–2464} }
 @article{smith_demaster_2008, title={Preface and brief synthesis for the FOODBANCS volume}, volume={55}, ISSN={["1879-0100"]}, DOI={10.1016/j.dsr2.2008.08.001}, abstractNote={In this volume we present results from the FOODBANCS Project, which examined the fate and benthic community impact of summer bloom material on the West Antarctic Peninsula shelf floor. The project involved a 5-cruise, 15-month time-series program in which sediment-trap moorings, core sampling, radiochemical profiling, sediment respirometry, bottom photography, and bottom trawling were used to evaluate: (1) seafloor deposition and lability of POC, (2) patterns of labile POC consumption and sediment mixing by benthos, and (3) seasonal and inter-annual variations in biotic abundance, biomass, reproductive condition, recruitment, and sediment community respiration. We find that the seafloor flux and accumulation of particulate organic carbon on the West Antarctic Peninsula shelf exhibit intense seasonal and interannual variability. Nonetheless, many key benthic processes, including organic-matter degradation, bioturbation, deposit feeding, and faunal abundance, reproduction and recruitment, show relatively muted response to this intense seasonal and inter-annual variability in export flux. We thus hypothesize that benthic ecosystems on the Antarctic shelf act as “low-pass” filters, and may be extremely useful in resolving the impacts of climatic change over periods of years to decades in Antarctic Peninsula region.}, number={22-23}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Smith, Craig R. and DeMaster, David J.}, year={2008}, month={Nov}, pages={2399–2403} }
 @article{mcclintic_demaster_thomas_smith_2008, title={Testing the FOODBANCS hypothesis: Seasonal variations in near-bottom particle flux, bioturbation intensity, and deposit feeding based on Th-234 measurements}, volume={55}, ISSN={["1879-0100"]}, DOI={10.1016/j.dsr2.2008.06.003}, abstractNote={Naturally occurring 234Th (24-d half-life) was used on the West Antarctic continental shelf to evaluate temporal variations in the flux of particulate material reaching the seabed, bioturbation intensity, the seasonal continuity of feeding by benthic fauna, and trends in particle selection during ingestion for six common detritivores (four surface deposit feeders and two subsurface deposit feeders). These measurements were made at three stations during the five FOODBANCS cruises (December 1999, March, June, and October 2000, and March 2001) to assess the nature of pelagic–benthic coupling on the shelf and to evaluate the seabed as a potential food bank for deposit feeders when surface primary production is minimal. Two summer regimes were sampled (March 2000 and March 2001) with the latter exhibiting a distinct 1–2-cm-thick phytodetritus layer in nearly all sediment core samples. At site B, the 234Th fluxes into the near-bottom (150/170 mab) sediment traps were indistinguishable for the December–March 2000, March–June 2000, and June–October 2000 sampling intervals (fluxes ranging from 170 to 280 dpm m−2 d−1). However, the sediment-trap 234Th flux measured for the October 2000–March 2001 interval (1000 dpm m−2 d−1) was ∼5-fold greater than during the other three sampling periods, consistent with the deposition of a phytodetritus layer. The steady-state 234Th fluxes derived from seabed inventories at site B were 2.4–2.7 times greater than the sediment-trap 234Th fluxes, indicating substantial scavenging of this particle-reactive radiotracer in the bottom 150 m of the water column and/or lateral transport near the seabed. The seabed 234Th inventories at the three stations showed no variation during the first four cruises, but were significantly greater during cruise FB-V (March 2001), when the phytodetritus layer occurred. Based on 234Th distributions in the seabed, bioturbation intensities (quantified using the diffusive mixing coefficient, Db) varied from 0.5 to 97 cm2 yr−1. Mixing coefficients were significantly lower during FB-II than during FB-III, but no other time comparisons were statistically significant (p>0.05). 234Th Dbs showed no distinct seasonality, and no correlation with either organic carbon flux into the sediment traps or 234Th inventory in the seabed. The four surface deposit feeders examined, an echiuran worm and three holothurians (Protelpidia murrayi, Bathyplotes fuscivinculum, and Peniagone vignoni), exhibited greater particle selection for recently deposited sediment during ingestion than the two subsurface deposit feeders studied (a head-down deposit feeding holothurian, Molpadia musculus, and an irregular urchin, Amphipneustes lorioli). All six deposit feeders contained excess 234Th activity in gut sediments during all five cruises, indicating sediment ingestion year round, even during the austral winter. The lack of seasonal variation in bioturbation intensity and the demonstration of year-round feeding in deposit feeders are consistent with the hypothesis that the seafloor sediments accumulate labile organic matter produced during periods of high primary production and that deposit feeders utilize this food source as a food bank on a year-round basis.}, number={22-23}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={McClintic, Mark A. and DeMaster, David J. and Thomas, Carrie J. and Smith, Craig R.}, year={2008}, month={Nov}, pages={2425–2437} }
 @article{smith_mincks_demaster_2008, title={The FOODBANCS project: Introduction and sinking fluxes of organic carbon, chlorophyll-a and phytodetritus on the western Antarctic Peninsula continental shelf}, volume={55}, ISSN={["1879-0100"]}, DOI={10.1016/j.dsr2.2008.06.001}, abstractNote={The impact of the highly seasonal Antarctic primary production cycle on shelf benthic ecosystems remains poorly evaluated. Here we describe a times-series research project on the West Antarctic Peninsula (WAP) shelf designed to evaluate the seafloor deposition, and subsequent ecological and biogeochemical impacts, of the summer phytoplankton bloom along a transect crossing the Antarctic shelf near Anvers Island. During this project, entitled Food for Benthos on the Antarctic Continental Shelf (FOODBANCS), we deployed replicate sediment traps 150–170 m above the seafloor (total water-column depth of 590 m) on the central shelf from December 1999 to March 2001, recovering trap samples every 3–4 months. In addition, we used a seafloor time-lapse camera system, as well as video surveys conducted at 3–4 months intervals, to monitor the presence and accumulation of phytodetritus at the sediment–water interface. The fluxes of particulate organic carbon and chlorophyll-a into sediment traps (binned over 3–4 month intervals) showed patterns consistent with seasonal variability, with average summer fluxes during the first year exceeding winter fluxes by a factor of ∼2–3. However, inter-annual variability in summer fluxes was even greater than seasonal variability, with 4–10-fold differences in the flux of organic carbon and chlorophyll-a between the summer seasons of 1999–2000 and 2000–2001. Phytodetrital accumulation at the shelf floor also exhibited intense inter-annual variability, with no visible phytodetritus from essentially December 1999 to November 2000, followed by pulsed accumulation of 1–2 cm of phytodetritus over a ∼30,000 km2 shelf area by March 2001. Comparisons with other studies suggest that the levels of inter-annual variability we observed are typical of the Antarctic shelf over decadal time scales. We conclude that fluxes of particulate organic carbon, chlorophyll-a and phytodetritus to WAP-shelf sediments vary intensely on seasonal to inter-annual time scales, yielding dramatic temporal variability in the flux of food for detritivores to the Antarctic shelf floor.}, number={22-23}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Smith, Craig R. and Mincks, Sarah and DeMaster, David J.}, year={2008}, month={Nov}, pages={2404–2414} }
 @article{bucci_rebach_demaster_showers_2007, title={A comparison of blue crab and bivalve delta N-15 tissue enrichment in two North Carolina estuaries}, volume={145}, DOI={10.1016/j.envpol.2006.03.009}, abstractNote={Stable isotope analyses (delta(15)N) were used to examine invertebrate tissue enrichment in two North Carolina estuaries with differing amounts of nutrient loading. Bivalves collected from a nutrient sensitive estuary yielded a significant difference in mean nitrogen isotopic composition of tissue (10.4 per thousand+/-0.82; N=66) compared to bivalves collected from a less nutrient sensitive estuary (6.4 per thousand+/-0.63; N=45). Similarly, blue crabs from nutrient sensitive sites had a nitrogen isotopic composition of 11.4 per thousand (+/-1.3, N=77), which was significantly different (P<0.001) than the tissue of less nutrient sensitive blue crabs (9.6 per thousand+/-0.6; N=77). The results showed that an inverse relationship exists between invertebrate tissue enrichment and indicators of water quality across estuarine sites. This study suggests that a relationship may exist between nutrient sources and subsequent energy transfer to estuarine consumers in two North Carolina estuaries.}, number={1}, journal={Environmental Pollution}, author={Bucci, J. P. and Rebach, S. and Demaster, D. and Showers, W. J.}, year={2007}, pages={299–308} }
 @article{khalil_rabouille_gallinari_soetaert_demaster_ragueneau_2007, title={Constraining biogenic silica dissolution in marine sediments: A comparison between diagenetic models and experimental dissolution rates}, volume={106}, ISSN={["1872-7581"]}, DOI={10.1016/j.marchem.2006.12.004}, abstractNote={The processes controlling preservation and recycling of particulate biogenic silica in sediments must be understood in order to calculate oceanic silica mass balances. The new contribution of this work is the coupled use of advanced models including reprecipitation and different phases of biogenic silica with different dissolution characteristics as well as new data sets concerning experimental dissolution rates of marine particles and sediment opal obtained in flow-through reactors. We have used three models representing early diagenesis of biogenic silica in sediments that calculate the vertical distributions of dissolved silicate and solid silica in sediments. Model 1 contains one type of biogenic silica and the dissolution rate is constant, whereas model 2 contains a variable dissolution rate constant with sediment depth (representing aging) and one type of biogenic silica. Model 3 incorporates aging by describing two types of biogenic silica that differ by their dissolution properties. An explicit term of reprecipitation is incorporated into the three models. The distributions of dissolved silicate and solid silica predicted by steady-state calculations are compared to 4 observed data sets, from the Southern Ocean, the Equatorial Pacific and the North Atlantic, covering a wide range of sediment compositions, from opal-rich to opal-poor sediments. After adjustment of the critical parameters (the apparent silica dissolution rate constants, the biogenic silica flux deposited at the sediment–water interface and the reprecipitation rate), the second and third models provide good agreements between predicted and measured dissolved Si and solid silica profiles for each data set, except for the second model in the Equatorial Pacific. However, a large discrepancy between the experimentally derived dissolution rate constants and those calculated by the models is observed at all sites at depth in the sediment, suggesting that either artifacts arise during dissolution experiments such as over-representation of rapidly dissolving silica or variation of dissolution properties during the experimental procedures or the model oversimplifies the processes associated to silica dissolution and alumino-silicate reprecipitation and their interaction.}, number={1-2}, journal={MARINE CHEMISTRY}, author={Khalil, K. and Rabouille, C. and Gallinari, M. and Soetaert, K. and DeMaster, D. J. and Ragueneau, O.}, year={2007}, month={Jul}, pages={223–238} }
 @article{bucci_showers_rebach_demaster_genna_2007, title={Stable isotope analyses (delta N-15 and delta C-13) of the trophic relationships of Callinectes sapidus in two north Carolina estuaries}, volume={30}, ISSN={["1559-2731"]}, DOI={10.1007/BF02841395}, number={6}, journal={ESTUARIES AND COASTS}, author={Bucci, J. P. and Showers, W. J. and Rebach, S. and DeMaster, D. and Genna, B.}, year={2007}, month={Dec}, pages={1049–1059} }
 @article{smith_mincks_demaster_2006, title={A synthesis of bentho-pelagic coupling on the Antarctic shelf: Food banks, ecosystem inertia and global climate change}, volume={53}, ISSN={["1879-0100"]}, DOI={10.1016/j.dsr2.2006.02.001}, abstractNote={The Antarctic continental shelf is large, deep (500–1000 m), and characterized by extreme seasonality in sea-ice cover and primary production. Intense seasonality and short pelagic foodwebs on the Antarctic shelf may favor strong bentho-pelagic coupling, whereas unusual water depth combined with complex topography and circulation could cause such coupling to be weak. Here, we address six questions regarding the nature and strength of coupling between benthic and water-column processes on the continental shelf surrounding Antarctica. We find that water-column production is transmitted to the shelf floor in intense pulses of particulate organic matter, although these pulses are often difficult to correlate with local phytoplankton blooms or sea-ice conditions. On regional scales, benthic habitat variability resulting from substrate type, current regime, and iceberg scour often may obscure the imprint of water-column productivity on the seafloor. However, within a single habitat type, i.e. the muddy sediments that characterize much of the deep Antarctic shelf, macrobenthic biomass appears to be correlated with regional primary production and sea-ice duration. Over annual time-scales, many benthic ecological processes were initially expected to vary in phase with the extraordinary boom/bust cycle of production in the water column. However, numerous processes, including sediment respiration, deposit feeding, larval development, and recruitment, often are poorly coupled to the summer bloom season. Several integrative, time-series studies on the Antarctic shelf suggest that this lack of phasing may result in part from the accumulation of a persistent sediment food bank that buffers the benthic ecosystem from the seasonal variability of the water column. As a consequence, a variety of benthic parameters (e.g., sediment respiration, inventories of labile organic matter, macrobenthic biomass) may act as “low-pass” filters, responding to longer-term (e.g., inter-annual) trends in water-column production. Bentho-pelagic coupling clearly will be altered by Antarctic climate change as patterns of sea-ice cover and water-column recycling vary. However, the nature of such climate-driven changes will be very difficult to predict without further studies of Antarctic benthic ecosystem response to (1) inter-annual variability in export flux, and (2) latitudinal gradients in duration of sea-ice cover and benthic ecosystem function.}, number={8-10}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Smith, Craig R. and Mincks, Sarah and DeMaster, David J.}, year={2006}, pages={875–894} }
 @article{liu_li_xu_velozzi_yang_milliman_demaster_2006, title={Sedimentary features of the Yangtze River-derived along-shelf clinoform deposit in the East China Sea}, volume={26}, ISSN={0278-4343}, url={http://dx.doi.org/10.1016/j.csr.2006.07.013}, DOI={10.1016/j.csr.2006.07.013}, abstractNote={A predominant sigmoidal clinoform deposit extends from the Yangtze River mouth southwards 800 km along the Chinese coast. This clinoform is thickest (∼40 m) between the 20 and 30 m isobaths and progressively thins offshore, reaching water depths of 60 and 90 m and distances up to 100 km offshore. Clay mineral, heavy metal, geochemical and grain-size analyses indicate that the Yangtze River is the primary source for this longshore-transported clinoform deposit. 210Pb chronologies show the highest accumulation rates (>3 cm/yr) occur immediately adjacent to the Yangtze subaqueous delta (north of 30 °N), decreasing southward alongshore and eastward offshore. The interaction of strong tides, waves, the China Coastal Current, winter storms, and offshore upwelling appear to have played important roles in trapping most Yangtze-derived sediment on the inner shelf and transporting it to the south.}, number={17-18}, journal={Continental Shelf Research}, publisher={Elsevier BV}, author={Liu, J.P. and Li, A.C. and Xu, K.H. and Velozzi, D.M. and Yang, Z.S. and Milliman, J.D. and DeMaster, D.J.}, year={2006}, month={Nov}, pages={2141–2156} }
 @article{mincks_smith_demaster_2005, title={Persistence of labile organic matter and microbial biomass in Antarctic shelf sediments: evidence of a sediment 'food bank'}, volume={300}, journal={Marine Ecology Progress Series}, author={Mincks, S. L. and Smith, C. R. and Demaster, D. J.}, year={2005}, pages={19-} }
 @article{beek_reyss_demaster_paterne_2004, title={Ra-226-in marine barite: relationship with carbonate dissolution and sediment focusing in the equatorial Pacific}, volume={51}, ISSN={["0967-0637"]}, DOI={10.1016/j.dsr.2003.10.007}, abstractNote={Sedimentation rates were determined from the 226Ra (T1/2=1602a) decay in barite in seven cores collected from the western, central and eastern equatorial Pacific. Timing of the last carbonate dissolution increase was investigated with this new chronometer. However, an unconformity in the 226Ra-in-barite profiles was observed at some sites, which could be related to this carbonate dissolution event. We discuss different mechanisms that may have generated these unconformities, including (1) bioturbation, (2) possible bias in the estimate of the correction for supported 226Ra activities, (3) changes in the 226Ra/Ba ratio within surface waters and (4) processes that may have affected the 226Ra/Ba ratio recorded in barite, either within the water column or at the sediment–water interface. Among the processes invoked, an increase in the sediment focusing during the Holocene constitutes the mechanism that can most likely explain the observed unconformities. An increase in the sediment redistribution by bottom currents would enhance the lateral transport of old resuspended barite crystals (with a low 226Ra/Ba ratio). The 226Ra/Ba ratio of barite that accumulates in the sediments, therefore, may have decreased, leading to the unconventional 226Ra-profile shape observed in several cores. A change in the chemistry of the bottom waters that transport the resuspended sediment may have also affected the sediment carbonate contents.}, number={2}, journal={DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS}, author={Beek, P and Reyss, JL and DeMaster, D and Paterne, M}, year={2004}, month={Feb}, pages={235–261} }
 @article{demopoulos_smith_demaster_fornes_2003, title={Evaluation of excess Th-234 activity in sediments as an indicator of food quality for deep-sea deposit feeders}, volume={61}, ISSN={["1543-9542"]}, DOI={10.1357/002224003322005096}, abstractNote={Deep-sea deposit feeders selectively ingest large volumes of sediment. Knowledge of the nature of this selectivity will help to elucidate the limiting nutritional requirements and geochemical impacts of these abundant animals. Shallow-water and theoretical studies suggest that deep-sea deposit feeders should select particles rich in protein, bacterial biomass, and/or chloropigment concentrations. Recent studies indicate that deep-sea megafaunal deposit feeders exhibit strong gut enrichment of excess (xs) 234 Th activity, even though 234 Thxs lacks nutritional value. To explore the significance of selective ingestion of 234 Thxs activity, we evaluated the correlations between 234 Thxs activity and three potential tracers of deposit feeder food quality: chlorophyll a (chl a), enzymatically hydrolyzable amino acids (EHAA), and adenosine triphosphate (ATP). Surface sediments from three quiescent bathyal basins off Southern California (San Nicolas, Santa Catalina, and San Clemente) were collected by a multiple corer and analyzed for 234 Thxs activity, chl a, EHAA, ATP, and total organic carbon and nitrogen. 234 Thxs activity was positively correlated with chl a and phaeopigment concentrations and negatively correlated with EHAA concentrations. Excess 234 Th was not linearly correlated with concentrations of ATP, organic carbon, or total nitrogen. The results suggest that deep-sea deposit feeders select sediments with high 234 Thxs activity because it is associated with recently settled phytodetrital material. There is no evidence that this 234 Thxs-rich material has particularly high concentrations of labile amino acids or microbial biomass. Phytodetrital material may be an important source of some other limiting nutrient to deep-sea deposit feeders, e.g., polyunsaturated fatty acids, labile organic carbon and/or vitamins.}, number={2}, journal={JOURNAL OF MARINE RESEARCH}, author={Demopoulos, AWJ and Smith, CR and DeMaster, DJ and Fornes, WL}, year={2003}, month={Mar}, pages={267–284} }
 @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{mayer_benninger_bock_demaster_roberts_martens_2002, title={Mineral associations and nutritional quality of organic matter in shelf and upper slope sediments off Cape Hatteras, USA: a case of unusually high loadings}, volume={49}, ISSN={["0967-0645"]}, DOI={10.1016/S0967-0645(02)00130-3}, abstractNote={Relationships among organic carbon (OC), enzymatically hydrolyzable amino acid (EHAA) concentrations and mineral surface area (SFA) were assessed for sediments from the shelf and slope region near Cape Hatteras, USA. Grain size, measured here as mineral-specific surface area, explained 55% of the variance in organic matter concentrations. Organic loadings, as ratios of organic carbon to surface area (OC:SFA), decrease with water column and core depth. OC:SFA ratios in this region are comparable to those found in areas with anoxic water columns, and are the highest reported for shelf-slope sediments underlying oxygenated water columns. With increasing water-column depth, organic matter becomes progressively incorporated into low-density (<2.4 g cm−3), organomineral aggregates, reflecting the increase in clay content in sediments with water-column depth. Organic coverage of mineral surfaces was determined by gas sorption methods; throughout the depth range minerals are essentially bare of organic coatings, in spite of high organic loadings. EHAA concentrations increase with water-column depth in a similar fashion as OC concentrations, and help to support intense heterotrophic communities at depth. Rapidly decreasing ratios of EHAA to total organic matter with water-column depth are consistent with previous inferences that largely refractory organic matter is exported from the shelf to the slope. Significant burial of EHAA downcore indicates protection of enzymatically hydrolyzable biopolymers with depth.}, number={20}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Mayer, L and Benninger, L and Bock, M and DeMaster, D and Roberts, Q and Martens, C}, year={2002}, pages={4587–4597} }
 @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{verity_bauer_flagg_demaster_repeta_2002, title={The Ocean Margins Program: an interdisciplinary study of carbon sources, transformations, and sinks in a temperate continental margin system}, volume={49}, ISSN={["1879-0100"]}, DOI={10.1016/S0967-0645(02)00120-0}, abstractNote={The cycling of carbon on the US east coast shelf and upper slope has been studied for 20 years in a variety of interdisciplinary programs focused on the Mid and South Atlantic Bights. The culmination of this research was a comprehensive field study conducted in 1996 to ascertain whether the Cape Hatteras shelf was a net source or sink for atmospheric CO2, and the associated transformations and pathways of inorganic and organic carbon. The rationale, objectives, design, and overview of the Ocean Margins Program are given here as a framework to interpret the results of the papers presented in this special issue.}, number={20}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Verity, PG and Bauer, JE and Flagg, CN and DeMaster, DJ and Repeta, DJ}, year={2002}, pages={4273–4295} }
 @article{demaster_2002, title={The accumulation and cycling of biogenic silica in the Southern Ocean: revisiting the marine silica budget}, volume={49}, ISSN={["0967-0645"]}, DOI={10.1016/S0967-0645(02)00076-0}, abstractNote={In many of the recent marine silica budgets (e.g., Science 268 (1995) 375), a majority of the world's biogenic silica accumulation is attributed to the siliceous-ooze deposits in the Antarctic deep sea. Based on 230Th-normalized sediment accumulation rates as well as comparative studies of silica preservation (seabed accumulation compared to surface biogenic production), the rate of biogenic silica accumulation in Antarctic siliceous-ooze deposits has been over-estimated by as much as 35%. The current estimate for silica accumulation in these high-latitude deposits is 3.1×1012 mol yr−1 (as compared to previous values of 4.1–4.8×1012 mol yr−1). To maintain balance between silicate supply and biogenic silica removal in the oceans, an additional repository is needed. Evidence from continental shelf and upper slope sediments suggests that biogenic silica accumulation in continental margin deposits may account for a much larger fraction of the marine silica burial than previously thought, compensating for the diminished accumulation in the Antarctic deep sea. If biogenic silica accumulation in continental margin sediments replaces nearly a third of the silica accumulation in the Antarctic deep sea, the marine cycles of organic matter and biogenic silica are coupled to a greater extent than reported in previous budgets. Plusieurs travaux récents (e.g. The silica balance in the world ocean: A re-estimate. Science, 268, 375-379) montrent que la majorité des dépots sédimentaires de silice biogéne (=opale) de l’océan mondial intervient dans l’Océan Antarctique abyssal. En normalisant les vitesses d’accumulation des sédiments par la technique au 230 Th nous montrons que le flux d’accumulation de l’opale dans l’Antarctique est de 3,1 E12 moles par an, soit de 35% inférieur aux estimations antérieures (4,1 à 4,8 E12 mol par an). Si les apports nets de silicium dans l’océan sont compensés par les dépots nets d’opale biogéne (hypothèse du cycle du silicium à l’état stationnaire) un autre puite d’opale doit exister dans l’océan. Nos données tendent à montrer que ce puits pourrait se trouver dans les marges continentales de l’océan mondial, contrairement à ce que l’on pensait jusqu’à présent. Si l’accumulation d’opale dans ces marges remplace environ 1/3 du dépot sédimentaire abyssal en Antarctique, ceci signifie que les cycles océanique de la matière organique et de la silice biogène sont plus couplés qu’il n’était généralement admis.}, number={16}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={DeMaster, DJ}, year={2002}, pages={3155–3167} }
 @article{fornes_demaster_smith_2001, title={A particle introduction experiment in Santa Catalina Basin sediments: Testing the age-dependent mixing hypothesis}, volume={59}, ISSN={["0022-2402"]}, DOI={10.1357/002224001321237380}, abstractNote={The occurrence of age-dependent mixing, a process by which recently deposited, food-rich particles undergo more intense bioturbation than older, food-poor particles, could dramatically alter patterns of organic-matter diagenesis in deep-sea sediments. To explicitly test for age-dependent mixing, an in-situ particle introduction experiment was conducted on the bathyal Santa Catalina Basin floor. Mixtures of radioisotope-tagged particles representing a food quality gradient were dispersed in small amounts on the seafloor and sampled over periods of 0 to 594 days. Introduced particle types were all similar in size and included fresh diatoms (young particles), surface sediments (intermediate-age particles), and particles from 30-cm deep in the sediment column (old particles). This approach permitted evaluation of particle mixing intensity for several particle ages and provided an independent check on mixing coefficients determined from naturally occurring radioisotopes ( 234 Th xs and 210 Pb xs ). All particles experienced rapid (<6 h) transport into the upper 2 cm of the seabed resulting from passive deposition down burrows or extremely rapid bioturbation. Intense bioturbation on 4-d time scales included both biodiffusive and nondiffusive (bioadvective and nonlocal) transport. Bioturbation of tracers exhibited time (or age) dependence in two ways: (1) Diffusive mixing intensity for all tracer types decreased with time (4-d D b = 293 cm 2 y -1 , D b at 520 d = 2.6 cm 2 y -1 ), and (2) The nature of bioturbation changed over this period with more efficient bioadvection and nonlocal exchange giving way to slower diffusive mixing. Both changes are consistent with the age-dependent-mixing hypothesis. Biodiffusive mixing was not measurably selective, with no significant preference for a single particle type. In contrast, nondiffusive transport, likely caused by deposit-feeding cirratulid polychaetes, exhibited distinct particle selectivity, especially over 4-d time scales, with the diatom tracer transported most rapidly to depth. Degradation of the labile organic carbon in diatoms most likely led to decreasing selection of diatoms by deposit feeders until diatoms and old sediment particles experienced comparable mixing intensities.}, number={1}, journal={JOURNAL OF MARINE RESEARCH}, author={Fornes, WL and DeMaster, DJ and Smith, CR}, year={2001}, month={Jan}, pages={97–112} }
 @misc{ragueneau_treguer_leynaert_anderson_brzezinski_demaster_dugdale_dymond_fischer_francois_et al._2000, title={A review of the Si cycle in the modem ocean: recent progress and missing gaps in the application of biogenic opal as a paleoproductivity proxy}, volume={26}, ISSN={["1872-6364"]}, DOI={10.1016/S0921-8181(00)00052-7}, abstractNote={Due to the major role played by diatoms in the biological pump of CO2, and to the presence of silica-rich sediments in areas that play a major role in air–sea CO2 exchange (e.g. the Southern Ocean and the Equatorial Pacific), opal has a strong potential as a proxy for paleoproductivity reconstructions. However, because of spatial variations in the biogenic silica preservation, and in the degree of coupling between the marine Si and C biogeochemical cycles, paleoreconstructions are not straitghtforward. A better calibration of this proxy in the modern ocean is required, which needs a good understanding of the mechanisms that control the Si cycle, in close relation to the carbon cycle. This review of the Si cycle in the modern ocean starts with the mechanisms that control the uptake of silicic acid (Si(OH)4) by diatoms and the subsequent silicification processes, the regulatory mechanisms of which are uncoupled. This has strong implications for the direct measurement in the field of the kinetics of Si(OH)4 uptake and diatom growth. It also strongly influences the Si:C ratio within diatoms, clearly linked to environmental conditions. Diatoms tend to dominate new production at marine ergoclines. At depth, they also succeed to form mats, which sedimentation is at the origin of laminated sediments and marine sapropels. The concentration of Si(OH)4 with respect to other macronutrients exerts a major influence on diatom dominance and on the rain ratio between siliceous and calcareous material, which severely impacts surface waters pCO2. A compilation of biogenic fluxes collected at about 40 sites by means of sediment traps also shows a remarkable pattern of increasing BSi:Corg ratio along the path of the “conveyor belt”, accompanying the relative enrichment of waters in Si compared to N and P. This observation suggests an extension of the Si pump model described by Dugdale and Wilkerson (Dugdale, R.C., Wilkerson, F.P., 1998. Understanding the eastern equatorial Pacific as a continuous new production system regulating on silicate. Nature 391, 270–273.), giving to Si(OH)4 a major role in the control of the rain ratio, which is of major importance in the global carbon cycle. The fate of the BSi produced in surface waters is then described, in relation to Corg, in terms of both dissolution and preservation mechanisms. Difficulties in quantifying the dissolution of biogenic silica in the water column as well as the sinking rates and forms of BSi to the deep, provide evidence for a major gap in our understanding of the mechanisms controlling the competition between retention in and export from surface waters. The relative influences of environmental conditions, seasonality, food web structure or aggregation are however explored. Quantitatively, assuming steady state, the measurements of the opal rain rate by means of sediment traps matches reasonably well those obtained by adding the recycling and burial fluxes in the underlying abyssal sediments, for most of the sites where such a comparison is possible. The major exception is the Southern Ocean where sediment focusing precludes the closing of mass balances. Focusing in fact is also an important aspect of the downward revision of the importance of Southern Ocean sediments in the global biogenic silica accumulation. Qualitatively, little is known about the duration of the transfer through the deep and the quality of the material that reaches the seabed, which is suggested to represent a major gap in our understanding of the processes governing the early diagenesis of BSi in sediments. The sediment composition (special emphasis on Al availability), the sedimentation rate or bioturbation are shown to exert an important control on the competition between dissolution and preservation of BSi in sediments. It is suggested that a primary control on the kinetic and thermodynamic properties of BSi dissolution, both in coastal and abyssal sediments, is exerted by water column processes, either occuring in surface waters during the formation of the frustules, or linked to the transfer of the particles through the water column, which duration may influence the quality of the biogenic rain. This highlights the importance of studying the factors controlling the degree of coupling between pelagic and benthic processes in various regions of the world ocean, and its consequences, not only in terms of benthic biology but also for the constitution of the sediment archive. The last section, first calls for the end of the “NPZD” models, and for the introduction of processes linked to the Si cycle, into models describing the phytoplankton cycles in surface waters and the early diagenesis of BSi in sediments. It also calls for the creation of an integrated 1-D diagnostic model of the Si:C coupling, for a better understanding of the interactions between surface waters, deep waters and the upper sedimentary column. The importance of Si(OH)4 in the control of the rain ratio and the improved parametrization of the Si cycle in the 1-D diagnostic models should lead to a reasonable incorporation of the Si cycle into 3-D regional circulation models and OGCMs, with important implications for climate change studies and paleoreconstructions at regional and global scale.}, number={4}, journal={GLOBAL AND PLANETARY CHANGE}, author={Ragueneau, O and Treguer, P and Leynaert, A and Anderson, RF and Brzezinski, MA and DeMaster, DJ and Dugdale, RC and Dymond, J and Fischer, G and Francois, R and et al.}, year={2000}, month={Dec}, pages={317–365} }
 @article{miller_smith_demaster_fornes_2000, title={Feeding selectivity and rapid particle processing by deep-sea megafaunal deposit feeders: A Th-234 tracer approach}, volume={58}, ISSN={["1543-9542"]}, DOI={10.1357/002224000321511061}, abstractNote={Deposit-feeding megafauna occur in virtually all deep-sea environments, yet their feeding selectivity and particle processing rates are poorly known. Excess 234 Th activity is commonly used as a geochemical tracer for recently settled (<100-d old) particles in the quiescent deep sea, but it has rarely been applied to the study of deposit feeders. To explore the selectivity and rates of megafaunal deposit feeding, we compared excess 234 Th activities in the gut contents of deposit feeders from Santa Catalina Basin (SCB) (∼1200 m depth) and the Hawaiian slope (∼1680 m) to the activity of surface sediments and, in SCB, to material from sediment traps moored ∼150 m above the seafloor. We also measured concentrations of chlorophyll a and phaeopigments in animal guts and surface sediments to evaluate feeding selectivity. In the SCB, excess 234 Th ( 234 Th xs ) activities in the guts of four species of surface-deposit feeders were 14-17 fold greater than those of the top 5 mm of sediment. Pannychia moseleyi and Scotoplanes globosa, two highly mobile, surface-deposit-feeding elasipodid holothurians, were the most enriched in gut 234 Th xs activity, suggesting that these species fed very selectively on particles settled to the seafloor within the previous ∼20 d. Pannychia moseleyi guts also exhibited 500-fold enrichment of chlorophyll a relative to surface sediments indicating highly selective ingestion of phytodetritus. Chiridota sp., a burrowing, surface-deposit-feeding, chiridotid holothurian, and Bathybembix bairdii, a surface-deposit-feeding trochid gastropod, were less enriched in gut 234 Th xs activity, reflecting lower mobility and/or less selectivity at time of particle pickup. A subsurface-deposit-feeding, molpadiid holothurian was not enriched in gut 234 Th xs activity compared to surface sediments, but was greatly enriched compared to average activities at its presumed feeding depth of 6-7 cm. On the Hawaiian slope, gut contents of two surface-deposit feeders, the synallactid holothurians Mesothuria carnosa and Paleopatides retifer, were not enriched in 234 Th xs activity; however, M. carnosa and Phryssocystis sp. (a surface-deposit-feeding echinoid) were enriched in chlorophyll a, suggesting that the Hawaiian slope species are also selective feeders. Presumably, frequent sediment resuspension makes 234 Th xs activity a poor tracer for recently settled, food-rich particles on the Hawaiian slope. Based on a newly developed 234 Th-flux model, we calculate that the three dominant megafaunal, surface-deposit feeders in SCB consumed on average 39-52% (s.e. 13-27%) of the daily flux of 234 Th xs activity to the SCB floor. By chemically altering (e.g., digesting) and redistributing recently settled particulate organic matter, these megafauna are likely to substantially influence carbon diagenesis and food-web structure in this bathyal habitat.}, number={4}, journal={JOURNAL OF MARINE RESEARCH}, author={Miller, RJ and Smith, CR and DeMaster, DJ and Fornes, WL}, year={2000}, month={Jul}, pages={653–673} }
 @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{andrews_domack_cunningham_leventer_licht_jull_demaster_jennings_1999, title={Problems and possible solutions concerning radiocarbon dating of surface marine sediments, Ross Sea, Antarctica}, volume={52}, ISSN={["0033-5894"]}, DOI={10.1006/qres.1999.2047}, abstractNote={Radiocarbon accelerator mass spectrometric (AMS) dates on the acid-insoluble fraction from 38 core tops from the western Ross Sea, Antarctica, are used to address these questions: (1) What are the apparent ages of sediments at or close to the present sediment/water interface? (2) Is there a statistically significant pattern to the spatial distribution of core top ages? and (3) Is there a “correction factor” that can be applied to these age determinations to obtain the best possible Holocene (downcore) chronologies? Ages of core top sediments range from 2000 to 21,000 14C yr B.P. Some “old” core top dates are from piston cores and probably represent the loss of sediment during the coring process, but some core top samples >6000 14C yr B.P. may represent little or no Holocene deposition. Four possible sources of variability in dates ≤6000 14C yr B.P. (n = 28) are associated with (1) different sample preparation methods, (2) different sediment recovery systems, (3) different geographic regions, and (4) within-sample lateral age variability. Statistical analysis on an a posteriori design indicates that geographic area is the major cause of variability; there is a difference in mean surface sediment age of nearly 2000 yr between sites in the western Ross Sea and sites east of Ross Bank in south-central Ross Sea. The systematic variability in surface age between areas may be attributed to: (a) variable sediment accumulation rates (SAR) (surface age is inversely related to SAR), (b) differences in the percentage of reworked (dead) carbon between each area, and/or (c) differences in the CO2 exchange between the ocean and the atmosphere.}, number={2}, journal={QUATERNARY RESEARCH}, author={Andrews, JT and Domack, EW and Cunningham, WL and Leventer, A and Licht, KJ and Jull, AJT and DeMaster, DJ and Jennings, AE}, year={1999}, month={Sep}, pages={206–216} }
 @article{berelson_anderson_dymond_demaster_hammond_collier_honjo_leinen_mcmanus_pope_et al._1997, title={Biogenic budgets of particle rain, benthic remineralization and sediment accumulation in the equatorial Pacific}, volume={44}, ISSN={["0967-0645"]}, DOI={10.1016/S0967-0645(97)00030-1}, abstractNote={Budgets of organic C (Corg), CaC03 and opal have been constructed for the Palisades, NY Pacific equatorial region at 140°W between 5°N and 5°S. Measurements of the rain and benthic remineralization rate of biogenic materials have been adjusted and normalized to account for sampling biases. Sea surface temperature serves as a master variable in normalizing sediment trap and benthic remineralization data to average conditions. The rain and remineralization rates for Corg are nearly equal: 0.40±0.05 and 0.46±0.06 mmol m−2 d−1 respectively; thus only a minor fraction of this constituent is buried. Rain and dissolution rates for biogenic opal are similarly balanced (0.3±0.06 and 0.36±0.01 mmol m−2 d−1) and consistent with the value for opal burial (0.0±0.004). The CaC03 budget appears to have changed during the Holocene. The best estimates of modern CaC03 dissolution (0.58±0.03 mmol m−2 d−1) and rain rate (0.61±0.06) are consistent with230Th-normalized carbonate accumulation rates for the late Holocene (0.1 mmol m−2 d−1). However, the balance between dissolution and rain is not consistent with early Holocene carbonate accumulation (0.3 mmol m−2 d−1 ), and this imbalance suggests: 1) a recent increase in the rate of CaC03 dissolution on the sea floor, or 2) a decrease in the rain rate of carbonate particles. Modeling230Th profiles in sediments from this region define the last 3000 years as the duration of increased dissolution or decreased particle rain. 231Pa/230Th ratios in sediments indicate that particle rain rates have remained constant or possibly increased slightly through the Holocene. Two potential causes for increased dissolution were investigated; a change in deep water carbonate saturation or a change in Co,g/CaC03 rain ratios. A model describing carbonate dissolution as a function of the degree of undersaturation and the amount of organic carbon oxidation within sediments indicates that the recent increase in dissolution is more likely due to changes in bottom water chemical composition. We propose that Pacific Ocean bottom water carbonate ion concentration has decreased by 10–15 μM over the last 3000 years.}, number={9-10}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Berelson, WM and Anderson, RF and Dymond, J and Demaster, D and Hammond, DE and Collier, R and Honjo, S and Leinen, M and Mcmanus, J and Pope, R and et al.}, year={1997}, pages={2251–2282} }
 @article{smith_berelson_demaster_dobbs_hammond_hoover_pope_stephens_1997, title={Latitudinal variations in benthic processes in the abyssal equatorial Pacific: control by biogenic particle flux}, volume={44}, ISSN={["0967-0645"]}, DOI={10.1016/S0967-0645(97)00022-2}, abstractNote={The equatorial Pacific forms a band of high, globally significant primary production. This productivity drops off steeply with distance from equatorial upwelling, yielding large latitudinal gradients in biogenic particle flux to the abyssal seafloor. As part of the US JGOFS Program, we studied the translation of these particle-flux gradients into the benthic ecosystem from 12°S to 9°N along 135–140°W to evaluate their control of key benthic processes, and to evaluate sediment proxies of export production from overlying waters. In October–December 1992 the remineralization rates of organic carbon, calcium carbonate and biogenic opal roughly matched the rain rates of these materials into deep sediment traps, exhibiting peak values within 3° of the equator. Rates of bioturbation near the equator were about ten-fold greater than at 9°N, and appeared to exhibit substantial dependence on particulate-organic-carbon flux, tracer time scale (i.e. age-dependent mixing), and pulsed mixing from burrowing urchins. Organic-carbon degradation within sediments near the equator was dominated by a very labile component (reaction rate constant, k approximately 15 per year) that appeared to be derived from greenish phytodetritus accumulated on the seafloor. Organic-carbon degradation at the highest latitudes was controlled by a less reactive component, with a mean k of approximately 0.075 per year. Where measured, megafaunal and macrofaunal abundances were strongly correlated with annual particulate-organic carbon flux; macrofaunal abundance in particular might potentially serve as a proxy for export production in low-energy abyssal habitats. Sedimentary microbial biomass also was correlated with the rain rate of organic carbon, but less strongly than larger biota and on shorter time scales (i.e. approximately 100 days). We conclude that the vertical flux of biogenic particlues exerts tight control on the nature and rates of benthic biological and chemical processes in the abyssal equatorial Pacific, and suggest that global changes in productivity on decadal or greater time scales could yield profound changes in deep-sea benthic ecoystems.}, number={9-10}, journal={DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, author={Smith, CR and Berelson, W and Demaster, DJ and Dobbs, FC and Hammond, D and Hoover, DJ and Pope, RH and Stephens, M}, year={1997}, pages={2295-+} }
 @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} }
 @article{treguer_nelson_vanbennekom_demaster_leynaert_queguiner_1995, title={THE SILICA BALANCE IN THE WORLD OCEAN - A REESTIMATE}, volume={268}, ISSN={["0036-8075"]}, DOI={10.1126/science.268.5209.375}, abstractNote={The net inputs of silicic acid (dissolved silica) to the world ocean have been revised to 6.1 � 2.0 teramoles of silicon per year (1 teramole = 1012 moles). The major contribution (about 80 percent) comes from rivers, whose world average silicic acid concentration is 150 micromolar. These inputs are reasonably balanced by the net ouputs of biogenic silica of 7.1 � 1.8 teramoles of silicon per year in modern marine sediments. The gross production of biogenic silica (the transformation of dissolved silicate to particulate skeletal material) in surface waters was estimated to be 240 � 40 teramoles of silicon per year, and the preservation ratio (opal accumulation in sediment/gross production in surface waters) averages 3 percent. In the world ocean the residence time of silicon, relative to total biological uptake in surface waters, is about 400 years.}, number={5209}, journal={SCIENCE}, author={TREGUER, P and NELSON, DM and VANBENNEKOM, AJ and DEMASTER, DJ and LEYNAERT, A and QUEGUINER, B}, year={1995}, month={Apr}, pages={375–379} }