@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{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{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} }