David J. DeMaster

article

A seismic study of the Mekong subaqueous delta: Proximal versus distal sediment accumulation

J. Paul Liu, David J. DeMaster, Charles A. Nittrouer, Emily F. Eidam, more

Continental Shelf Research > 2017 > 147 > C > 197-212

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...

article

Porewater advection of ammonium into the Neuse River Estuary, North Carolina, USA

Kimberly A. Null, D. Reide Corbett, David J. DeMaster, JoAnn M. Burkholder, more

Estuarine, Coastal and Shelf Science > 2011 > 95 > 2-3 > 314-325

Radon-222 ( ²²² Rn) and ammonium (NH ₄ ⁺ ) were measured in interstitial water of the Neuse River Estuary (NRE), North Carolina, USA to determine the advective flux of NH ₄ ⁺ from sediments to the overlying water column. Porewater samples were collected over an annual cycle from multi-level piezometers installed in nearshore sites. NH ₄ ⁺ concentrations...

article

Preface and brief synthesis for the FOODBANCS volume

Craig R. Smith, David J. DeMaster

Deep-Sea Research Part II > 2008 > 55 > 22-23 > 2399-2403

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:...

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Testing the FOODBANCS hypothesis: Seasonal variations in near-bottom particle flux, bioturbation intensity, and deposit feeding based on 234Th measurements

Mark A. McClintic, David J. DeMaster, Carrie J. Thomas, Craig R. Smith

Deep-Sea Research Part II > 2008 > 55 > 22-23 > 2425-2437

Naturally occurring ²³⁴ Th (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...

article

The FOODBANCS project: Introduction and sinking fluxes of organic carbon, chlorophyll-a and phytodetritus on the western Antarctic Peninsula continental shelf

Craig R. Smith, Sarah Mincks, David J. DeMaster

Deep-Sea Research Part II > 2008 > 55 > 22-23 > 2404-2414

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...

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14C as a tracer of labile organic matter in Antarctic benthic food webs

Brett L. Purinton, David J. DeMaster, Carrie J. Thomas, Craig R. Smith

Deep-Sea Research Part II > 2008 > 55 > 22-23 > 2438-2450

¹⁴ C 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...

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A synthesis of bentho-pelagic coupling on the Antarctic shelf: Food banks, ecosystem inertia and global climate change

Craig R. Smith, Sarah Mincks, David J. DeMaster

Deep-Sea Research Part II > 2006 > 53 > 8-10 > 875-894

The Antarctic continental shelf is large, deep (500–1000m), 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...

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The accumulation and cycling of biogenic silica in the Southern Ocean: revisiting the marine silica budget

David J. DeMaster

Deep-Sea Research Part II > 2002 > 49 > 16 > 3155-3167

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 ² ³ ⁰ Th-normalized sediment accumulation rates as well as comparative studies of silica preservation (seabed accumulation compared to surface biogenic production), the rate...

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Problems and Possible Solutions Concerning Radiocarbon Dating of Surface Marine Sediments, Ross Sea, Antarctica

John T. Andrews, Eugene W. Domack, Wendy L. Cunningham, Amy Leventer, more

Quaternary Research > 1999 > 52 > 2 > 206-216

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...

article

Latitudinal variations in benthic processes in the abyssal equatorial Pacific: control by biogenic particle flux

Craig R. Smith, Will Berelson, David J. Demaster, Fred C. Dobbs, more

Deep-Sea Research Part II > 1997 > 44 > 9-10 > 2295-2317

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...

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The behavior of particle-reactive tracers in a high turbidity environment: ² ³ ⁴ Th and ² ¹ ⁰ Pb on the Amazon continental shelf

Joseph M. Smoak, David J. DeMaster, Steven A. Kuehl, Robert H. Pope, more

Geochimica et Cosmochimica Acta > 1996 > 60 > 12 > 2123-2137

Excess ² ³ ⁴ Th and ² ¹ ⁰ Pb seabed inventories were measured in cores collected from the Amazon continental shelf to examine particle scavenging and seabed dynamics. Typical excess ² ¹ ⁰ Pb inventories range from 100 to 300 dpm cm ^- ² , and the total excess ² ¹ ⁰ Pb inventory for the Amazon shelf was determined to be 2.7...

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Phytoplankton biomass and productivity in the Amazon River plume: correlation with seasonal river discharge

Walker O. Smith, David J. Demaster

Continental Shelf Research > 1996 > 16 > 3 > 291-319

Phytoplankton biomass and primary productivity were assessed on the continental shelf in the plume of the Amazon River during a series of cruises conducted within periods of minimum, maximum, rising and falling river discharge. Chlorophyll concentrations were greatest (up to 25.5 μg l⁻¹) in a zone located outside the turbid, high nutrient, low salinity riverine waters but shoreward of the clear, high...

article

Nutrient dynamics in Amazon shelf waters: results from AMASSEDS

David J. Demaster, Robert H. Pope

Continental Shelf Research > 1996 > 16 > 3 > 263-289

Four hydrographic cruises were conducted on the Amazon shelf as part of the AMASSEDS field program. During each cruise, approximately 55 stations were occupied and nutrients, as well as other hydrographic parameters, were measured. The results of this time series sampling program indicate that the nutrient concentrations in the riverine end-member (silicate = 144 μmol kg⁻¹, phosphate = 0.7 μmol kg...

article

Phytoplankton biomass and productivity in the Amazon River plume: correlation with seasonal river discharge

Walker O. Smith, David J. Demaster

Continental Shelf Research > 1996 > 16 > 3 > 291-319

Phytoplankton biomass and primary productivity were assessed on the continental shelf in the plume of the Amazon River during a series of cruises conducted within periods of minimum, maximum, rising and falling river discharge. Chlorophyll concentrations were greatest (up to 25.5 μg l⁻¹) in a zone located outside the turbid, high nutrient, low salinity riverine waters but shoreward of the clear, high...

article

Nutrient dynamics in Amazon shelf waters: results from AMASSEDS

David J. Demaster, Robert H. Pope

Continental Shelf Research > 1996 > 16 > 3 > 263-289

Four hydrographic cruises were conducted on the Amazon shelf as part of the AMASSEDS field program. During each cruise, approximately 55 stations were occupied and nutrients, as well as other hydrographic parameters, were measured. The results of this time series sampling program indicate that the nutrient concentrations in the riverine end-member (silicate = 144 μmol kg⁻¹, phosphate = 0.7 μmol kg...

article

Radionuclide tracers of sediment-water interactions on the Amazon shelf

Willard S. Moore, David J. DeMaster, Joseph M. Smoak, Brent A. McKee, more

Continental Shelf Research > 1996 > 16 > 5-6 > 645-665

A comprehensive study of a variety of radionuclide tracers has been coupled with other geochemical investigations and with sedimentary and physical oceanographic measurements to elucidate processes and their characteristic time scales at the mouth of the Amazon River. This two-year field study on the Amazon continental shelf involved four cruises designed to provide information during different stages...

article

Phytodetritus at the abyssal seafloor across 10° of latitude in the central equatorial Pacific

Craig R. Smith, Daniel J. Hoover, Shawn E. Doan, Robin H. Pope, more

Deep-Sea Research Part II > 1996 > 43 > 4-6 > 1309-1338

Fresh phytoplankton detritus (or phytodetritus) has been reported from numerous deep seafloor sites in the temperate North Atlantic and Pacific Oceans following seasonal phytoplankton blooms. Here we report the first strong evidence for abyssal accumulations of phytodetritus in the tropics, in the central equatorial Pacific. In November-December 1992 we obtained photographs and/or sediment-core...

article

The Amazon shelf setting: tropical, energetic, and influenced by a large river

Charles A. Nittrouer, David J. DeMaster

Continental Shelf Research > 1996 > 16 > 5-6 > 553-573

A Multidisciplinary Amazon Shelf SEDiment Study (AmasSeds) investigated the oceanic processes near the mouth of the Amazon River in order to understand the fate of its enormous discharge of water, solutes and particulates. In addition to receiving a large fluvial discharge, the continental shelf near the Amazon mouth is situated on the equator and experiences an extremely energetic physical regime...

article

Early diagenesis of biogenic opal: Dissolution rates, kinetics, and paleoceanographic implications

James McManus, Douglas E. Hammond, William M. Berelson, Tammy E. Kilgore, more

Deep-Sea Research Part II > 1995 > 42 > 2-3 > 871-903

A study was undertaken to measure the rate of biogenic opal dissolution in equatorial Pacific sediments along the equator between 103 and 140°W, and across the equator between 12°S and 9°N. Along the equator, benthic incubation chamber measurements indicate a gradient in the opal dissolution rate, with rates decreasing from 0.7 mmol m ^- ² day ^- ¹ at 103°W to 0.4 mol m ...

INFONA - science communication portal

Search results for: David J. DeMaster

A seismic study of the Mekong subaqueous delta: Proximal versus distal sediment accumulation

Porewater advection of ammonium into the Neuse River Estuary, North Carolina, USA

Preface and brief synthesis for the FOODBANCS volume

Testing the FOODBANCS hypothesis: Seasonal variations in near-bottom particle flux, bioturbation intensity, and deposit feeding based on 234Th measurements

The FOODBANCS project: Introduction and sinking fluxes of organic carbon, chlorophyll-a and phytodetritus on the western Antarctic Peninsula continental shelf

14C as a tracer of labile organic matter in Antarctic benthic food webs

A synthesis of bentho-pelagic coupling on the Antarctic shelf: Food banks, ecosystem inertia and global climate change

The accumulation and cycling of biogenic silica in the Southern Ocean: revisiting the marine silica budget

Problems and Possible Solutions Concerning Radiocarbon Dating of Surface Marine Sediments, Ross Sea, Antarctica

Latitudinal variations in benthic processes in the abyssal equatorial Pacific: control by biogenic particle flux

The behavior of particle-reactive tracers in a high turbidity environment: ² ³ ⁴ Th and ² ¹ ⁰ Pb on the Amazon continental shelf

Phytoplankton biomass and productivity in the Amazon River plume: correlation with seasonal river discharge

Nutrient dynamics in Amazon shelf waters: results from AMASSEDS

Phytoplankton biomass and productivity in the Amazon River plume: correlation with seasonal river discharge

Nutrient dynamics in Amazon shelf waters: results from AMASSEDS

Radionuclide tracers of sediment-water interactions on the Amazon shelf

Phytodetritus at the abyssal seafloor across 10° of latitude in the central equatorial Pacific

The Amazon shelf setting: tropical, energetic, and influenced by a large river

Early diagenesis of biogenic opal: Dissolution rates, kinetics, and paleoceanographic implications

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