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Title: A time series of benthic flux measurements from Monterey Bay, CA,
Description: In situ incubation chamber measurements of benthic nutrient recycling rates were made on the Monterey Bay shelf at 100m during various years and seasons. Variability in nutrient (Si, PO 4 2+, NH 3, NO 3 -) and trace metal (Mn, Fe (II), Cu) fluxes correlate with variability in the amount of organic carbon oxidized on the sea floor. Patterns of primary productivity show a mid-year maxima, consistent with the timing of increased rates of benthic C org and opal recycling. High rates of C org rain to the shelf promote nitrate consumption at a rate that equals or exceeds ammonia efflux. Low rates of C org rain promote greater efflux of DIN; thus these margin sediments provide a negative feedback to local productivity cycles. The efflux of iron (II) from shelf sediments is sufficient to support > 100% of new production, yet Fe flux is positively correlated with C org recycling which lags the maximum in new production. On account of this time lag, diagenetically recycled Fe is not likely a micro-nutrient trigger of new production, but could serve as a positive feedback. Bio-irrigation rates are seasonally variable by 30% but maximal during the maximum productivity months. © 2003 Elsevier Science Ltd. All rights reserved., Cited By (since 1996):65, CODEN: CSHRD, , , Oceanography
Author: Berelson, McManus, Coale, Johnson, Burdige, Kilgore, Colodner, Chavez, Kudela, Boucher
Date: 2003-01-01T00:00:00Z

Title: A time series of benthic flux measurements from Monterey Bay, CA,
Description: , , , In situ incubation chamber measurements of benthic nutrient recycling rates were made on the Monterey Bay shelf at 100 m during various years and seasons. Variability in nutrient (Si, PO42+, NH3, NO3−) and trace metal (Mn, Fe (II), Cu) fluxes correlate with variability in the amount of organic carbon oxidized on the sea floor. Patterns of primary productivity show a mid-year maxima, consistent with the timing of increased rates of benthic Corg and opal recycling. High rates of Corg rain to the shelf promote nitrate consumption at a rate that equals or exceeds ammonia efflux. Low rates of Corg rain promote greater efflux of DIN; thus these margin sediments provide a negative feedback to local productivity cycles. The efflux of iron (II) from shelf sediments is sufficient to support >100% of new production, yet Fe flux is positively correlated with Corg recycling which lags the maximum in new production. On account of this time lag, diagenetically recycled Fe is not likely a micro-nutrient trigger of new production, but could serve as a positive feedback. Bio-irrigation rates are seasonally variable by 30% but maximal during the maximum productivity months., ,
Author: Berelson, McManus, Coale, Johnson, Burdige, Kilgore, Colodner, Chavez, Kudela, Boucher
Date: 2003-01-01T00:00:00Z

Title: Biogenic matter diagenesis on the sea floor,
Description: Benthic chamber measurements of the reactants and products involved with biogenic matter diagenesis (oxygen, ammonium, nitrate, silicate, phosphate, TCO2, alkalinity) were used to define fluxes of these solutes into and out of the sediments off southern and central California. Onshore to offshore transects indicate many similarities in benthic fluxes between these regions. The pattern of benthic organic carbon oxidation as a function of water depth, combined with published sediment trap records, suggest that the supply of organic carbon from vertical rain can just meet the sedimentary carbon oxidation + burial demand for the central California region between the depths 100-3500 m. However, there is not enough organic carbon raining through the upper water column to support its oxidation and burial in the basins off southern California. Lateral transport and focusing of refractory carbon within these basins is proposed to account for the carbon buried. The organic carbon burial efficiency is greater off southern California (40-60%) compared to central California (2-20%), even though carbon rain rates are comparable. Oxygen uptake rates are not sensitive to bottom water oxygen concentrations nor to the bulk wt. % organic carbon in surficial sediments. Nitrate uptake rates are well defined by the depth of oxygen penetration into the sediments and the overlying water column nitrate concentration. Nitrate uptake accounts for about 50% of the total denitrification taking place in shelf sediments and denitrification (0.1-1.0 mmolN/m2d) occurs throughout the entire study region. The ratio of carbon oxidized to opal dissolved on the sea floor is constant (0.8 ± 0.2) through a wide range of depths, supporting the hypothesis that opal dissolution kinetics may be dominated by a highly reactive phase. Sea floor carbonate dissolution is negligible within the oxygen minimum zone and reaches maximal rates just above and below this zone (0.2-2.0 mmol/m2d)., Cited By (since 1996):72, Oceanography, ,
Author: Berelson, McManus, Coale, Johnson, Kilgore, Burdige, Pilskaln
Date: 1996-01-01T00:00:00Z

Title: Geochemistry of barium in marine sediments,
Description: Variations in the accumulation rate of barium in marine sediments are thought to be indicative of variations in marine biological productivity through time. However, the use of Ba as a proxy for paleoproductivity is partly dependent upon its being preserved in the sediment record in a predictable or consistent fashion. Arguments in favor of high Ba preservation are partly based on the assumption that sediment porewaters are generally at saturation with respect to pure barite. The idea is that because nondetrital sedimentary Ba predominantly exists as barite, porewater saturation would promote burial. We present sediment porewater, sediment solid phase, and benthic incubation chamber data suggesting that solid-phase Ba preservation may be compromised in some geochemical settings. We propose that under suboxic diagenetic conditions, characterized by low bottom water oxygen and high organic carbon respiration rates, Ba preservation may be reduced. Independent of the mechanism, if this assertion is true, then it becomes important to know when the Ba record is unreliable. We present evidence demonstrating that the sedimentary accumulation of authigenic U may serve as a proxy for when the Ba record is unreliable. We then provide an example from the Southern Ocean during the last glacial period where high authigenic U concentrations coincide with high Pa:Th ratios and high accumulation rates of biogenic opal, but we find low accumulation rates of sedimentary Ba. Thus, for the study sites presented here during the last glacial, we conclude that Ba is an unreliable productivity proxy., Cited By (since 1996):163, ,
Author: McManus, Berelson, Klinkhammer, Johnson, Coale, Anderson, Kumar, Burdige, Hammond, Brumsack, McCorkle, Rushdi
Date: 1998-01-01T00:00:00Z

Title: Fluxes of dissolved organic carbon from California continental margin sediments,
Description: Fluxes of dissolved organic carbon (DOC) from marine sediments represent a poorly constrained component of the oceanic carbon cycle that may affect the concentration and composition of DOC in the ocean. Here we report the first in situ measurements of DOC fluxes from continental margin sediments (water depths ranging from 95 to 3,700 m), and compare these fluxes with measured benthic fluxes from 20 other coastal and continental margin sediments. With this combined data set data we have estimated that benthic DOC fluxes are less than ~10% of sediment carbon oxidation rates, and that the integrated DOC flux from sediments in water depths less than 2,000 m is ~180 Tg C/yr. These fluxes are roughly equivalent to the riverine DOC flux, and the organic carbon burial rate in marine sediments. Benthic DOC fluxes therefore represent an important net source of DOC to the oceans. We also note that: (1) benthic DOC fluxes represent a loss of organic carbon from sediments; (2) in many sediments these fluxes appear to be controlled by molecular diffusion (i.e., by pore water concentration gradients); (3) pore water DOC may be an important intermediate in sediment carbon burial and preservation. These observations therefore suggest a linkage between benthic DOC fluxes and sediment carbon preservation that may be mediated by pore water DOC concentrations and cycling. The magnitude and fate of DOC effluxing from marine sediments is thus important to understanding carbon cycles and budgets in the marine environment., Cited By (since 1996):55, ,
Author: Burdige, Berelson, Coale, McManus, Johnson
Date: 1999-01-01T00:00:00Z