Clare E. Reimers

Harnessing microbially generated power on the seafloor

In many marine environments, a voltage gradient exists across the water–sediment interface resulting from sedimentary microbial activity. Here we show that a fuel cell consisting of an anode embedded in marine sediment and a cathode in overlying seawater can use this voltage gradient to generate electrical power in situ. Fuel cells of this design generated sustained power in a boat basin carved into a salt marsh near Tuckerton, New Jersey, and in the Yaquina Bay Estuary near Newport, Oregon. Retrieval and analysis of the Tuckerton fuel cell indicates that power generation results from at least two anode reactions: oxidation of sediment sulfide (a by-product of microbial oxidation of sedimentary organic carbon) and oxidation of sedimentary organic carbon catalyzed by microorganisms colonizing the anode. These results demonstrate in real marine environments a new form of power generation that uses an immense, renewable energy reservoir (sedimentary organic carbon) and has near-immediate application.

Carbon fluxes and burial rates over the continental slope and rise off Central California with implications for the global carbon cycle

The present invention relates to brown cigarette paper having reduced gas phase constituents during pyrolysis wherein the paper which has been stained with humic acid or salts thereof is further treated by washing with water in an amount effective to reduce the amount of water-soluble alkali metal salts present in the paper.

Organic carbon dynamics and preservation in deep-sea sediments

Abstract Three methods of estimating the particulate organic carbon fluxes to the sediment-water interface of the deep Pacific Ocean agree to within the error of the measurements at MANOP sites M, H, and C. Sediment trap experiments, pore water results, and surface sediment organic carbon data suggest that a major fraction of the particulate organic carbon raining to abyssal depths at these locations is degraded within the surface sediments rather than at the sediment-water interface or in the nephloid layer. Organic carbon rain rates at the three sites are similar—within a factor of two; however, the preservation rate of organic carbon and the chemistry of sediment pore waters are very different. A model developed to describe the pore water oxygen and sedimentary carbon distributions indicates model developed to describe the pore water oxygen and sedimentary carbon distributions indicates that changes in the rate constant for organic matter degradation and the bioturbation rate may contribute significantly to the observed differences in character of both pore water and sediment chemistry at these locations. The implication with respect to interpreting the sedimentary record is that cycles of organic carbon and redox sensitive metals (i.e., manganese) are not simply related to particulate organic carbon flux or surface water primary productivity. The residence time of organic carbon with respect to degradation in the surface sediments is on the order of 15 to 150 y.

Dissolution of calcite in deep-sea sediments: pH and O2 microelectrode results

Abstract We present microelectrode profiles of oxygen, pH, and porosity measured at in situ depth across the sediment-water interface from stations above and below the calcite saturation horizon in the equatorial Atlantic. Resistivity electrode data indicate that the diffusion coefficient for solutes is attenuated by nearly a factor of two within the top centimeter of the sediment lattice. Oxygen and porosity data are used to estimate that the organic carbon respiration rate of the sediment is 10–15 μmol cm −2 yr −1 in these locations. Comparison of the pH data with numerical model results reveals that sedimentary calcite dissolves in response to respiration in the top few centimeters of sediment even above the saturation horizon. We calculate that the effective in situ dissolution rate constant for calcite required to explain these data is the neighborhood of 10–100% d −1 . Although more data are needed to confirm this result, it appears to be at least an order of magnitude less than the rate observed in laboratory stirred-reactor experiments.

Benthic foraminiferal population fluctuations related to anoxia: Santa Barbara Basin

The pore-water geochemistry and benthic foraminiferal assemblages of sediments from two slope sites and within the central portion of the Santa Barbara Basin were characterized between February 1988 and July 1989. The highest foraminiferal numerical densities (1197 cm−3 as determined by an ATP assay) occurred at a slope site in June 1988 (550 m) in partially laminated sediments. In continuously laminated sediments from the central basin, foraminifera were found living (as determined by ATP assay) in October 1988 to depths of 4 cm, and specimens prepared for transmission electron microscopy were found with intact organelles to 3 cm, indicating their inhabitation of anoxic pore waters. Ultrastructural data from Nonionella stella is consistent with the hypothesis that this species can survive by anaerobic respiration. However, the benthic foraminifera appear unable to survive prolonged anoxia. The benthic foraminiferal population was completely dead in July 1989 when bottom water O2 was undetectable.

Benthic chamber and profiling landers in oceanography - A review of design, technical solutions and functioning

We review and evaluate the design and operation of twenty-seven known autonomous benthic chamber and profiling lander instruments. We have made a detailed comparison of the different existing lander designs and discuss the relative strengths and weaknesses of each. Every aspect of a lander deployment, from preparation and launch to recovery and sample treatment is presented and compared. It is our intention that this publication will make it easier for future lander builders to choose a design suitable for their needs and to avoid unnecessary mistakes.

Porewater pH and authigenic phases formed in the uppermost sediments of the Santa Barbara Basin

Abstract In this paper porewater and solid phase analyses are used in combination with in situ O 2 and pH microelectrode measurements to characterize early diagenetic processes in the uppermost sediments of the Santa Barbara Basin, California. Rapid reduction of dissolved oxygen, nitrate, solid phase manganese and iron, and dissolved sulfate is observed. Between sediment depths of 0 and 2 cm, reductive solubilization of ferric iron phases releases Fe 2+ , adsorbed phosphate, and fluoride to the porewaters and contributes to a sharp increase in porewater pH. Between 2 and 4 cm, sulfate reduction rates peak, pH levels off, and acid volatile sulfides and pyrite become the dominant forms of solid phase iron. Saturation state calculations, which depend largely on pH, indicate that the porewaters of the Santa Barbara Basin become saturated with respect to carbonate fluorapatite and calcite within the first 0.25 mm of the sediment and are highly supersaturated by and below 2 cm. In spite of this result, porewater evidence of phosphate and fluoride removal into a solid phase is observed only in the first ∼5 cm of some cores, whereas dissolved Ca profiles suggest dispersed calcite precipitation throughout the sediment column. This finding is interpreted as an indication of the nonsteady state nature of the surface reactions that may, given sufficient nucleation sites and time, lead to carbonate fluorapatite genesis in anoxic sediments. Finally, microelectrode pH profiles from two other basins in the California Borderlands are presented. These demonstrate that the porewaters of the Santa Barbara Basin are more alkaline than those of other basins. This outcome is attributed to the lack of particle mixing and a unique interplay between Fe liberation and FeS precipitation reactions in the Santa Barbara Basin.

GRAIN SHAPE EFFECTS ON SETTLING RATES

The departure of a grain from a spherical shape causes a decrease in its settling velocity within a fluid. The more non-spherical the particle the greater the departure from the settling velocity of a spherical grain of the same weight. This study reexamines the various measures of sphericity and their ability to predict the drag coefficient and settling velocity of a non-spherical grain. Experiments were conducted using ellipsoidal pebbles settling in glycerine which has a viscosity some 1,000 times greater than water. The Reynolds numbers range from 0.07-1.5 which is the same range as quartz-density coarse silt through very fine sand settling in water. Therefore the results of the experiments are applicable to common sedimentary materials. The use of pebbles allows for the better determinations of the shape parameters, and eliminates the effects of grain surface roughness and roundness and grain asymmetries that complicate the settling of silt and sand. Analysis of the pebble-settling data indicates that the Corey shape factor provides a much better prediction of the drag coefficient for non-spherical grains than does the sphericity definition of Wadell which is based on the ratio of the surface area of a sphere with the same weight as the pebble to the actual surface area of the pebble. Regression of the data provides an equation which predicts the drag coefficient of the settling particle from its Corey shape factor and the Reynolds number. This drag coefficient relationship is used to obtain a modification of the familiar Stokes settling velocity equation which accounts for non-spherical grain shape effects on the settling rate. The results based on the pebble data are extended to Reynolds numbers up to

The partitioning of organic carbon fluxes and sedimentary organic matter decomposition rates in the ocean

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