Microbial Diversity in Nankai Trough Sediments at a Depth of 3,843 m

Dense populations of bivalves, primarily Calyptogena sp., were observed at cold seeps of the Nankai Trough. Bacterial input to the sediment was estimated through determination of phospholipid ester-linked fatty acid (PLFA) and DNA profiles. Results indicated a bacterial biomass of 10⁹ cells (g dry wt)^-1 while individual fatty acid profiles revealed a predominance of monounsaturated fatty acids, mainly 18:1 isomers. The presence of these fatty acids can be interpreted to reflect a response to low temperature and a predominance of psychrophilic bacteria. DNA fragments encoding bacterial ribosomal RNA small-subunit sequences (16S rDNA) were amplified by the polymerase chain reaction method using DNA extracted directly from the sediment samples. From the sequencing results, at least 19 kinds of bacterial 16S rDNAs related to mostly the Proteobacteria and a few gram-positive bacteria were identified. These results suggest that the bacterial community in the Nankai Trough sediments consists of mainly bacteria belonging to the Proteobacteria , , and subdivisions. Bacteria belonging to the and subdivisions, which are known to include epibiont and sulfate reducing bacteria, respectively, were mostly detected in the sediment obtained from inside the area of the Calyptogena community, and the -Proteobacteria may function to supply reduced sulfur to bacterial endosymbionts of Calyptogena.     

Water quality impacts from mining in the Black Hills,South Dakota,USA

The focus of this research was to determine if abandoned mines constitute a major environmental hazard in the Black Hills. Many abandoned gold mines in the Black Hills contribute acid and heavy metals to streams. In some areas of sulfide mineralization local impacts are severe, but in most areas the impacts are small because most ore deposits consist of small quartz veins with few sulfides. Pegmatite mines appear to have negligible effects on water due to the insoluble nature of pegmatite minerals. Uranium mines in the southern Black Hills contribute some radioactivity to surface water, but the impact is limited because of the dry climate and lack of runoff in that area.     

Effects of hopper dredging and sediment dispersion,chesapeake bay

Hopper dredging operations release suspended sediment into the environment by agitation of the bed and by discharge of overflow slurries. Monitoring of turbidity and suspended sediment concentrations in central Chesapeake Bay revealed two plumes: (1) an upper plume produced by overflow discharge and (2) a near-bottom plume produced by draghead agitation and rapid settling from the upper plume. The upper plume dispersed over 5.7 km² extending 5,200 meters form the discharge point. Redeposited sediment accumulated on channel flanks covering an area of 6.4 km² and reached a thickness of 19 cm. Altogether dredging redistributed into the environment an estimated 100,000 tons of sediment or 12 percent of the total material removed.Near-field concentrations of suspended sediment, less than 300 m from the dredge, reach 840 to 7,200 mg/L or 50 to 400 times the normal background level. Far-field concentrations (>300 m) are enriched 5 to 8 times background concentrations and persist 34 to 50 percent of the time during a dredging cycle (1.5 to 2.0 h). The overflow discharge plume evolves through three dispersion phases: (1) convective descent, (2) dynamic collapse, and (3) long-term passive diffusion (Clark and others 1971). The bulk of the material descends rapidly to the bottom during the convective descent phase, whereas the cloud that remains in suspension is dispersed partly by internal waves. Although suspended sediment concentrations in the water column exceed certain water quality standards, benthic communities survived the perturbation with little effect.     

Internally consistent gahnitic spinel-cordierite-garnet equilibria in the FMASHZn system: geothermobarometry and applications

The equilibrium (Mg, Fe, Zn)₃Al₂Si₃O₁₂+2Al₂SiO₅=3(Mg, Fe, Zn)Al₂O₄+5SiO₂ garnet + sillimanite/kyanitc = spinel + quartz was calibrated in the piston-cylinder apparatus between 11 and 30 kbar, and over the temperature range of 950 to 1200°C. Three experimental mixes of Mg no. [100^*MgO/(MgO+FeO)] 40, 47 and 60, in the FeO –MgO–Al₂O₃–SiO₂–ZnO (FMASZn) system were used under low oxygen fugacities and anhydrous conditions. We derive a ternary Fe–Mg–Zn symmetric mixing model for aluminous spinels in equilibrium with garnet, to quantify the increase in gahnitic end-member of spinel with increasing pressure and descreasing temperature. Further experiments in the spinel-cordieritequartz-sillimanite field were combined with garnet-cordierite data from the literature to produce a consistent set of equations describing the exchange reactions in FMASHZn relevant to quartz-sillimanite bearing rocks at granulite facies conditions. As spinel is an important mineral participating in many rocks of aluminous composition at granulite-facies conditions, and as zinc contributes to an enlargement of spinel's stability field towards higher pressures and lower temperatures, the thermobarometric calibrations presented here will be most significant in delineating the prograde and retrograde trajectory of P-T paths.     

Vadose zone-attenuated artificial recharge for input to a ground water model

Accurate representation of artificial recharge is requisite to calibration of a ground water model of an unconfined aquifer for a semiarid or arid site with a vadose zone that imparts significant attenuation of liquid transmission and substantial anthropogenic liquid discharges. Under such circumstances, artificial recharge occurs in response to liquid disposal to the vadose zone in areas that are small relative to the ground water model domain. Natural recharge, in contrast, is spatially variable and occurs over the entire upper boundary of a typical unconfined ground water model. An improved technique for partitioning artificial recharge from simulated total recharge for inclusion in a ground water model is presented. The improved technique is applied using data from the semiarid Hanford Site. From 1944 until the late 1980s, when Hanford's mission was the production of nuclear materials, the quantities of liquid discharged from production facilities to the ground vastly exceeded natural recharge. Nearly all hydraulic head data available for use in calibrating a ground water model at this site were collected during this period or later, when the aquifer was under the diminishing influence of the massive water disposals. The vadose zone is typically 80 to 90 m thick at the Central Plateau where most production facilities were located at this semiarid site, and its attenuation of liquid transmission to the aquifer can be significant. The new technique is shown to improve the representation of artificial recharge and thereby contribute to improvement in the calibration of a site-wide ground water model.     

Habitat selection and quality for multiple cohorts of young-of-the-year bluefish (Pomatomus saltatrix): Comparisons between estuarine and ocean beaches in southern New Jersey

In this study, seasonal and annual variability in the use of estuarine and ocean beaches by young-of-the-year bluefish, Pomatomus saltatrix, was evaluated by indices of abundance in coastal areas of southern New Jersey (1998–2000). Biological and physical factors measured at specific sites were correlated with bluefish abundance to determine the mechanisms underlying habitat selection. In addition, integrative and discrete indicators of bluefish growth were used to examine spatio-temporal dynamics in habitat quality and its effect on habitat selection by multiple cohorts of bluefish. Intra-annual recruitment to coastal areas of southern New Jersey was episodic, and resulted from the ingress of spring-spawned bluefish (hatch-date April) to estuarine beaches in late May to early June, followed by the recruitment of summer-spawned fish (hatch-date early July) to ocean beaches from July to October. Bluefish utilized estuarine and ocean beaches in a facultative manner that was responsive to dynamics in prey composition and temperature conditions. The recruitment and residency of bluefish in the estuary (1998–1999) and ocean beaches (1998), for example, was coincidental with the presence of the Atlantic silverside Menidia menidia and bay anchovy Anchoa mitchilli, the principal prey species for bluefish occupying these respective habitat-types. Bluefish abundance in the estuary (2000) and ocean beaches (1999–2000) was also correlated with water temperature, with the greatest catches of juveniles coinciding with their optimal growth temperature (24 °C). Bluefish growth, estimated as the slope of age–length relationships and daily specific growth rates, equaled 1.27–2.63 mm fork length (FL) d⁻¹ and 3.8–8.7% body length increase d⁻¹, respectively. The growth of sagittal otoliths was also used as a proxy for changes in bluefish size during and shortly before their time of capture. Accordingly, otolith growth rates of summer-spawned bluefish were greater at ocean beaches relative to the estuary and were explained by the more suitable temperature conditions found at ocean beaches during the mid- to late summer. Notwithstanding the fast growth of oceanic summer-spawned bluefish, individuals spawned in the spring were still larger in absolute body size at the end of the summer growing season (240 and 50–200 mm FL for spring- and summer-spawned bluefish, respectively). The size discrepancy between spring- and summer-spawned bluefish at the onset of autumn migrations and during overwintering periods may account for the differential recruitment success of the respective cohorts.     

Trapping of noble gases in proton-irradiated silicate smokes

Abstract— We have measured Ne, Ar, Kr and Xe in Si₂O₃ “smokes” that were condensed on Al substrates, vapor-deposited with various mixtures of CH₄, NH₃, H₂O and noble gases at 10 K and subsequently irradiated with 1 MeV protons to simulate conditions during grain mantle formation in interstellar clouds. The noble gases were analyzed using conventional stepwise heating and static noble gas mass spectrometry. Neither Ne nor Ar is retained by the samples upon warming to room temperature, but Xe is very efficiently trapped and retained. Kr is somewhat less effectively retained, typically depleted by factors of about 10–20 relative to Xe. Isotopic fractionation favoring the heavy isotopes of Xe and Kr of about 5–10‰/amu is observed. Correlations between the specific chemistry of the vapor deposition and heavy noble gas retention are most likely the result of competition by the various species for irradiation-produced trapping sites. The concentration of Xe retained by some of these smokes exceeds that observed in phase Q of meteorites and, like phase Q, they do not seem to be carriers of the light noble gases. Such artificially prepared material may, therefore, offer clues concerning the incorporation of the heavy planetary noble gases in meteoritic material and the nature of phase Q.