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At least 451 records · Page 25Linked to original sources

USGS2023

Hydrothermal monazite and xenotime chemistry as genetic discriminators for intrusion-related and orogenic gold deposits: Implications for an orogenic origin of the Pogo gold deposit, Alaska

Attempts to geochemically distinguish between metamorphic-hydrothermal systems that form orogenic gold deposits and both reduced and oxidized magmatic-hydrothermal systems using isotopes or metal associations have proven ambiguous, particularly for orogenic gold and reduced intrusion-related gold systems. The absence of conclusive geochemical discriminators and the overlap in geologic characteristics have led to gold deposit models being potentially incorrectly applied, which in turn negatively affect regional mineral exploration and mine planning. In this study, in situ electron microprobe geochemical analyses of hydrothermal monazite and xenotime crystals associated with different types of gold-bearing deposits are shown to be effective geochemical discriminators. There are notable differences in mineral chemistry such as rare earth element (REE) profiles, total light REE, Dy, Er, Pr, Y, Nd/Sm, and La/Sm that distinguish monazite precipitated from metamorphic-hydrothermal fluids that form orogenic gold deposits and those precipitated from magmatic-hydrothermal fluids that form both porphyry Cu-Mo-Au and reduced intrusion-related gold deposits. Notable differences in overall xenotime abundances and concentrations of heavy REEs, Ca, and Sc are distinctive between the different deposit classes for xenotime. The origin of the controversially classified Pogo gold deposit, Tintina gold province, Alaska, which has been characterized as both a reduced intrusion-related and an orogenic gold deposit, is tested based upon the noted chemical differences associated with these hydrothermal phosphates. The findings of this study have implications for exploration and mine development in the Tintina gold province and other areas that contain deposits that are controversially classified as either orogenic or as magmatic-hydrothermal gold deposits.

Alaska↗

USGS2026

Microtextural characteristics of adularia in banded quartz veins from the Midas low-sulfidation epithermal deposit, Nevada

High-grade ores at the Miocene Midas low-sulfidation epithermal deposit in northern Nevada are confined to crustiform quartz veins containing abundant adularia. Micro-X-ray fluorescence elemental mapping reveals that adularia is a common gangue mineral occurring in colloform bands, bands showing bladed textures, and bands with dendritic terminations. The adularia aggregates have delicate shapes and are comprised of stacked, submillimeter crystals hosted by fine-grained quartz. The textural evidence suggests that the adularia aggregates originally formed within a gel-like, noncrystalline silica matrix, which subsequently transformed into quartz. This indicates that the adularia did not precipitate in open space along the vein walls. Correlative microscopy, involving scanning electron microscopy-based automated mineralogy and optical petrography, demonstrates that bands containing abundant adularia are not the primary host to ore minerals. The ore minerals occur in different bands within the crustiform veins, implying that adularia and ore mineral precipitation did not always occur simultaneously. It is hypothesized here that fluid flow at Midas involved intermittent short-lived events of fluid flashing, causing rapid solute supersaturation in the liquid. During each flashing event, different amounts of vapor were produced along a given vein. Compositional differences between adjacent bands in the crustiform quartz veins may, therefore, be linked to variations in the amount of vapor formed during each flash event.

Nevada↗

USGS2002

Organochlorine chemical residues in fish from the Mississippi River basin, 1995

Fish were collected in late 1995 from 34 National Contaminant Biomonitoring Program (NCBP) stations and 13 National Water Quality Assessment Program (NAWQA) stations in the Mississippi River basin (MRB) and in late 1996 from a reference site in West Virginia. Four composite samples, each comprising (nominally) 10 adult common carp (Cyprinus carpio) or black bass (Micropterus spp.) of the same sex, were collected from each site and analyzed for organochlorine chemical residues by gas chromatography with electron capture detection. At the NCBP stations, which are located on relatively large rivers, concentrations of organochlorine chemical residues were generally lower than when last sampled in the mid-1980s. Residues derived from DDT (primarily p,p???-DDE) were detected at all sites (including the reference site); however, only traces (??? 0.02 ??g/g) of the parent insecticide (p,p???-DDT) were present, which indicates continued weathering of residual DDT from past use. Nevertheless, concentrations of DDT (as p,p???-DDE) in fish from the cotton-farming regions of the lower MRB were great enough to constitute a hazard to fish-eating wildlife and were especially high at the NAWQA sites on the lower-order rivers and streams of the Mississippi embayment. Mirex was detected at only two sites, both in Louisiana, and toxaphene was found exclusively in the lower MRB. Most cyclodiene pesticides (dieldrin, chlordane, and heptachlor epoxide) were more widespread in their distributions, but concentrations were lower than in the 1980s except at a site on the Mississippi River near Memphis, TN. Concentrations were also somewhat elevated at sites in the Corn Belt. Endrin was detected exclusively at the Memphis site. PCB concentrations generally declined, and residues were detected (??? 0.05 ??g/g) at only 35% of the stations, mostly in the more industrialized parts of the MRB.

Archives of Environmental Contamination and Toxico↗

USGS2005

Residues of toxaphene in insectivorous birds ( Petrochelidon spp.) from the Rio Grande, Texas

Although it has been documented that wildlife in the Rio Grande Valley (RGV) contain increased concentrations of organochlorine (OC) contaminants, particularly DDE, little has been published on residues of toxaphene throughout this major North American watershed. In this study, 28 liver composites from adult swallows ( Petrochelidon spp.) collected along the Rio Grande from 1999 through 2000 were analyzed for toxaphene residues using congener-specific gas chromatography–electron-capture negative ionization–mass spectrometry. Estimated total toxaphene concentrations ranged from 12 to 260 ng/g wet wt and were highest in samples from the lower RGV near Llano Grande Lake in Hidalgo and Cameron counties (Texas). Toxaphene congener profiles were relatively invariant throughout the watershed and were dominated by 2,2,5-endo,6-exo,8,8,9,10-octachlorobornane (P-42a or B8-806) with lesser amounts of several other Cl 7 -Cl 9 compounds, many of which remain unidentified. Petrochelidon spp. liver profiles appear to be intermediate in complexity between those in invertebrates and fish (more complex) and mammals (less complex) and differs somewhat from those reported for other avian species. In addition to other legacy OC contaminants, toxaphene residues were most concentrated in the lower RGV and accumulated at up to hundreds of parts per billion in these insect-eating birds, underscoring their utility as avian bioindicators of persistent organic pollutants.

Archives of Environmental Contamination and Toxico↗

USGS1996

Comparison of gas chromatography/mass spectrometry and immunoassay techniques on concentrations of atrazine in storm runoff

Gas chromatography/mass spectrometry (GC/MS) and enzyme-linked immunosorbent assay (ELISA) techniques were used to measure concentrations of dissolved atrazine in 149 surface-water samples. Samples were collected during May 1992–September 1993 near the mouth of the White River (Indiana) and in two small tributaries of the river. GC/MS was performed on a Hewlett-Packard 5971 A, with electron impact ionization and selected ion monitoring of filtered water samples extracted by C-18 solid phase extraction; ELISA was performed with a magnetic-particle-based assay with photometric analysis. ELISA results compared reasonably well to GC/MS measurements at concentrations below the Maximum Contaminant Level for drinking water set by the U.S. Environmental Protection Agency (3.0 μg/L), but a systematic negative bias was observed at higher concentrations. When higher concentration samples were diluted into the linear range of calibration, the relation improved. A slight positive bias was seen in all of the ELISA data compared to the GC/MS results, and the bias could be partially explained by correcting the ELISA data for cross reactivity with other triazine herbicides. The highest concentrations of atrazine were found during the first major runoff event after the atrazine was applied. Concentrations decreased throughout the rest of the sampling period even though large runoff events occurred during this time, indicating that most atrazine loading to surface waters in the study area occurs within a few weeks after application. Use of brand names is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey, the Uniroyal Chemical Company, or Wichita State University.

Indiana↗

USGS2017

Use of fish telemetry in rehabilitation planning, management, and monitoring in Areas of Concern in the Laurentian Great Lakes

Freshwater ecosystems provide many ecosystem services; however, they are often degraded as a result of human activity. To address ecosystem degradation in the Laurentian Great Lakes, Canada and the United States of America established the Great Lakes Water Quality Agreement (GLWQA). In 1987, 43 highly polluted and impacted areas were identified under the GLWQA as having one or more of 14 Beneficial Use Impairments (BUIs) to the physical and chemical habitat for fish, wildlife and humans, and were designated as Areas of Concern (AOC). Subnational jurisdictions combined with local stakeholders, with support from federal governments, developed plans to remediate and restore these sites. Biotelemetry (the tracking of animals using electronic tags) provides information on the spatial ecology of fish in the wild relevant to habitat management and stock assessment. Here, seven case studies are presented where biotelemetry data were directly incorporated within the AOC Remedial Action Plan (RAP) process. Specific applications include determining seasonal fish–habitat associations to inform habitat restoration plans, identifying the distribution of pollutant-indicator species to identify exposure risk to contamination sources, informing the development of fish passage facilities to enable fish to access fragmented upstream habitats, and assessing fish use of created or restored habitats. With growing capacity for fish biotelemetry research in the Great Lakes, we discuss the strengths and weaknesses of incorporating biotelemetry into AOC RAP processes to improve the science and practice of restoration and to facilitate the delisting of AOCs.

Great Lakes↗

USGS2006

Magnesium content within the skeletal architecture of the coral Montastraea faveolata : locations of brucite precipitation and implications to fine-scale data fluctuations

Small portions of coral cores were analyzed using a high-resolution laser ablation inductively coupled plasma mass spectrometer (LA ICP-MS) to determine the geochemical signatures within and among specific skeletal structures in the large framework coral, Montastraea faveolata . Vertical transects were sampled along three parallel skeletal structures: endothecal (septal flank), corallite wall, and exothecal (costal flank) areas. The results demonstrate that trace element levels varied among the three structures. Magnesium (Mg) varied among adjacent structures and was most abundant within the exothecal portion of the skeleton. Scanning electron microscopy (SEM) revealed the presence of hexagonal crystals forming thick discs, pairs or doublets of individual crystals, and rosettes in several samples. High Mg within these crystals was confirmed with energy dispersive spectroscopy (EDS), infrared spectrometry, and LA ICP-MS. The chemical composition is consistent with the mineral brucite [Mg(OH 2 )]. These crystals are located exclusively in the exothecal area of the skeleton, are often associated with green endolithic algae, and are commonly associated with increased Mg levels found in the adjacent corallite walls. Although scattered throughout the exothecal, the brucite crystals are concentrated within green bands where levels of Mg increase substantially relative to other portions of the skeleton. The presence and locations of high-Mg crystals may explain the fine-scale fluctuations in Mg data researchers have been questioning for years.

Florida↗

USGS2024

Pathology of lesions in corals from the US Virgin Islands after emergence of stony coral tissue loss disease

Stony coral tissue loss disease (SCTLD) was first documented in Florida in 2014 and has since spread through the Caribbean causing unprecedented mortality in more than 20 species of corals. The cause of SCTLD is unknown, but bacteria are suspected based on regression of gross lesions in some corals treated with antibiotics. Limited pathology studies on SCTLD exist, but it is likely that ‘SCTLD’ is a general term encompassing tissue loss disease of unexplained origin. Here, we examined pathology of lesions in corals from the US Virgin Islands where SCTLD has recently emerged. The typical histologic lesion of SCTLD in Florida corals was lytic necrosis comprising vacuolation and necrosis of mucus cells with erosion of mesoglea and misshapen endosymbionts with variably sized intracytoplasmic granules and common occurrence of filamentous viral-like particles in endosymbionts visible on electron microscopy (EM). In contrast, USVI corals had mainly lytic mucus cell hypertrophy and necrosis with no involvement of mesoglea, endosymbiont pathology at the light microscopy level was less evident, and VLP were rarely seen on EM. We suspect SCTLD is likely more complex with multiple presentations and potential etiologies depending on geographic region. Further pathological studies from other regions might help refine the case definition of SCTLD.

St. John↗

USGS2017

Morphological and molecular characterization of Sarcocystis arctica-like sarcocysts from the Arctic fox (Vulpes lagopus) from Alaska, USA

The muscles of herbivores commonly harbor sarcocysts of parasites belonging to species in the genus Sarcocystis, but such muscle parasites are rare in carnivores. Here, we report Sarcocystis arctica -like sarcocysts in muscles of Arctic foxes ( Vulpes lagopus ) from Alaska, USA, for the first time. The tongues of 56 foxes were examined for Sarcocystis infection using several methods. Sarcocystis bradyzoites were detected in pepsin digests of 13 (23.2%), and sarcocysts were found in histological sections stained with hematoxylin and eosin (HE) of 9 (16.0%). By light microscopy, sarcocysts were up to 4 mm long and up to 245 μm wide. In HE-stained sections, the sarcocyst wall appeared smooth and up to 1.5 μm thick without visible protrusions. By transmission electron microscopy, the sarcocyst wall had a wavy parasitophorous vacuolar membrane (pvm) folded as pleomorphic villar protrusions (vp), sometimes with anastomoses of villar tips. The vp and the ground substance (gs) layer were smooth and without microtubules. The gs was up to 2.0 μm thick. The total width of the wall including vp and the gs was up to 4.0 μm. The vp were up to 3.0 μm long and most closely resembled “type 9c.” All sarcocysts were mature and contained numerous 8.1 × 2.1 μm sized bradyzoites. Molecular characterization (at 18S rDNA , 28S rDNA, ITS-1, and cox1) showed the highest affinity for S. arctica of the Arctic fox ( V. lagopus ) from Norway. In the present investigation, we provide evidence that sarcocysts are common in tongues of Alaskan Arctic foxes suggesting that these carnivores are serving as intermediate hosts, and we also provide ultrastructure of S. arctica from the Arctic fox for the first time.

Alaska↗

USGS2012

Degassing of Cl, F, Li and Be during extrusion and crystallization of the rhyolite dome at Volcán Chaitén, Chile during 2008 and 2009

We investigated the distribution of Cl, F, Li, and Be in pumices, obsidians, and crystallized dome rocks at Chaitén volcano in 2008–2009 in order to explore the behavior of these elements during explosive and effusive volcanic activity. Electron and ion microprobe analyses of matrix and inclusion glasses from pumice, obsidian, and microlite-rich dome rock indicate that Cl and other elements were lost primarily during crystallization of the rhyolitic dome after it had approached the surface. Glass in pumice and microlite-free obsidian has 888 ± 121 ppm Cl, whereas residual glass in evolved microlite-rich dome rock generally retains less Cl (as low as <100 ppm). Estimated Cl losses were likely >0.7 Mt Cl, with a potential maximum of 1.8 Mt for the entire 0.8-km 3 dome. Elemental variations reflect an integrated bulk distribution ratio for Cl > 1.7 (1.7 times more Cl was degassed or incorporated into crystals than remained in the melt). Because Cl is lost dominantly as the very last H 2 O is degassed, and Cl is minimally (if at all) partitioned into microlites, the integrated vapor/melt distribution ratio for Cl exceeds 200 (200 times more Cl in the evolved vapor than in the melt). Cl is likely lost as HCl, which is readily partitioned into magmatic vapor at low pressure. Cl loss is accelerated by the change in the composition of the residual melt due to microlite growth. Cl loss also may be affected by open-system gas fluxing. Integrated vapor-melt distribution ratios for Li, F, and Be all exceed 1,000. On degassing, an unknown fraction of these volatiles could be immediately dissolved in rainwater.

Volcï¿½n Chaitï¿½n↗

USGS2021

A petrological and conceptual model of Mayon volcano (Philippines) as an example of an open-vent volcano

Mayon is a basaltic andesitic, open-vent volcano characterized by persistent passive degassing from the summit at 2463 m above sea level. Mid-size (<0.1 km3) and mildly explosive eruptions and occasional phreatic eruptions have occurred approximately every 10 years for over a hundred years. Mayon’s plumbing system structure, processes, and time scales driving its eruptions are still not well-known, despite being the most active volcano in the Philippines. We investigated the petrology and geochemistry of its crystal-rich lavas (~50 vol% phenocrysts) from nine historical eruptions between 1928 and 2009 and propose a conceptual model of the processes and magmatic architecture that led to the eruptions. The whole-rock geochemistry and mineral assemblage (plagioclase + orthopyroxene + clinopyroxene + Fe-Ti oxide ± olivine) of the lavas have remained remarkably homogenous (54 wt% SiO2,~4 wt% MgO) from 1928 to 2009. However, electron microscope images and microprobe analyses of the phenocrysts and the existence of three types of glomerocrysts testify to a range of magmatic processes, including long-term magma residence, magma mixing, crystallization, volatile fluxing, and degassing. Multiple mineral-melt geothermobarometers suggest a relatively thermally buffered system at 1050±25 °C, with several magma residence zones, ranging from close to the surface, through reservoirs at ~4–5 km, and as deep as ~ 20 km. Diffusion chronometry on >200 orthopyroxene crystals reveal magma mixing timescales that range from a few days to about 65 years, but the majority are shorter than the decadal inter-eruptive repose period. This implies that magma intrusion at Mayon has been nearly continuous over the studied time period, with limited crystal recycling from one eruption to the next. The variety of plagioclase textures and zoning patterns reflect fluxing of volatiles from depth to shallower melts through which they eventually reach the atmosphere through an open conduit. The crystal-rich nature of the erupted magmas may have developed during each inter-eruptive period. We propose that Mayon has behaved over almost 100 years as a steady state system, with limited variations in eruption frequency, degassing flux, magma composition, and crystal content that are mainly determined by the amount and composition of deep magma and volatile input in the system. We explore how Mayon volcano’s processes and working model can be related to other open-vent mafic and water-rich systems such as Etna, Stromboli, Villarrica, or Llaima. Finally, our understanding of open-vent, persistently active volcanoes is rooted in historical observations, but volcano behavior can evolve over longer time frames. We speculate that these volcanoes produce specific plagioclase textures that can be used to identify similar volcanic behavior in the geologic record.

Mayon volcano↗

USGS2021

Evolution in eruptive style of the 2018 eruption of Veniaminof volcano, Alaska, reflected in groundmass textures and remote sensing

Variable eruptive style and explosivity is common in basaltic to basaltic andesite volcanoes but can have uncertain origins. Veniaminof volcano in the Alaska-Aleutian arc is a frequently active open-vent center, regularly producing Strombolian eruptions and small lava flows from an intracaldera cone within an intracaldera ice cap. The September–December 2018 eruption of Veniaminof evolved in explosivity over time. The eruption was documented with frequent satellite observations, syn- and post-eruption structure-from-motion photo surveys, and post-eruption sampling of lava flows and tephra preserved in the syn-eruption snowpack. Lava flows with a total volume of ~ 6 × 10 6 m 3 flowed down the cone flanks into the ice cap, overthickening at ice marginal flow fronts. Smaller tephra deposits were estimated at ~ 1–2 × 10 6 m 3 dense rock equivalent, with almost half of this volume deposited directly on the eruptive cone itself. Erupted products were basaltic andesite, and composition (54 ± 0.7 wt% bulk rock, 58 ± 0.7 wt% glass SiO 2 ), sideromelane microlite crystallinity (20–30%), and microlite number density (plagioclase 6.4 ± 2.6 × 10 5 n/mm 3 ) did not change significantly over the eruption suggesting a similar magma source and ascent rate. We defined tephra componentry with groundmass microcrystalline textures using backscatter electron images. The componentry of tephra groundmass showed significant increases in tachylite grains, defined here by the presence of dendritic interstitial nanolites, corresponding to increasing seismic tremor and periods of increased ash emissions. We suggest that these componentry changes reflect increasing undercooled zones on the conduit margins that increased brittle shearing, fragmentation, and ultimately ash emissions.

Alaska↗

USGS2025

Fluid inclusion constraints on the geometry of the magmatic plumbing system beneath Mauna Loa – Part I: Lavas and tephras

There are few petrological constraints on magma storage depths at Mauna Loa, Hawai‘i. Yet understanding the geometry of the magmatic plumbing system is critical for interpreting geophysical signals of unrest at this very high-threat volcano. We address this gap by examining CO₂-rich fluid inclusions (FI) in lava and tephra from seven eruptions (8870 ± 56 14C yr BP, 1852, 1855, 1868, 1949, 1950, and 1984), supplemented with published data from 2022. Raman spectroscopy was used to determine FI densities, from which entrapment pressures were calculated using a CO₂-H₂O equation of state. Most FI record pressures of ~ 0.25–1.25 kbar (~ 2–5 km depth below the summit), consistent with geophysical estimates from the past 40 years. In summit eruptions, FI hosted in more evolved olivine and orthopyroxene clots (Fo and Mg# < 84) record slightly shallower pressures than those in more primitive olivines (Fo > 84) from rift zone eruptions, suggesting a crystal-poor evolved cap near the top of the reservoir (~ 2 km). The similarity in storage depths across all eight eruptions indicates that Mauna Loa’s magmas have tapped a quasi-stable reservoir over the past two centuries, and possibly over 10 kyr. Electron backscatter diffraction reveals deformations to the crystal lattice in Fo82-83 olivines, likely due to deformation during storage in mush piles. The intensity of deformation is comparable to that seen at Kīlauea, implying that mush pile stress may be decoupled from edifice size or longevity. Finally, SO₂ contents in FI increase from ~ 2 mol% at 2 kbar to ~ 15 mol% at 0.5 kbar, suggesting sulphur degassing begins far deeper than the 0.2–0.3 kbar commonly assumed for Hawaiian systems. This validates the newest generation of S degassing models (e.g., Sulfur_X), and explains precursory SO2 emissions in the ~3 hours prior to the onset of the 2022 eruption (Esse et al. 2025).

Hawaii↗

USGS2024

Real-time invasive sea lamprey detection using machine learning classifier models on embedded systems

Invasive sea lamprey ( Petromyzon marinus ) has historically inflicted considerable economic and ecological damage in the Great Lakes and continues to be a major threat. Accurately monitoring sea lampreys are critical to enabling the deployment of more targeted and effective control measures to minimize the impact associated with this species. This paper presents the first stand-alone system for real-time detection of sea lamprey attachment on underwater surfaces through the use of classifier models deployed on a microcontroller system. A range of low-complexity models was explored: single-layer artificial neural networks, logistic regression, Gaussian Naive-Bayes, decision trees, random forest, and Scalable, Efficient, and Fast classifieR (SEFR). Threshold models tuned using a multi-objective optimization formulation were also considered. Classifier models were trained with a dataset generated through live animal testing and presented accuracies between 80 and 86%. The models were deployed on an Arduino microcontroller platform and compared in classification accuracy, detection performance, time complexity, and memory size using real-time detection testing. Classification accuracies between 65 and 75% were observed during validation. Models demonstrated good capture rates for lamprey attachments (63–85%), and average detection delays ranging from 9 to 36 s. A video demonstrating the operation of the system during a real-time validation test is also included in this work. While there is room for improving the accuracy of the system, this research presents the first step toward an electronic sea lamprey monitoring system that can provide a detailed view of sea lamprey activity enhancing control and conservation efforts across its entire range.

Neural Computing and Applications↗

USGS2009

Enrichment and isolation of Bacillus beveridgei sp. nov., a facultative anaerobic haloalkaliphile from Mono Lake, California, that respires oxyanions of tellurium, selenium, and arsenic

Mono Lake sediment slurries incubated with lactate and tellurite [Te(IV)] turned progressively black with time because of the precipitation of elemental tellurium [Te(0)]. An enrichment culture was established from these slurries that demonstrated Te(IV)-dependent growth. The enrichment was purified by picking isolated black colonies from lactate/Te(IV) agar plates, followed by repeated streaking and picking. The isolate, strain MLTeJB, grew in aqueous Te(IV)-medium if provided with a small amount of sterile solid phase material (e.g., agar plug; glass beads). Strain MLTeJB grew at high concentrations of Te(IV) (~8 mM) by oxidizing lactate to acetate plus formate, while reducing Te(IV) to Te(0). Other electron acceptors that were found to sustain growth were tellurate, selenate, selenite, arsenate, nitrate, nitrite, fumarate and oxygen. Notably, growth on arsenate, nitrate, nitrite and fumarate did not result in the accumulation of formate, implying that in these cases lactate was oxidized to acetate plus CO 2 . Strain MLTeJB is a low G + C Gram positive motile rod with pH, sodium, and temperature growth optima at 8.5–9.0, 0.5–1.5 M, and 40°C, respectively. The epithet Bacillus beveridgei strain MLTeJB T is proposed.

California↗

USGS2013

Limited denitrification in glacial deposit aquifers having thick unsaturated zones (Long Island, USA)

The goal of this study was to demonstrate how the extent of denitrification, which is indirectly related to dissolved organ carbon and directly related to oxygen concentrations, can also be linked to unsaturated-zone thickness, a mappable aquifer property. Groundwater from public supply and monitoring wells in Northport on Long Island, New York state (USA), were analyzed for denitrification reaction progress using dissolved N 2 /Ar concentrations by membrane inlet mass spectrometry. This technique allows for discernment of small amounts of excess N 2 , attributable to denitrification. Results show an average 15 % of total nitrogen in the system was denitrified, significantly lower than model predictions of 35 % denitrification. The minimal denitrification is due to low dissolved organic carbon (29.3–41.1 μmol L −1 ) and high dissolved oxygen concentrations (58–100 % oxygen saturation) in glacial sediments with minimal solid-phase electron donors to drive denitrification. A mechanism is proposed that combines two known processes for aquifer re-aeration in unconsolidated sands with thick (>10 m) unsaturated zones. First, advective flux provides 50 % freshening of pore space oxygen in the upper 2 m due to barometric pressure changes. Then, oxygen diffusion across the water-table boundary occurs due to high volumetric air content in the unsaturated-zone catchment area.

Long Island Sound↗

USGS2014

To understand coral disease, look at coral cells

Diseases threaten corals globally, but 40 years on their causes remain mostly unknown. We hypothesize that inconsistent application of a complete diagnostic approach to coral disease has contributed to this slow progress. We quantified methods used to investigate coral disease in 492 papers published between 1965 and 2013. Field surveys were used in 65% of the papers, followed by biodetection (43%), laboratory trials (20%), microscopic pathology (21%), and field trials (9%). Of the microscopic pathology efforts, 57% involved standard histopathology at the light microscopic level (12% of the total investigations), with the remainder dedicated to electron or fluorescence microscopy. Most (74%) biodetection efforts focused on culture or molecular characterization of bacteria or fungi from corals. Molecular and immunological tools have been used to incriminate infectious agents (mainly bacteria) as the cause of coral diseases without relating the agent to specific changes in cell and tissue pathology. Of 19 papers that declared an infectious agent as a cause of disease in corals, only one (5%) used microscopic pathology, and none fulfilled all of the criteria required to satisfy Koch’s postulates as applied to animal diseases currently. Vertebrate diseases of skin and mucosal surfaces present challenges similar to corals when trying to identify a pathogen from a vast array of environmental microbes, and diagnostic approaches regularly used in these cases might provide a model for investigating coral diseases. We hope this review will encourage specialists of disease in domestic animals, wildlife, fish, shellfish, and humans to contribute to the emerging field of coral disease.

EcoHealth↗

USGS2015

Performance of an anaerobic, static bed, fixed film bioreactor for chlorinated solvent treatment

Anaerobic, fixed film, bioreactors bioaugmented with a dechlorinating microbial consortium were evaluated as a potential technology for cost effective, sustainable, and reliable treatment of mixed chlorinated ethanes and ethenes in groundwater from a large groundwater recovery system. Bench- and pilot-scale testing at about 3 and 13,500 L, respectively, demonstrated that total chlorinated solvent removal to less than the permitted discharge limit of 100 μg/L. Various planned and unexpected upsets, interruptions, and changes demonstrated the robustness and reliability of the bioreactor system, which handled the operational variations with no observable change in performance. Key operating parameters included an adequately long hydraulic retention time for the surface area, a constant supply of electron donor, pH control with a buffer to minimize pH variance, an oxidation reduction potential of approximately −200 millivolts or lower, and a well-adapted biomass capable of degrading the full suite of chlorinated solvents in the groundwater. Results indicated that the current discharge criteria can be met using a bioreactor technology that is less complex and has less downtime than the sorption based technology currently being used to treat the groundwater.

Biodegradation↗