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At the University of Vermont, an interdisciplinary faculty team developed an introductory watershed science field course. This course honed field skills and catalyzed communication across water-related disciplines without requiring specific prerequisites. Five faculty (geology, engineering, geography, natural resources) taught the four-credit course, highlighting interactions between the hydrosphere, biosphere, and solid Earth. The course, based in the Winooski River watershed, followed the river from its headwaters downstream to its outlet in Lake Champlain focusing on data collection and analysis methods, while exploring threats to this freshwater ecosystem. This course was offered as a summer field course in 2007. Student learning was assessed using weekly summative assignments and final presentations incorporating field data and acquired knowledge. Attitude and knowledge surveys, administered before and after this first year, documented increased self-assessed learning, affinity for the field learning environment, and that the course provided training relevant to various disciplines. The fiscally unsustainable summer model, and course evaluations guided major revisions to the course. The second offering, in 2009, met weekly during spring term to provide students with context before a two-week field component. This field component was held immediately after classes ended to avoid the need to pay faculty summer salaries.

Microbial metabolism is the engine that drives global biogeochemical cycles, yet many key transformations are carried out by microbial consortia over short spatiotemporal scales that elude detection by traditional analytical approaches. We investigate syntrophic sulfur cycling in the 'pink berry' consortia of the Sippewissett Salt Marsh through an integrative study at the microbial scale. The pink berries are macroscopic, photosynthetic microbial aggregates composed primarily of two closely associated species: sulfide-oxidizing purple sulfur bacteria (PB-PSB1) and sulfate-reducing bacteria (PB-SRB1). Using metagenomic sequencing and (34) S-enriched sulfate stable isotope probing coupled with nanoSIMS, we demonstrate interspecies transfer of reduced sulfur metabolites from PB-SRB1 to PB-PSB1. The pink berries catalyse net sulfide oxidation and maintain internal sulfide concentrations of 0-500 μm. Sulfide within the berries, captured on silver wires and analysed using secondary ion mass spectrometer, increased in abundance towards the berry interior, while δ(34) S-sulfide decreased from 6‰ to -31‰ from the exterior to interior of the berry. These values correspond to sulfate-sulfide isotopic fractionations (15-53‰) consistent with either sulfate reduction or a mixture of reductive and oxidative metabolisms. Together this combined metagenomic and high-resolution isotopic analysis demonstrates active sulfur cycling at the microscale within well-structured macroscopic consortia consisting of sulfide-oxidizing anoxygenic phototrophs and sulfate-reducing bacteria.

Microbial metabolism is the engine that drives global biogeochemical cycles, yet many key transformations are carried out by microbial consortia over short spatiotemporal scales that elude detection by traditional analytical approaches. We investigate syntrophic sulfur cycling in the 'pink berry' consortia of the Sippewissett Salt Marsh through an integrative study at the microbial scale. The pink berries are macroscopic, photosynthetic microbial aggregates composed primarily of two closely associated species: sulfide-oxidizing purple sulfur bacteria (PB-PSB1) and sulfate-reducing bacteria (PB-SRB1). Using metagenomic sequencing and (34) S-enriched sulfate stable isotope probing coupled with nanoSIMS, we demonstrate interspecies transfer of reduced sulfur metabolites from PB-SRB1 to PB-PSB1. The pink berries catalyse net sulfide oxidation and maintain internal sulfide concentrations of 0-500 μm. Sulfide within the berries, captured on silver wires and analysed using secondary ion mass spectrometer, increased in abundance towards the berry interior, while δ(34) S-sulfide decreased from 6‰ to -31‰ from the exterior to interior of the berry. These values correspond to sulfate-sulfide isotopic fractionations (15-53‰) consistent with either sulfate reduction or a mixture of reductive and oxidative metabolisms. Together this combined metagenomic and high-resolution isotopic analysis demonstrates active sulfur cycling at the microscale within well-structured macroscopic consortia consisting of sulfide-oxidizing anoxygenic phototrophs and sulfate-reducing bacteria.

A novel and promising application of a geochemical tool adapted to medical science is the thermodynamic and kinetic modeling of the behavior of minerals in fluids similar to lung fluids (or simulated lung fluids, SLF). Reaction-path modeling for chrysotile, anorthite, K-feldspar, talc, muscovite, kaolinite, albite, and quartz under physiologic conditions in SLF gives dissolution times for these minerals as: chrysotile < anorthite < K-feldspar < talc < muscovite = kaolinite = albite = quartz. For the reaction of these minerals with SLF, hydroxylapatite (a mineral initially supersaturated in SLF) and several other secondary minerals were predicted to form (e.g., mesolite is predicted to precipitate during dissolution reactions of other [Al.sup.3+]-containing minerals). Batch experiments using SLF and a brucite/chrysotile mineral mixture confirm that hydroxylapatite forms during reactions in SLF, potentially a function of having a seed crystal in the brucite, chrysotile, or hydromagnesite (predicted to form from brucite dissolution) present. Moreover, SEM analysis of lung tissue also confirms the formation of calcium phosphates (e.g., hydroxylapatite). Reaction-path modeling of minerals under physiologic conditions provides insight into mineral behavior in the body; predicted mineralization pathways associated with pleural plaques and the predicted formation of [Al.sup.3+]-bearing minerals during reaction-path modeling deserve attention when considering pathologies in the body. Keywords: Medical mineralogy, mineral dissolution, Geochemist workbench, reaction-path modeling, lung mineralogy DOI: 10.2138/am.2010.3434

The Richmond Mine at Iron Mountain, Shasta County, California, USA provides an excellent opportunity to study the chemical and biological controls on acid mine drainage (AMD) generation in situ, and to identify key factors controlling solution chemistry. Here we integrate four years of field-based geochemical data with 16S rRNA gene clone libraries and rRNA probe-based studies of microbial population structure, cultivation-based metabolic experiments, arsenopyrite surface colonization experiments, and results of intermediate sulfur species kinetics experiments to describe the Richmond Mine AMD system. Extremely acidic effluent (pH between 0.5 and 0.9) resulting from oxidation of approximately 1 × 105 to 2 × 105 moles pyrite/day contains up to 24 g/1 Fe, several g/1 Zn and hundreds of mg/l Cu. Geochemical conditions change markedly over time, and are reflected in changes in microbial populations. Molecular analyses of 232 small subunit ribosomal RNA (16S rRNA) gene sequences from six sites during a sampling time when lower temperature (0.8) conditions predominated show the dominance of Fe-oxidizing prokaryotes such as Ferroplasma and Leptospirillum in the primary drainage communities. Leptospirillum group III accounts for the majority of Leptospirillum sequences, which we attribute to anomalous physical and geochemical regimes at that time. A couple of sites peripheral to the main drainage, "Red Pool" and a pyrite "Slump," were even higher in pH (>1) and the community compositions reflected this change in geochemical conditions. Several novel lineages were identified within the archaeal Thermoplasmatales order associated with the pyrite slump, and the Red Pool (pH 1.4) contained the only population of Acidithiobacillus. Relatively small populations of Sulfobacillus spp. and Acidithiobacillus caldus may metabolize elemental sulfur as an intermediate species in the oxidation of pyritic sulfide to sulfate. Experiments show that elemental sulfur which forms on pyrite surfaces is resistant to most oxidants; its solublization by unattached cells may indicate involvement of a microbially derived electron shuttle. The detachment of thiosulfate (S2O32-) as a leaving group in pyrite oxidation should result in the formation and persistence of tetrathionate in low pH ferric iron-rich AMD solutions. However, tetrathionate is not observed. Although a S2O32--like species may form as a surface-bound intermediate, data suggest that Fe3+ oxidizes the majority of sulfur to sulfate on the surface of pyrite. This may explain why microorganisms that can utilize intermediate sulfur species are scarce compared to Fe-oxidizing taxa at the Richmond Mine site.