Abiotic hydrogen (H2) sources and sinks near the Mid-Ocean Ridge (MOR) with implications for the subseafloor biosphere.

Free hydrogen (H2) is a basal energy source underlying chemosynthetic activity within igneous ocean crust. In an attempt to systematically account for all H2 within young oceanic lithosphere (<10 Ma) near the Mid-Ocean Ridge (MOR), we construct a box model of this environment. Within this control volume, we assess abiotic H2 sources (∼6 × 1012 mol H2/y) and sinks (∼4 × 1012 mol H2/y) and then attribute the net difference (∼2 × 1012 mol H2/y) to microbial consumption in order to balance the H2 budget. Despite poorly constrained details and large uncertainties, our analytical framework allows us to synthesize a vast body of pertinent but currently disparate information in order to propose an initial global estimate for microbial H2 consumption within young ocean crust that is tractable and can be iteratively improved upon as new data and studies become available. Our preliminary investigation suggests that microbes beneath the MOR may be consuming a sizeable portion (at least ∼30%) of all produced H2, supporting the widely held notion that subseafloor microbes voraciously consume H2 and play a fundamental role in the geochemistry of Earth's ocean-atmosphere system.

Inconsistent correlation of seismic layer 2a and lava layer thickness in oceanic crust.

At mid-ocean ridges with fast to intermediate spreading rates, the upper section of oceanic crust is composed of lavas overlying a sheeted dyke complex. These units are formed by dykes intruding into rocks overlying a magma chamber, with lavas erupting at the ocean floor. Seismic reflection data acquired over young oceanic crust commonly image a reflector known as 'layer 2A', which is typically interpreted as defining the geologic boundary between lavas and dykes. An alternative hypothesis is that the reflector is associated with an alteration boundary within the lava unit. Many studies have used mapped variability in layer 2A thickness to make inferences regarding the geology of the oceanic crust, including volcanic construction, dyke intrusion and faulting. However, there has been no link between the geologic and seismological structure of oceanic crust except at a few deep drill holes. Here we show that, although the layer 2A reflector is imaged near the top of the sheeted dyke complex at fast-spreading crust located adjacent to the Hess Deep rift, it is imaged significantly above the sheeted dykes section at intermediate-spreading crust located near the Blanco transform fault. Although the lavas and underlying transition zone thicknesses differ by about a factor of two, the shallow seismic structure is remarkably similar at the two locations. This implies that seismic layer 2A cannot be used reliably to map the boundary between lavas and dykes in young oceanic crust. Instead we argue that the seismic layer 2A reflector corresponds to an alteration boundary that can be located either within the lava section or near the top of the sheeted dyke complex of oceanic crust.

Survey of Emergency Department Chemical Hazard Preparedness in Michigan, USA: A Seven Year Comparison.

OBJECTIVE: To compare the state of chemical hazard preparedness in emergency departments (EDs) in Michigan, USA between 2005 and 2012. METHODS: This was a longitudinal study involving a 30 question survey sent to ED directors at each hospital listed in the Michigan College of Emergency Physician (MCEP) Directory in 2005 and in 2012. The surveys contained questions relating to chemical, biological, radiological, nuclear, and explosive events with a focus on hazardous material capabilities. RESULTS: One hundred twelve of 139 EDs responded to the 2005 survey compared to 99/136 in 2012. Ten of 27 responses were statistically significant, all favoring an enhancement in disaster preparedness in 2012 when compared to 2005. Questions with improvement included: EDs with employees participating in the Michigan voluntary registry; EDs with decontamination rooms; MARK 1 and cyanide kits available; those planning to use dry decontamination, powered air purifiers, surgical masks, chemical gloves, and surgical gowns; and those wishing for better coordination with local and regional resources. Forty-two percent of EDs in 2012 had greater than one-half of their staff trained in decontamination and 81% of respondents wished for more training opportunities in disaster preparedness. Eighty-four percent of respondents believed that they were more prepared in disaster preparedness in 2012 versus seven years prior. CONCLUSIONS: Emergency departments in Michigan have made significant advances in chemical hazard preparedness between 2005 and 2012 based on survey responses. Despite these improvements, staff training in decontamination and hazardous material events remains a weakness among EDs in the state of Michigan.

A serpentinite-hosted ecosystem: the Lost City hydrothermal field.

The serpentinite-hosted Lost City hydrothermal field is a remarkable submarine ecosystem in which geological, chemical, and biological processes are intimately interlinked. Reactions between seawater and upper mantle peridotite produce methane- and hydrogen-rich fluids, with temperatures ranging from <40 degrees to 90 degrees C at pH 9 to 11, and carbonate chimneys 30 to 60 meters tall. A low diversity of microorganisms related to methane-cycling Archaea thrive in the warm porous interiors of the edifices. Macrofaunal communities show a degree of species diversity at least as high as that of black smoker vent sites along the Mid-Atlantic Ridge, but they lack the high biomasses of chemosynthetic organisms that are typical of volcanically driven systems.

30,000 years of hydrothermal activity at the lost city vent field.

Strontium, carbon, and oxygen isotope data and radiocarbon ages document at least 30,000 years of hydrothermal activity driven by serpentinization reactions at Lost City. Serpentinization beneath this off-axis field is estimated to occur at a minimum rate of 1.2 x 10(-4) cubic kilometers per year. The access of seawater to relatively cool, fresh peridotite, coupled with faulting, volumetric expansion, and mass wasting processes, are crucial to sustain such systems. The amount of heat produced by serpentinization of peridotite massifs, typical of slow and ultraslow spreading environments, has the potential to drive Lost City-type systems for hundreds of thousands, possibly millions, of years.