Importance of seep primary production to Lophelia pertusa and associated fauna in the Gulf of Mexico

To investigate the importance of seep primary production to the nutrition of Lophelia pertusa and associated communities and examine local trophic interactions, we analyzed stable carbon, nitrogen, and sulfur compositions in seven quantitative L. pertusa community collections. A significant seep signature was only detected in one of the 35 species tested (Provanna sculpta, a common seep gastropod) despite the presence of seep fauna at the three sample sites. A potential predator of L. pertusa was identified (Coralliophila sp.), and a variety of other trophic interactions among the fauna occupying the coral framework were suggested by the data, including the galatheid crab Munidopsis sp. 2 feeding upon hydroids and the polychaete Eunice sp. feeding upon the sabellid polychaete Euratella sp. Stable carbon abundances were also determined for different sections of L. pertusa skeleton representing different stages in the growth and life of the aggregation. There was no temporal trend detected in the skeleton isotope values, suggesting that L. pertusa settles in these areas only after seepage has largely subsided. Isotope values of individual taxa that were collected from both L. pertusa and vestimentiferan habitats showed decreasing reliance upon seep primary production with average age of the vestimentiferan aggregation, and finally, no seep signature was detected in the coral collections. Together our data suggest that it is the presence of authigenic carbonate substrata, a product of past seep microbial activity, as well as hydrodynamic processes that drive L. pertusa occurrence at seep sites in the Gulf of Mexico, not nutritional dependence upon primary production by seep microbes.     

Volcanism on Io: New insights from global geologic mapping

We produced the first complete, 1:15 M-scale global geologic map of Jupiter’s moon Io, based on a set of monochrome and color Galileo-Voyager image mosaics produced at a spatial resolution of 1 km/pixel. The surface of Io was mapped into 19 units based on albedo, color and surface morphology, and is subdivided as follows: plains (65.8% of surface), lava flow fields (28.5%), mountains (3.2%), and patera floors (2.5%). Diffuse deposits (DD) that mantle the other units cover ∼18% of Io’s surface, and are distributed as follows: red (8.6% of surface), white (6.9%), yellow (2.1%), black (0.6%), and green (∼0.01%). Analyses of the geographical and areal distribution of these units yield a number of results, summarized below. (1) The distribution of plains units of different colors is generally geographically constrained: Red-brown plains occur >±30° latitude, and are thought to result from enhanced alteration of other units induced by radiation coming in from the poles. White plains (possibly dominated by SO₂ + contaminants) occur mostly in the equatorial antijovian region (±30°, 90-230°W), possibly indicative of a regional cold trap. Outliers of white, yellow, and red-brown plains in other regions may result from long-term accumulation of white, yellow, and red diffuse deposits, respectively. (2) Bright (possibly sulfur-rich) flow fields make up 30% more lava flow fields than dark (presumably silicate) flows (56.5% vs. 43.5%), and only 18% of bright flow fields occur within 10 km of dark flow fields. These results suggest that secondary sulfurous volcanism (where a bright-dark association is expected) could be responsible for only a fraction of Io’s recent bright flows, and that primary sulfur-rich effusions could be an important component of Io’s recent volcanism. An unusual concentration of bright flows at ∼45-75°N, ∼60-120°W could be indicative of more extensive primary sulfurous volcanism in the recent past. However, it remains unclear whether most bright flows are bright because they are sulfur flows, or because they are cold silicate flows covered in sulfur-rich particles from plume fallout. (3) We mapped 425 paterae (volcano-tectonic depressions), up from 417 previously identified by Radebaugh et al. (Radebaugh, J., Keszthelyi, L.P., McEwen, A.S., Turtle, E.P., Jaeger, W., Milazzo, M. [2001]. J. Geophys. Res. 106, 33005-33020). Although these features cover only 2.5% of Io’s surface, they correspond to 64% of all detected hot spots; 45% of all hot spots are associated with the freshest dark patera floors, reflecting the importance of active silicate volcanism to Io’s heat flow. (4) Mountains cover only ∼3% of the surface, although the transition from mountains to plains is gradational with the available imagery. 49% of all mountains are lineated and presumably layered, showing evidence of linear structures supportive of a tectonic origin. In contrast, only 6% of visible mountains are mottled (showing hummocks indicative of mass wasting) and 4% are tholi (domes or shields), consistent with a volcanic origin. (5) Initial analyses of the geographic distributions of map units show no significant longitudinal variation in the quantity of Io’s mountains or paterae, in contrast to earlier studies. This is because we use the area of mountain and patera materials as opposed to the number of structures, and our result suggests that the previously proposed anti-correlation of mountains and paterae (Schenk, P., Hargitai, H., Wilson, R., McEwen, A., Thomas, P. [2001]. J. Geophys. Res. 106, 33201-33222; Kirchoff, M.R., McKinnon, W.B., Schenk, P.M. [2011]. Earth Planet. Sci. Lett. 301, 22-30) is more complex than previously thought. There is also a slight decrease in surface area of lava flows toward the poles of Io, perhaps indicative of variations in volcanic activity. (6) The freshest bright and dark flows make up about 29% of all of Io’s flow fields, suggesting active emplacement is occurring in less than a third of Io’s visible lava fields. (7) About 47% of Io’s diffuse deposits (by area) are red, presumably deriving their color from condensed sulfur gas, and ∼38% are white, presumably dominated by condensed SO₂. The much greater areal extent of gas-derived diffuse deposits (red + white, 85%) compared to presumably pyroclast-bearing diffuse deposits (dark (silicate tephra) + yellow (sulfur-rich tephra), 15%) indicates that there is effective separation between the transport of tephra and gas in many Ionian explosive eruptions. Future improvements in the geologic mapping of Io can be obtained via (a) investigating the relationships between different color/material units that are geographically and temporally associated, (b) better analysis of the temporal variations in the map units, and (c) additional high-resolution images (spatial resolutions ∼200 m/pixel or better). These improvements would be greatly facilitated by new data, which could be obtained by future missions.     

Integrating the effects of flood experience on risk perception with responses to changing climate risk

Flood management decision-makers face significant challenges as the climate changes. The perceptions of those affected by floods are critical to the successful implementation of adaptation responses; risk perceptions are affected by how information is communicated and, in turn, perceptions influence expectations on flood risk managers to respond. The links between flood experience, risk perception, and responses by individual households were examined in the Hutt Valley, New Zealand, through a household survey, a workshop and interviews with local government practitioners. Two propositions were tested: (1) that flood experience can influence flood risk perceptions; and (2) that flood experience can stimulate increased risk reduction and adaptation actions where changing climate risk is likely. Perceptions of responsibility for flood management were also examined. The study found that previous flood experience contributes to heightened perception of risk, increased preparedness of households, greater willingness to make household-level changes, greater communication with councils, and more advocacy for spatial planning to complement existing structural protection. Flood-affected households had a stronger preference for central government and communities having flood risk responsibilities, in addition to local government. Those who lacked experience were more likely to be normalised to their prior benign experiences and thus optimistic about flood consequences. These results suggest that harnessing positive aspects of experience and communication of changing risk through engagement strategies could help shift the focus from citizens’ expectation that governments will always provide protection, to a citizen–local government–central government dialogue about the changing character of flood risk and its implications, and build a ‘risk conscious’ society in which ‘sharing and bearing’ is considered desirable.     

Land-use planning for natural hazards in New Zealand: the setting,barriers, ‘burning issues’ and priority actions

Land-use planners have a critical role to play in building vibrant, sustainable and hazard resilient communities in New Zealand. The policy and legal setting for natural hazards planning provides a solid foundation for good practice. But there are many examples of ‘bad practice’ that result in unnecessary risks and, in some cases, exposure to repeat events and potentially devastating impacts. Much, therefore, remains to be done to improve hazards planning policy and practice in New Zealand. This article explores the questions: What role does land-use planning play in managing hazard risks in New Zealand; and what needs to be done to reduce hazard risks and build community resilience? The article starts by describing the milieu within which natural hazards planning takes place. It goes onto outline the stakeholders and institutional and legal setting for natural hazards planning in New Zealand, including barriers to realising the potential of natural hazards planning. This synthesis reveals a number of ‘burning issues’, including the need to: (a) Improve understanding about the nature of hazards; (b) Prioritise risk avoidance (reduction) measures; (c) Provide national guidance for communities exposed to repeat events and address the relocation issue and (d) Mainstream climate change adaptation. Each ‘burning issue’ is discussed, and priority actions are recommended to realise the potential of land-use planning to reduce natural hazard risks and build community resilience in New Zealand. Ultimately, the challenge is to develop a cooperative hazards governance approach that is founded on coordinated policies, laws and institutions, cooperative professional practice and collaborative communities.     

A first principles study of the oxidation energetics and kinetics of realgar

Quantum-mechanical calculations allow resolving and quantifying in detail important aspects of reaction mechanisms such as spin transitions and oxygen dissociation that can be the major rate-limiting steps in redox processes on sulfide and oxide surfaces. In addition, this knowledge can help experimentalists in setting up the framework of rate equations that can be used to describe the kinetics of, e.g., oxidation processes. The unique molecular crystal structure of realgar, As₄S₄ clusters held together by van der Waals bonds, allows for a convenient quantum-mechanical (q.m.) cluster approach to investigate the thermodynamics and kinetic pathways of oxidation. The interaction of As₄S₄ clusters with oxygen and co-adsorbed ions provides a model system for understanding the molecular-scale processes that underpin empirically-derived rate expressions, and provides clues to the oxidation mechanisms of other sulfides and oxides. Two activated processes are shown to dominate the kinetics of oxidation by molecular oxygen: (i) a paramagnetic ³O₂ to diamagnetic ¹O₂ spin transition and (ii) oxygen dissociation on the surface, in that order. The activation energies for the spin transition and O₂ dissociation step were determined to be 1.1 eV (106 kJ/mol) and 0.9 eV (87 kJ/mol), respectively, if molecular oxygen is the only reactant on the surface. In the case of As₄S₄, q.m. calculations reveal that ³O₂ transfers its spin to the cluster and forms a low-spin, peroxo intermediate on the surface before dissociating. The adsorption of a hydroxide ion on the surface proximate to the ³O₂ adsorption site changes the adsorption mechanism by lowering the activation energy barriers for both the spin transition (0.30 eV/29 kJ/mol) and the O₂ dissociation step (0.72 eV/69 kJ/mol). Thus, while spin transition is rate limiting for oxidation with O₂ alone, dissociation becomes the rate-limiting step for oxidation with co-adsorption of OH⁻. First-principles, periodic calculations of the realgar surface show that the energetics and structural changes that accompany oxidation of As₄S₄ clusters on the surface are similar to those involving individual As₄S₄ clusters. Thus, assuming that an As₄S₄ cluster with an adsorbed hydroxyl group is a reasonable approximation of the surface of As₄S₄ at high pH, the theoretically calculated oxidation rate (∼1 × 10⁻¹⁰ mol m⁻² s⁻¹) is of the same order as empirically-derived rates from experiments at T = 298 K, pH = 8, and similar dissolved oxygen concentrations. In addition, the co-adsorption of other anions found in alkaline waters (i.e. carbonate, bicarbonate, sulfate, and sulfite) were shown to energetically promote the oxidation of As₄S₄ (on the order of 5-40 kJ/mol depending on the co-adsorbed anion, OH⁻, , , , or , and accounting for changes in the hydration of products and reactants). The effect of the co-adsorbate on the kinetics and thermodynamics of oxidation is due to each adsorbate modifying the electronic and structural environment of the other adsorption site.Activation-energy barriers due to spin transitions are rarely discussed in the literature as key factors for controlling oxidation rates of mineral surfaces, even though the magnitude of these barriers is enough to alter the kinetics significantly. The attenuation of the activation energy by co-adsorbed anions suggests the possibility of pH− or p(co-adsorbate)-dependent activation energies that can be used to refine oxidation rate laws for sulfide minerals and other, especially semiconducting minerals, such as oxides.     

Reducing long-term remedial costs by transport modeling optimization

The Department of Defense (DoD) Environmental Security Technology Certification Program and the Environmental Protection Agency sponsored a project to evaluate the benefits and utility of contaminant transport simulation-optimization algorithms against traditional (trial and error) modeling approaches. Three pump-and-treat facilities operated by the DoD were selected for inclusion in the project. Three optimization formulations were developed for each facility and solved independently by three modeling teams (two using simulation-optimization algorithms and one applying trial-and-error methods). The results clearly indicate that simulation-optimization methods are able to search a wider range of well locations and flow rates and identify better solutions than current trial-and-error approaches. The solutions found were 5% to 50% better than those obtained using trial-and-error (measured using optimal objective function values), with an average improvement of approximately 20%. This translated into potential savings ranging from 600,000 dollars to 10,000,000 dollars for the three sites. In nearly all cases, the cost savings easily outweighed the costs of the optimization. To reduce computational requirements, in some cases the simulation-optimization groups applied multiple mathematical algorithms, solved a series of modified subproblems, and/or fit "meta-models" such as neural networks or regression models to replace time-consuming simulation models in the optimization algorithm. The optimal solutions did not account for the uncertainties inherent in the modeling process. This project illustrates that transport simulation-optimization techniques are practical for real problems. However, applying the techniques in an efficient manner requires expertise and should involve iterative modification to the formulations based on interim results.     

Potential for satellite remote sensing of ground water

Predicting hydrologic behavior at regional scales requires heterogeneous data that are often prohibitively expensive to acquire on the ground. As a result, satellite-based remote sensing has become a powerful tool for surface hydrology. Subsurface hydrology has yet to realize the benefits of remote sensing, even though surface expressions of ground water can be monitored from space. Remotely sensed indicators of ground water may provide important data where practical alternatives are not available. The potential for remote sensing of ground water is explored here in the context of active and planned satellite-based sensors. Satellite technology is reviewed with respect to its ability to measure ground water potential, storage, and fluxes. It is argued here that satellite data can be used if ancillary analysis is used to infer ground water behavior from surface expressions. Remotely sensed data are most useful where they are combined with numerical modeling, geographic information systems, and ground-based information.     

Global land water storage change from GRACE over 2002–2009; Inference on sea level

Global change in land water storage and its effect on sea level is estimated over a 7-year time span (August 2002 to July 2009) using space gravimetry data from GRACE. The 33 World largest river basins are considered. We focus on the year-to-year variability and construct a total land water storage time series that we further express in equivalent sea level time series. The short-term trend in total water storage adjusted over this 7-year time span is positive and amounts to 80.6 ± 15.7 km³/yr (net water storage excess). Most of the positive contribution arises from the Amazon and Siberian basins (Lena and Yenisei), followed by the Zambezi, Orinoco and Ob basins. The largest negative contributions (water deficit) come from the Mississippi, Ganges, Brahmaputra, Aral, Euphrates, Indus and Parana. Expressed in terms of equivalent sea level, total water volume change over 2002–2009 leads to a small negative contribution to sea level of –0.22 ± 0.05 mm/yr. The time series for each basin clearly show that year-to-year variability dominates so that the value estimated in this study cannot be considered as representative of a long-term trend. We also compare the interannual variability of total land water storage (removing the mean trend over the studied time span) with interannual variability in sea level (corrected for thermal expansion). A correlation of ∼0.6 is found. Phasing, in particular, is correct. Thus, at least part of the interannual variability of the global mean sea level can be attributed to land water storage fluctuations.     

Astronomisches zur Erdgeschichte

Ohne Zusammenfassung