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21.
Daphne Cuvelier Joze Sarrazin Ana Colao Jon Copley Daniel Desbruyres Adrian G. Glover Paul Tyler Ricardo Serro Santos 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2026-2040
Whilst the fauna inhabiting hydrothermal vent structures in the Atlantic Ocean is reasonably well known, less is understood about the spatial distributions of the fauna in relation to abiotic and biotic factors. In this study, a major active hydrothermal edifice (Eiffel Tower, at 1690 m depth) on the Lucky Strike vent field (Mid-Atlantic Ridge (MAR)) was investigated. Video transects were carried out by ROV Victor 6000 and complete image coverage was acquired. Four distinct assemblages, ranging from dense larger-sized Bathymodiolus mussel beds to smaller-sized mussel clumps and alvinocaridid shrimps, and two types of substrata were defined based on high definition photographs and video imagery. To evaluate spatial variation, faunal distribution was mapped in three dimensions. A high degree of patchiness characterizes this 11 m high sulfide structure. The differences observed in assemblage and substratum distribution were related to habitat characteristics (fluid exits, depth and structure orientation). Gradients in community structure were observed, which coincided with an increasing distance from the fluid exits. A biological zonation model for the Eiffel Tower edifice was created in which faunal composition and distribution can be visually explained by the presence/absence of fluid exits. 相似文献
22.
Sean P Healey Jock A Blackard Todd A Morgan Dan Loeffler Greg Jones Jon Songster Jason P Brandt Gretchen G Moisen Larry T DeBlander 《Carbon balance and management》2009,4(1):9
Background
Although significant amounts of carbon may be stored in harvested wood products, the extraction of that carbon from the forest generally entails combustion of fossil fuels. The transport of timber from the forest to primary milling facilities may in particular create emissions that reduce the net sequestration value of product carbon storage. However, attempts to quantify the effects of transport on the net effects of forest management typically use relatively sparse survey data to determine transportation emission factors. We developed an approach for systematically determining transport emissions using: 1) -remotely sensed maps to estimate the spatial distribution of harvests, and 2) - industry data to determine landscape-level harvest volumes as well as the location and processing totals of individual mills. These data support spatial network analysis that can produce estimates of fossil carbon released in timber transport. 相似文献23.
Carolyn Barnes Simon Jennings Jon. T. Barry 《Estuarine, Coastal and Shelf Science》2009,81(3):368-374
Carbon stable isotopes can be used to trace the sources of energy supporting food chains and to estimate the contribution of different sources to a consumer's diet. However, the δ13C signature of a consumer is not sufficient to infer source without an appropriate isotopic baseline, because there is no way to determine if differences in consumer δ13C reflect source changes or baseline variation. Describing isotopic baselines is a considerable challenge when applying stable isotope techniques at large spatial scales and/or to interconnected food chains in open marine environments. One approach is to use filter-feeding consumers to integrate the high frequency and small-scale variation in the isotopic signature of phytoplankton and provide a surrogate baseline, but it can be difficult to sample a single consumer species at large spatial scales owing to rarity and/or discontinuous distribution. Here, we use the isotopic signature of a widely distributed filter-feeder (the queen scallop Aequipecten opercularis) in the north-eastern Atlantic to develop a model linking base δ13C to environmental variables. Remarkably, a single variable model based on bottom temperature has good predictive power and predicts scallop δ13C with mean error of only 0.6‰ (3%). When the model was used to predict an isotopic baseline in parts of the overall study region where scallop were not consistently sampled, the model accounted for 76% and 79% of the large-scale spatial variability (101–104 km) of the δ13C of two fish species (dab Limanda limanda and whiting Merlangus merlangius) and 44% of the δ13C variability in a mixed fish community. The results show that source studies would be significantly biased if a single baseline were applied to food webs at larger scales. Further, when baseline δ13C cannot be directly measured, a calculated baseline value can eliminate a large proportion of the unexplained variation in δ13C at higher trophic levels. 相似文献
24.
Taro Takahashi Stewart C. Sutherland Rik Wanninkhof Colm Sweeney Richard A. Feely David W. Chipman Burke Hales Gernot Friederich Francisco Chavez Christopher Sabine Andrew Watson Dorothee C.E. Bakker Ute Schuster Nicolas Metzl Hisayuki Yoshikawa-Inoue Masao Ishii Takashi Midorikawa Yukihiro Nojiri Arne Krtzinger Tobias Steinhoff Mario Hoppema Jon Olafsson Thorarinn S. Arnarson Bronte Tilbrook Truls Johannessen Are Olsen Richard Bellerby C.S. Wong Bruno Delille N.R. Bates Hein J.W. de Baar 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2075-2076
25.
Jonathan Irwin Suzanne Aigrain Simon Hodgkin Keivan G. Stassun Leslie Hebb Mike Irwin Estelle Moraux Jerome Bouvier Aude Alapini Richard Alexander D. M. Bramich Jon Holtzman Eduardo L. Martín Mark J. McCaughrean Frédéric Pont P. E. Verrier María Rosa Zapatero Osorio 《Monthly notices of the Royal Astronomical Society》2007,380(2):541-550
We present a general recipe for constructing N -body realizations of galaxies comprising near spherical and disc components. First, an exact spherical distribution function for the spheroids (halo and bulge) is determined, such that it is in equilibrium with the gravitational monopole of the disc components. Second, an N -body realization of this model is adapted to the full disc potential by growing the latter adiabatically from its monopole. Finally, the disc is sampled with particles drawn from an appropriate distribution function, avoiding local-Maxwellian approximations. We performed test simulations and find that the halo and bulge radial density profile very closely match their target model, while they become slightly oblate due to the added disc gravity. Our findings suggest that vertical thickening of the initially thin disc is caused predominantly by spiral and bar instabilities, which also result in a radial re-distribution of matter, rather than scattering off interloping massive halo particles. 相似文献
26.
27.
Barriers to adaptation have emerged as key concerns in climate change theory and practice, however there remains little consensus about which barriers are the most significant to different groups and how competing concerns may be addressed. We investigate the significance of different barriers to adaptation for governments, the private sector, and civil society in Australia through a systematic analysis of submissions to the Australian Productivity Commission’s inquiry into barriers to adaptation. Our results show that respondents prioritise barriers differently according to their respective sectors, and that there are competing concerns about which barriers should be addressed first. Nevertheless, some barriers are more persistent in the submissions than others, with governance and policy seen by most groups as being the major impediments to adaptation. We explain the implications of our analysis for adaptation politics and policy. 相似文献
28.
Guangjie Chen Daniel T. Selbie Katherine Griffiths Jon N. Sweetman Morgan Botrel Zofia E. Taranu Sébastien Knops Jennifer Bondy Neal Michelutti John P. Smol Irene Gregory-Eaves 《Journal of Paleolimnology》2014,52(3):185-200
Pronounced climate warming during the past century has been well documented in high-latitude regions. Nonetheless, considerable heterogeneity exists in northern climate trends. We examined the roles of cryospheric landscape and lake depth in modulating the rate and magnitude of local climate responses through a paleolimnological study of lakes from southwest Yukon, Canada. By sampling lakes at varying distances from the Wrangell-St. Elias ice fields, we hypothesized that, for lakes of similar maximum depth, sites closest to the ice fields would be relatively complacent in terms of their chironomid and diatom assemblage changes over the past ~200 years. This hypothesis is based on the moderating effect of the glaciers on local climate, which would be most pronounced in the lakes nearest to the ice fields. However, given the known ecological differences between deep and shallow lakes, we further predicted that, for a given distance from the ice fields, a sediment record from a shallower lake would show the greatest change in stratigraphic subfossil assemblages. Because of the complicated shape of the ice fields, we applied the longitude for each site (which decreases from west to east) to approximate the proximity of our study lakes to the ice fields. Consistent with our predictions, we observed a space-transgressive pattern in the chironomid assemblage turnover that was associated with their proximity to the ice fields (r = ?0.75, P = 0.034, n = 8) across lakes of similar depth (mean maximum depth ± 1, SE = 18.1 ± 2.6 m). Considering a broader network of lakes that represented a greater range in maximum depth (4.9–29 m), we found that differences in subfossil chironomid assemblages between the modern and ca. AD 1800 sediment layers were strongly related to lake depth (r = ?0.77, P < 0.001, n = 15), but failed to detect a significant relationship with latitude or longitude (i.e. our proxy for proximity to the ice fields). Similarly, our comparative high-resolution analyses of two lakes with distinct lake morphometries, but similar proximities to the ice fields, demonstrated the predicted contrasting pattern: we observed pronounced post-1880 changes in the biotic assemblages in the shallow lake and a muted and delayed response (i.e. ~1970s) in the deeper lake. Our findings confirm that cryospheric landscape features can strongly modulate regional climate. Furthermore, our work shows that investigators need to be conscious of how climate change affects the structure and functioning of lakes of different typologies, which influences the way in which paleoclimate signals are recorded and interpreted. 相似文献
29.
Duncan D. Muir Jon D. Blundy Michael C. Hutchinson Alison C. Rust 《Contributions to Mineralogy and Petrology》2014,167(3):1-25
Uturuncu is a dormant volcano in the Altiplano of SW Bolivia. A present day ~70 km diameter interferometric synthetic aperture radar (InSAR) anomaly roughly centred on Uturuncu’s edifice is believed to be a result of magma intrusion into an active crustal pluton. Past activity at the volcano, spanning 0.89 to 0.27 Ma, is exclusively effusive and almost all lavas and domes are dacitic with phenocrysts of plagioclase, orthopyroxene, biotite, ilmenite and Ti-magnetite plus or minus quartz, and microlites of plagioclase and orthopyroxene set in rhyolitic groundmass glass. Plagioclase-hosted melt inclusions (MI) are rhyolitic with major element compositions that are similar to groundmass glasses. H2O concentrations plotted versus incompatible elements for individual samples describe a trend typical of near-isobaric, volatile-saturated crystallisation. At 870 °C, the average magma temperature calculated from Fe–Ti oxides, the average H2O of 3.2 ± 0.7 wt% and CO2 typically <160 ppm equate to MI trapping pressures of 50–120 MPa, approximately 2–4.5 km below surface. Such shallow storage precludes the role of dacite magma emplacement into pre-eruptive storage regions as being the cause of the observed InSAR anomaly. Storage pressures, whole-rock (WR) chemistry and phase assemblage are remarkably consistent across the eruptive history of the volcano, although magmatic temperatures calculated from Fe–Ti oxide geothermometry, zircon saturation thermometry using MI and orthopyroxene-melt thermometry range from 760 to 925 °C at NNO ± 1 log. This large temperature range is similar to that of saturation temperatures of observed phases in experimental data on Uturuncu dacites. The variation in calculated temperatures is attributed to piecemeal construction of the active pluton by successive inputs of new magma into a growing volume of plutonic mush. Fluctuating temperatures within the mush can account for sieve-textured cores and complex zoning in plagioclase phenocrysts, resorption of quartz and biotite phenocrysts and apatite microlites. That Fe–Ti oxide temperatures vary by ~50–100 °C in a single thin section indicates that magmas were not homogenised effectively prior to eruption. Phenocryst contents do not correlate with calculated magmatic temperatures, consistent with crystal entrainment from the mush during magma ascent and eruption. Microlites grew during ascent from the magma storage region. Variability in the proportion of microlites is attributed to differing ascent and effusion rates with faster rates in general for lavas >0.5 Ma compared to those <0.5 Ma. High microlite contents of domes indicate that effusion rates were probably slowest in dome-forming eruptions. Linear trends in WR major and trace element chemistries, highly variable, bimodal mineral compositions, and the presence of mafic enclaves in lavas demonstrate that intrusion of more mafic magmas into the evolving, shallow plutonic mush also occurred further amplifying local temperature fluctuations. Crystallisation and resorption of accessory phases, particularly ilmenite and apatite, can be detected in MI and groundmass glass trace element covariation trends, which are oblique to WRs. Marked variability of Ba, Sr and La in MI can be attributed to temperature-controlled, localised crystallisation of plagioclase, orthopyroxene and biotite within the evolving mush. 相似文献