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111.
Active mud volcanoes on the upper slope of the western Nile deep-sea fan—first results from the P362/2 cruise of R/V Poseidon 总被引:1,自引:0,他引:1
Tomas Feseker Kevin R. Brown Cecile Blanchet Florian Scholz Marianne Nuzzo Anja Reitz Mark Schmidt Christian Hensen 《Geo-Marine Letters》2010,30(3-4):169-186
In February 2008, cruise P362/2 was undertaken aboard R/V Poseidon to the Giza and North Alex mud volcanoes (MVs) on the upper slope of the western Nile deep-sea fan. Emitted fluids were strongly depleted in chloride and rich in hydrocarbons, predominantly of thermogenic origin. In-situ sediment temperature measurements indicate extremely high and moderate levels of activity for the North Alex MV and Giza MV, respectively, and suggest rapid changes from dormant to active stages. Both the physical properties of core sediments (e.g., color and magnetic susceptibility), and their assemblages of micro- and nannofossils point to different sources for the two mud volcanoes. Biostratigraphic dating suggests source depths of 2,100–2,450 mbsf for the Giza MV and 1,150–1,550 mbsf for the North Alex MV. Very high temperatures of up to 70°C in shallow sediments at the North Alex MV can be explained only if the fluid source were warmer and deeper than the sediment source. 相似文献
112.
Melissa M. Foley Benjamin S. Halpern Fiorenza Micheli Matthew H. Armsby Margaret R. Caldwell Caitlin M. Crain Erin Prahler Nicole Rohr Deborah Sivas Michael W. Beck Mark H. Carr Larry B. Crowder J. Emmett Duffy Sally D. Hacker Karen L. McLeod Stephen R. Palumbi Charles H. Peterson Helen M. Regan Mary H. Ruckelshaus Paul A. Sandifer Robert S. Steneck 《Marine Policy》2010
The declining health of marine ecosystems around the world is evidence that current piecemeal governance is inadequate to successfully support healthy coastal and ocean ecosystems and sustain human uses of the ocean. One proposed solution to this problem is ecosystem-based marine spatial planning (MSP), which is a process that informs the spatial distribution of activities in the ocean so that existing and emerging uses can be maintained, use conflicts reduced, and ecosystem health and services protected and sustained for future generations. Because a key goal of ecosystem-based MSP is to maintain the delivery of ecosystem services that humans want and need, it must be based on ecological principles that articulate the scientifically recognized attributes of healthy, functioning ecosystems. These principles should be incorporated into a decision-making framework with clearly defined targets for these ecological attributes. This paper identifies ecological principles for MSP based on a synthesis of previously suggested and/or operationalized principles, along with recommendations generated by a group of twenty ecologists and marine scientists with diverse backgrounds and perspectives on MSP. The proposed four main ecological principles to guide MSP—maintaining or restoring: native species diversity, habitat diversity and heterogeneity, key species, and connectivity—and two additional guidelines, the need to account for context and uncertainty, must be explicitly taken into account in the planning process. When applied in concert with social, economic, and governance principles, these ecological principles can inform the designation and siting of ocean uses and the management of activities in the ocean to maintain or restore healthy ecosystems, allow delivery of marine ecosystem services, and ensure sustainable economic and social benefits. 相似文献
113.
Keun-Hyung Choi Sung-Mi Lee Sang-Min Lim Mark Walton Gyung-Soo Park 《Journal of Oceanography》2010,66(3):307-317
Yellow Sea tidal flats are internationally recognised for their contribution to biological diversity and yet are under enormous
pressure from reclamation, pollution and overexploitation. The benthic macroinfauna community is the dominant community on
these tidal flats and a reliable indicator of benthic environmental changes. We surveyed the current benthic macroinfauna
community of the Ganghwa Southern Tidal Flat, the largest remaining Korean mud flat in the Yellow Sea, in order to examine
changes in the environmental situation of this benthic ecosystem. The results show a significant decline in species diversity
from the last survey made in 2003, and a shift in species composition with appearances of polychaetes indicative of pollution
and physical disturbances and other opportunistic species becoming dominant in both density and biomass. The benthic community
shift observed during the two study periods may be associated with increased nutrient pollution as well as increased physical
disturbances in this area. However, we recognise the limitations of the data both in frequency and scope but believe the significant
changes to the composition of the benthic fauna are sufficient to warrant concern. Observations are required to examine the
extent to which these human activities induce benthic community shift in this tidal flat. 相似文献
114.
115.
We aim to show how some of the important interdisciplinary fixes or solutions to diverse problems observed in fisheries can complement each other. This can be achieved through methodical allocation of the rights pertaining to fisheries and simultaneous implementation of policy instruments to correct for market failures and equity concerns. We emphasize via a roadmap that there are some general principles that should be invoked when choosing between alternative structures of rights. Our examples from Sweden provide evidence of the flexibility of fishing rights and how they can be adapted to integrate fixes from different disciplines into practical fisheries management. 相似文献
116.
Mark A. Shields Monika Kedra 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2057-2064
In late 1980s, a dense network of deep capillary burrows was reported on the Vøring Plateau, Nordic Seas, and associated with a sipunculan belonging to the genus Nephasoma. This sipunculan was responsible for rapid transport of organic matter from the sediment surface down a deep burrow network. Over 460 specimens belonging to the genus Nephasoma were collected from the deep Nordic Seas during four cruises from 2000–2005 and four species identified: Nephasoma abyssorum abyssorum, N. diaphanes diaphanes, N. diaphanes corrugatum and N. lilljeborgi. The species responsible for the deep burrows and rapid subduction of organic matter can now be confirmed as Nephasoma lilljeborgi. Deep burrows associated with N. lilljeborgi were observed on the Vøring Plateau, Bear Island Fan, Svalbard Margin and Yermak Plateau and may be a seabed feature endemic to the Nordic Seas region. N. lilljeborgi could have a significant role in influencing the ecology and geochemistry of the Nordic Seas region. It is recommended that future benthic community studies in the Nordic Seas region confirm the species identity of sipunculan specimens in order to determine the ecological and geochemical importance of the specimens. 相似文献
117.
Mitigation of lunar dust adhesion by surface modification 总被引:2,自引:0,他引:2
Adrienne Dove Genevieve Devaud Xu Wang Mark Crowder Anna Lawitzke Christina Haley 《Planetary and Space Science》2011,59(14):1784-1790
Dust has been recognized as one of the greatest hazards in continued lunar exploration due to its tenacious adhesion to everything with which it comes into contact. Unfortunately, there is little known about the mechanisms of adhesion on widely varying surface types: van der Waals and electrostatic forces are the dominant forces under consideration here. Surface energy, roughness, mechanical properties and electronic properties are all known to contribute to the adhesion characteristics. An optimal solution to mitigate dust adhesion would be to identify the dominant components of the adhesive force and to reduce that force by surface modification. In this study, an ion beam process was used to modify (treat) the surfaces of three dramatically different materials spanning the range of conductor (black Kapton), semiconductor (silicon), and insulator (quartz). Adhesive forces between less than JSC-1 lunar simulants and these virgin/treated surfaces were measured in vacuum using a centrifugal force detachment method. We found that JSC-1 particles adhered less to treated silicon and quartz surfaces, correlated with a reduction in van der Waals force due to a reduced surface energy. The large reduction in adhesion for treated black Kapton is mainly due to the large decrease in the electrostatic (image) force that results from reduced contact charging. Materials in space and on the lunar surface will be directly exposed to high-energy ultraviolet radiation prior to being covered by dust, so the UV irradiation effects on surface adhesion were also examined. Both virgin and treated quartz surfaces are most affected by the UV-irradiation, showing dramatically increased adhesion. 相似文献
118.
Fe and O isotope composition of meteorite fusion crusts: Possible natural analogues to chondrule formation?
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Dominik C. Hezel Graeme M. Poole Jack Hoyes Barry J. Coles Catherine Unsworth Nina Albrecht Caroline Smith Mark Rehkämper Andreas Pack Matthew Genge Sara S. Russell 《Meteoritics & planetary science》2015,50(2):229-242
Meteorite fusion crust formation is a brief event in a high‐temperature (2000–12,000 K) and high‐pressure (2–5 MPa) regime. We studied fusion crusts and bulk samples of 10 ordinary chondrite falls and 10 ordinary chondrite finds. The fusion crusts show a typical layering and most contain vesicles. All fusion crusts are enriched in heavy Fe isotopes, with δ56Fe values up to +0.35‰ relative to the solar system mean. On average, the δ56Fe of fusion crusts from finds is +0.23‰, which is 0.08‰ higher than the average from falls (+0.15‰). Higher δ56Fe in fusion crusts of finds correlate with bulk chondrite enrichments in mobile elements such as Ba and Sr. The δ56Fe signature of meteorite fusion crusts was produced by two processes (1) evaporation during atmospheric entry and (2) terrestrial weathering. Fusion crusts have either the same or higher δ18O (0.9–1.5‰) than their host chondrites, and the same is true for Δ17O. The differences in bulk chondrite and fusion crust oxygen isotope composition are explained by exchange of oxygen between the molten surface of the meteorites with the atmosphere and weathering. Meteorite fusion crust formation is qualitatively similar to conditions of chondrule formation. Therefore, fusion crusts may, at least to some extent, serve as a natural analogue to chondrule formation processes. Meteorite fusion crust and chondrules exhibit a similar extent of Fe isotope fractionation, supporting the idea that the Fe isotope signature of chondrules was established in a high‐pressure environment that prevented large isotope fractionations. The exchange of O between a chondrule melt and an 16O‐poor nebula as the cause for the observed nonmass dependent O isotope compositions in chondrules is supported by the same process, although to a much lower extent, in meteorite fusion crusts. 相似文献
119.
Wangcheng Zhang Dong Wang Mark F. Randolph Alexander M. Puzrin 《国际地质力学数值与分析法杂志》2016,40(17):2312-2338
Quantitative assessment of the risk of submarine landslides is an essential part of the design process for offshore oil and gas developments in deep water, beyond the continental shelf. Landslides may be triggered by a reduction in shear strength of subsea sediments over a given zone, caused for example by seismic activity. Simple criteria are then needed to identify critical conditions whereby the zone of weakness could grow catastrophically to cause a landslide. A number of such criteria have been developed over the last decade, based either on ideas drawn from fracture mechanics, or considering the equilibrium of the initial weakened zone and adjacent process zones of gradually softening material. Accounting for the history of the weak zone initiation is critical for derivation of reliable propagation criteria, in particular considering dynamic effects arising from accumulating kinetic energy of the failing material, which will allow the failure to propagate from a smaller initial zone of weakened sediments. Criteria are developed here for planar conditions, taking full account of such dynamic effects, which are shown to be capable of reducing the critical length of the softened zone by 20% or more compared with criteria based on static conditions. A numerical approach is used to solve the governing dynamic equations for the sliding material, the results from which justify assumptions that allow analytical criteria to be developed for the case where the initial softening occurs instantaneously. The effect of more gradual softening is also explored. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
120.
Richard A. Staff Takeshi Nakagawa Gordon Schlolaut Michael H. Marshall Achim Brauer Henry F. Lamb Christopher Bronk Ramsey Charlotte L. Bryant Fiona Brock Hiroyuki Kitagawa Johannes van der Plicht Rebecca L. Payne Victoria C. Smith Darren F. Mark Alison Macleod Simon P. E. Blockley Jean‐Luc Schwenninger Pavel E. Tarasov Tsuyoshi Haraguchi Katsuya Gotanda Hitoshi Yonenobu Yusuke Yokoyama Suigetsu Project Members 《Boreas: An International Journal of Quaternary Research》2013,42(2):259-266
The varved sediment of Lake Suigetsu (central Japan) provides a valuable opportunity to obtain high‐resolution, multi‐proxy palaeoenvironmental data across the last glacial/interglacial cycle. In order to maximize the potential of this archive, a well‐constrained chronology is required. This paper outlines the multiple geochronological techniques being applied – namely varve counting, radiocarbon dating, tephrochronology (including argon–argon dating) and optically stimulated luminescence (OSL) – and the approaches by which these techniques are being integrated to form a single, coherent, robust chronology. Importantly, we also describe here the linkage of the floating Lake Suigetsu (SG06) varve chronology and the absolute (IntCal09 tree‐ring) time scale, as derived using radiocarbon data from the uppermost (non‐varved) portion of the core. This tie‐point, defined as a distinct (flood) marker horizon in SG06 (event layer B‐07–08 at 1397.4 cm composite depth), is thus derived to be 11 255 to 11 222 IntCal09 cal. years BP (68.2% probability range). 相似文献