A Mini-Review of the Contribution of Benthic Microalgae to the Ecology of the Continental Shelf in the South Atlantic Bight     

James L. Pinckney 《Estuaries and Coasts》2018,41(7):2070-2078

Benthic microalgae (BMA) inhabit the upper few centimeters of shelf sediments. This review summarizes the current information on BMA communities in the South Atlantic Bight (SAB) region of the Southeastern US continental shelf to provide insights into the potential role of these communities in the trophodynamics and biogeochemical cycling in shelf waters. Benthic irradiance is generally 2–6% of surface irradiance in the SAB region, providing sufficient light to support BMA primary production over 80–90% of the shelf width. BMA biomass greatly exceeds that of integrated phytoplankton biomass in the overlying water column on an areal basis. The SAB appears to have lower BMA biomass, but higher production than most temperate continental shelves. Annual production estimates average 101 and 89 g C m^?2 year^?1 for 5–20 and >?20 depth intervals, respectively. However, high variation in rates and biomass in time and space make comparisons between studies difficult. Submarine groundwater discharge (SGD) rather than the water column or in situ N regeneration from organic matter maybe the major “new” N source for BMA. The estimated supply of N (1.2 mmol N m^?2 day^?1) by SGD closely approximates the rates needed to support BMA primary production (3.1 to 1.6 mmol N m^?2 day^?1) in the sediments of the SAB. Identifying the source(s) of fixed N supporting the BMA community is essential for understanding the carbon dynamics and net ecosystem metabolism within the large area (76,000 km²) of the continental shelf in the SAB as well other temperate shelves worldwide.  相似文献   

Climate change and energy security: an analysis of policy research     

Marcus DuBois King  Jay Gulledge 《Climatic change》2014,123(1):57-68

The literature on climate change’s impacts on energy security is scattered across disparate fields of research and schools of thought. Much of this literature has been produced outside of the academy by scholars and practitioners working in “think tanks,” government agencies, and international/multilateral institutions. Here we reviewed a selected set of 58 articles and reports primarily from such sources and performed textual analysis of the arguments. Our review of this literature identifies three potential mechanisms for linking climate change and energy security: Climate change may 1) create second-order effects that may exacerbate social instability and disrupt energy systems; 2) directly impact energy supply and/or systems or 3) influence energy security through the effects of climate-related policies. We identify emerging risks to energy security driven by climate mitigation technology choices but find less evidence of climate change’s direct physical impacts. We used both empirical and qualitative selection factors for choosing the grey literature sample. The sources we selected were published in the last 5 years, available through electronic media and were written in language accessible to general policy or academic readers. The organizations that published the literature had performed previous research in the general fields of energy and/or climate change with some analytical content and identified themselves as non-partisan. This literature is particularly valuable to scholars because identifies understudied relationships that can be rigorously assessed through academic tools and methodologies and informs a translational research agenda that will allow scholars to engage with practitioners to address challenges that lie at the nexus of climate change and energy security.  相似文献   

A Framework for Quantitative Assessment of Impacts Related to Energy and Mineral Resource Development     

Seth S. Haines  Jay E. Diffendorfer  Laurie Balistrieri  Byron Berger  Troy Cook  Don DeAngelis  Holly Doremus  Donald L. Gautier  Tanya Gallegos  Margot Gerritsen  Elisabeth Graffy  Sarah Hawkins  Kathleen M. Johnson  Jordan Macknick  Peter McMahon  Tim Modde  Brenda Pierce  John H. Schuenemeyer  Darius Semmens  Benjamin Simon  Jason Taylor  Katie Walton-Day 《Natural Resources Research》2014,23(1):3-17

Natural resource planning at all scales demands methods for assessing the impacts of resource development and use, and in particular it requires standardized methods that yield robust and unbiased results. Building from existing probabilistic methods for assessing the volumes of energy and mineral resources, we provide an algorithm for consistent, reproducible, quantitative assessment of resource development impacts. The approach combines probabilistic input data with Monte Carlo statistical methods to determine probabilistic outputs that convey the uncertainties inherent in the data. For example, one can utilize our algorithm to combine data from a natural gas resource assessment with maps of sage grouse leks and piñon-juniper woodlands in the same area to estimate possible future habitat impacts due to possible future gas development. As another example: one could combine geochemical data and maps of lynx habitat with data from a mineral deposit assessment in the same area to determine possible future mining impacts on water resources and lynx habitat. The approach can be applied to a broad range of positive and negative resource development impacts, such as water quantity or quality, economic benefits, or air quality, limited only by the availability of necessary input data and quantified relationships among geologic resources, development alternatives, and impacts. The framework enables quantitative evaluation of the trade-offs inherent in resource management decision-making, including cumulative impacts, to address societal concerns and policy aspects of resource development.  相似文献   

The trigonometric parallax of the neutron star Geminga     

Jacqueline Faherty  Frederick M. Walter  Jay Anderson 《Astrophysics and Space Science》2007,308(1-4):225-230

We obtained a series of four observations of the isolated neutron star Geminga over an 18 month period using the Advanced Camera for Surveys (ACS) Wide Field Camera (WFC) on the Hubble Space Telescope in order to determine its trigonometric parallax. We find the parallax π=4.0±1.3 mas, corresponding to a distance to Geminga of 250 _?62 ⁺¹²⁰  pc, a result 60% larger than the previously published value. The proper motion is 178.2±1.8 mas/year. In this paper, we describe the analysis techniques in detail since the amplitude of the parallactic shift is smaller than the camera’s pixel size. We fit each star in the images with an appropriate effective PSF and applied a distortion correction to generate stellar positions accurate to 0.01 pixels (～0.5 mas). The 134 stars common to all images serve to establish a reference frame for alignment of the image series. Our observations were made around the times of maximum parallactic shift. We discuss the implications of this new distance measurement for the inferred radius of Geminga, and the neutron star equation of state.  相似文献   

The use of soft X-ray spectromicroscopy to investigate the distribution and composition of organic matter in a diatom frustule and a biomimetic analog     

Lynn Abramson  Sue Wirick  Cindy Lee  Chris Jacobsen  Jay A. Brandes 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1369-1380

Diatoms play a significant role in the global carbon cycle through their role in biogenic silica production and the transport of organic matter to the seafloor. Recent work has shown that silicified diatom frustules contain a significant amount of organic matter, and that the proportion of diatom-bound organic matter increases with depth in the water column and sediments. Here, we investigate the association between organic matter and the mineral phase. We used a combination of scanning transmission X-ray microscopy (STXM) and carbon X-ray absorption near-edge structure (XANES) spectroscopy to characterize the distribution and composition of organic matter in frustules of the diatom Cylindrotheca closterium and a biomimetic silica gel. To our knowledge, this study represents the first successful attempt to simultaneously image and obtain chemical information about the organic matter within a diatom frustule using X-ray spectromicroscopy near the carbon edge. Organic carbon, most likely protein, was distributed throughout the frustules and was not removed by harsh chemical treatment. The physical structure of the frustules appeared to be related to the chemical composition of this organic matter, with aromatic or unsaturated carbon being concentrated in the most intricately patterned regions of the frustule. A similar physical and chemical structure was observed in a biomimetic silica gel precipitated spontaneously with polylysine. These results are consistent with the theory that organic constituents of diatom frustules direct silica precipitation and become incorporated within the silica matrix as it forms. The relationship between organic matter composition and silica morphology, the failure of harsh chemical treatments to remove this organic matter, and the spontaneous nature of the co-precipitation of silica and organic matter indicate some chemical interaction between the siliceous and organic components of diatom frustules. Frustule-bound organic matter should therefore be protected from decomposition in the water column or diagenetic alteration in sediments unless the frustule dissolves.  相似文献   

稠油的成因、预测和深水开采——AAPG和AMGP稠油研讨会的回顾和技术摘要     

Barry Jay Katz  刘春 《海洋地质前沿》2009,25(3):28-31

美国石油地质学家学会（AAPG）联合墨西哥石油地质协会（AMGF）于2006年10月8～10日在Veracruz、Mexica召开了题为“稠油：成因、预测和深水开采”的海德伯研讨会。来自世界各地的90位地质科学家和工程师参加了会议。  相似文献   

Sources and transport of suspended particulates in the Caribbean Sea     

N.Jay Bassin 《Marine Geology》1976,21(4):289-310

Gravimetric and light-scattering studies of total suspended matter reveal that the bulk of this material is introduced into the Caribbean through the passages of the Lesser Antilles, most likely the result of discharge of the Amazon and Orinoco Rivers. A broad suspended-matter high extends northward from the South American coast, apparently related to northward advection at the confluence of the westward-moving Caribbean Current and an easterly coastal countercurrent off Colombia. Particulate matter distribution may be accounted for by transport from the northern and eastern sills, with resuspension in the deep basins playing a minor role. Localized concentrations appear to be entering through the Greater Antillean sills, and then are carried westward by the prevailing currents.  相似文献   

Distribution, condition, and growth of newly settled southern flounder (Paralichthys lethostigma) in the Galveston Bay Estuary, TX     

Lindsay A. Glass  Jay R. Rooker  Richard T. Kraus  G. Joan Holt 《Journal of Sea Research》2008,59(4):259-268

Several flatfish species, including southern flounder (Paralichthys lethostigma) recruit to estuaries during early life. Therefore, evaluation of estuarine sites and habitats that serve as nurseries is critical to conservation and management. The present study used density data in conjunction with biochemical condition and growth measurements to evaluate settlement sites used by southern flounder in the Galveston Bay Estuary (GBE). In 2005, beam-trawl collections were made in three major sections of the GBE (East Bay, Galveston Bay, West Bay). Three sites were sampled in each bay. Within each sampling site, replicate collections were taken from three habitats: 1) marsh edge (< 1 m depth), 2) intermediate zone (10–20 m from marsh interface;  1 m depth), and 3) bay zone (typically > 100 m from marsh interface; depth > 1 m). Average size of southern flounder collected was 12–19 mm standard length, and peak densities occurred in January and February. Catch data indicated that densities of southern flounder were significantly greater in East Bay (2.75 per 100 m²) than in Galveston Bay (0.91 per 100 m²) or in West Bay (0.45 per 100 m²). Densities were statistically similar among habitats. Otolith-based estimates of age indicated that the majority of southern flounder collected were 35–45 days old and derived from early December to early January hatch-dates. Growth rates were similar among bays and among habitats, with the average growth rate being 0.40 mm day^− 1 (range: 0.21–0.76 mm day^− 1). RNA:DNA was above the established baseline value for nutritional stress, indicating that newly settled southern flounder in the GBE were in relatively high condition. Habitat-specific differences in RNA:DNA ratios were not observed; however, ratios were significantly lower in West Bay (average 8.0) than in East Bay (average 9.5) or in Galveston Bay (average 9.8), suggesting the condition of new recruits may vary spatially within the GBE. Findings from the current study suggest density and condition of newly settled southern flounder vary at the bay scale, suggesting that parts of GBE do not function equally as nurseries.  相似文献   

Influence of the Columbia River plume (USA) on the vertical and horizontal distribution of mesozooplankton over the Washington and Oregon shelf     

Peterson  Jay O.; Peterson  William T. 《ICES Journal of Marine Science》2008,65(3):477-483

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Compositional and Isotopic Analytical Methods in Archaeological Micromorphology     

Susan M. Mentzer  Jay Quade 《Geoarchaeology》2013,28(1):87-97

Resin‐impregnated sediment blocks are a by‐product of micromorphological sample processing. These blocks can be further studied using a variety of destructive, nondestructive, and minimally destructive geochemical techniques. X‐ray fluorescence microanalyses conducted on sediment blocks yield semiquantitative major and trace elemental abundances that can be used to generate compositional maps, and to illustrate compositional change within or between archaeological strata and features. Sediment blocks can also be drilled to obtain small sediment samples for stable oxygen and carbon isotopic analyses. Both elemental and isotopic analyses can be conducted in conjunction with micromorphological analyses to yield a holistic picture of archaeological sediment composition, source, and depositional processes. The integration of micromorphological, compositional, and isotopic analyses is used here to aid in the differentiation of calcareous ash and lime plasters from the Neolithic site of Asıklı Höyük, Turkey.  相似文献