Identification of Burrowing Shrimp Food Sources Along an Estuarine Gradient Using Fatty Acid Analysis and Stable Isotope Ratios     

Katelyn M. Bosley  Louise A. Copeman  Brett R. Dumbauld  Keith L. Bosley 《Estuaries and Coasts》2017,40(4):1113-1130

Two species of burrowing shrimp occur in high densities in US West Coast estuaries, the ghost shrimp, Neotrypaea californiensis, and the blue mud shrimp, Upogebia pugettensis. Both species of shrimp are considered ecosystem engineers as they bioturbate and irrigate extensive galleries within the sediment. While their burrows comprise a dominant habitat type in west coast estuaries, little is known about these shrimps’ diet and their role in estuarine food webs. The primary goals of this study were to identify major components of burrowing shrimp diets and detect variation in these diets along an estuarine gradient using combined fatty acid (FA) and stable isotope (SI) analyses. Shrimp and potential food sources including eelgrass blades, epiphytes, Ulva, sedimentary particulate organic matter (SPOM), burrow walls, and particulate organic material (POM) were sampled at different locations within Yaquina Bay, Oregon in August 2012. Both SI and FA analyses indicated differences in food resources assimilated by shrimp along the estuarine gradient. SI values showed that diets for U. pugettensis consisted of carbon sources derived primarily from POM and SPOM, while POM and epiphytes were primary carbon sources for N. californiensis. Shrimp from lower estuarine sites had high levels of 16:1ω7 and 20:5ω3 FAs suggesting their diet is enriched with marine diatoms. Shrimp from upriver showed greater proportion of FA associated with dinoflagellates and terrestrial sources as indicated by a high percentage of C₁₈ polyunsaturated FAs (PUFAs). This is the first study to evaluate diets of these two shrimp species using complimentary FA and SI approaches.  相似文献   

A ∼33,000 year record of environmental change from Arolik Lake, Ahklun Mountains, Alaska, USA     

Darrell S. Kaufman  Feng Sheng Hu  Jason P. Briner  Al Werner  Bruce P. Finney  Irene Gregory-Eaves 《Journal of Paleolimnology》2003,30(4):343-361

A continuous record of lacustrine sedimentation capturing the entire full-glacial period was obtained from Arolik Lake in the Ahklun Mountains, southwestern Alaska. Fluctuations in magnetic susceptibility (MS), grain size, organic-matter (OM) content, C/N ratios, ¹³C, and biogenic silica (BSi) record marked environmental changes within the lake and its watershed during the last 33 cal ka. Age control is provided by 31 ¹⁴C ages on plant macrofossils in four cores between 5.2 and 8.6 m long. Major stratigraphic units are traceable throughout the lake subbottom in acoustical profiles, and provisional ages are derived for six prominent tephra beds, which are correlated among the cores. During the interstadial interval between 33 and 30 cal ka, OM and BSi contents are relatively high with values similar to those of the Pleistocene–Holocene transition, suggesting a similar level of aquatic productivity. During the glacial interval that followed (30–15 cal ka), OM and BSi decrease in parallel with declining summer insolation. OM and BSi values remain relatively uniform compared with the higher variability before and after this interval, and they show no major shifts that might correlate with climate fluctuations evidenced by the local moraine record, nor with other global climate changes. The glacial interval includes a clay-rich unit with a depauperate diatom assemblage that records the meltwater spillover of an ice-dammed lake. The meltwater pulse, and therefore the maximum extent of ice attained by a major outlet glacier of the Ahklun Mountain ice cap, lasted from 24 to 22 cal ka. The Pleistocene–Holocene transition (15–11 cal ka) exhibits the most prominent shifts in OM and BSi, but rapid and dramatic fluctuations in OM and BSi continue throughout the Holocene, indicating pronounced paleoenvrionmental changes.  相似文献   

Comptel Constraints on Unidentified EGRET Sources     

Shu Zhang  Werner Collmar  Volker Schönfelder 《Astrophysics and Space Science》2005,297(1-4):283-290

A major legacy of the EGRET experiment aboard the Compton Gamma-Ray Observatory (CGRO) is the detection of a large number of unidentified Gamma-ray sources. Out of the 271 EGRET sources are 170 not identified yet [Hartman et al. ApJS (123) (1999) 79]. To provide additional information on these unidentified EGRET sources, we derived simultaneous MeV fluxes or flux limits for each source by analyzing the contemporaneous COMPTEL data. Then we compare these MeV fluxes to the extrapolations of the published EGRET spectra. Our results can be grouped into 4 categories [Zhang et al. A&A (421) (2004) 983]: (1) non-constraining upper limits (∼120 sources), (2) hints (> 2 sigma) or detections with consistent MeV fluxes (∼16 sources), (3) enhanced MeV emission (2 sources), and (4) constraining MeV flux limits, requiring a spectral break (∼22 sources). In summary, for about 40 of the unidentified EGRET sources we can provide supplementary spectral information in the neighboring gamma-ray band, which – together with other source parameters – might provide clues to the underlying source nature.  相似文献   

Measurement of Particle-Bound Reactive Oxygen Species in Rubidoux Aerosols   总被引：1，自引：0，他引：1  

Prasanna?Venkatachari  Philip?K.?HopkeEmail author  Brett?D.?Grover  Delbert?J.?Eatough 《Journal of Atmospheric Chemistry》2005,50(1):49-58

The diurnal variations in the concentrations of reactive oxygen species (ROS) in various size fractions were determined for ambient particles in Rubidoux, CA. Sampling of particles was conducted at 3 h intervals using a cascade impactor. The collected particles were reacted with dichlorofluorescin (DCFH), a non-fluorescent probe that fluoresces when oxidized. The factors affecting the diurnal variation in ROS concentration were also investigated with special emphasis on the relation between ROS concentration and the intensity of photochemical reactions where the ozone concentration was taken as an index. The intensity of photochemical reactions was found to be a moderate factor affecting the daytime ROS concentration. The concentration of ROS was found to be higher on the smaller particles of the ambient aerosol. An erratum to this article is available .  相似文献   

Comparative soil CO2 flux measurements and geostatistical estimation methods on Masaya volcano, Nicaragua     

Jennifer L. Lewicki  Deborah Bergfeld  Carlo Cardellini  Giovanni Chiodini  Domenico Granieri  Nick Varley  Cynthia Werner 《Bulletin of Volcanology》2005,68(1):76-90

We present a comparative study of soil CO₂ flux () measured by five groups (Groups 1–5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1–5 measured using the accumulation chamber method at 5-m spacing within a 900 m² grid during a morning (AM) period. These measurements were repeated by Groups 1–3 during an afternoon (PM) period. Measured ranged from 218 to 14,719 g m⁻² day⁻¹. The variability of the five measurements made at each grid point ranged from ±5 to 167%. However, the arithmetic means of fluxes measured over the entire grid and associated total CO₂ emission rate estimates varied between groups by only ±22%. All three groups that made PM measurements reported an 8–19% increase in total emissions over the AM results. Based on a comparison of measurements made during AM and PM times, we argue that this change is due in large part to natural temporal variability of gas flow, rather than to measurement error. In order to estimate the mean and associated CO₂ emission rate of one data set and to map the spatial distribution, we compared six geostatistical methods: arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods. While the total CO₂ emission rates estimated using the different techniques only varied by ±4.4%, the maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of , but a variety of geostatistical methods are appropriate to estimate the total CO₂ emission rate from a study area, which is a primary goal in volcano monitoring research.Editorial responsibility: H Shinohara  相似文献   

Potential predictability of dry and wet periods: Sicily and Elbe-Basin (Germany)   总被引：8，自引：1，他引：7  

I. Bordi  K. Fraedrich  F.-W. Gerstengarbe  P. C. Werner  A. Sutera 《Theoretical and Applied Climatology》2004,77(3-4):125-138

Summary The purpose of this paper is to evaluate a viable tool for the potential predictability of dry and wet spells. We select two regions in Europe that have distinct precipitation regimes: Sicily and Elbe basin (Germany). The analysis of dryness and wetness in these regions from 1951 to 2000 is based on the Standardized Precipitation Index (SPI) computed on a long-time scale (two years) and the evaluation of their time-space variability is carried out using Principal Component Analysis. Results suggest that periodicities ranging from 3.4 to 12 years characterise the SPI signals in both regions and essentially drive the main dry and wet occurrences. In Sicily, at variance with the Elbe basin, superimposed to this variability there is also a clearly detectable linear trend that is perhaps related to long-term periodicity. Moreover, the shift in phase found between the common periods implies that often on the longer time scale if the Elbe region has dry conditions, Sicily is wet and viceversa. The reconstruction of the SPI time series by considering the periodicity that greatly contribute to the total power spectrum variance gives good results and provides good opportunities for predictability.  相似文献   

Arrays: The heart and soul of SIRTF     

Michael W. Werner  Peter R. Eisenhardt 《Experimental Astronomy》1994,3(1-4):109-116

This paper describes the status of NASA's Space Infrared Telescope Facility (SIRTF) program. SIRTF will be a cryogenically cooled observatory for infrared astronomy from space and is planned for launch early in the next decade. It will be the first cryogenic space observatory to make extensive use of the powerful infrared detector array technology discussed at this conference. We summarize a newly developed SIRTF mission concept and show how the availability of detector arrays has shaped the scientific rationale for SIRTF, and how the arrays themselves have become part of the definition of the SIRTF mission.  相似文献   

Eddy Covariance Measurements On Mountain Slopes: The Advantage Of Surface-Normal Sensor Orientation Over A Vertical Set-Up   总被引：1，自引：1，他引：0  

Peter Geissbühler  Rolf Siegwolf  Werner Eugster 《Boundary-Layer Meteorology》2000,96(3):371-392

The measurement of scalar fluxes employing the eddy covariance method is a widely used experimental approach,for which the flow distortion due to obstacles (e.g., sensor mounts and mast)is a well-known but not fully solved problem. In order to reduce flow distortion we installed a sonic anemometer in a surface-normal orientationrelative to the terrain slope, and a second instrument in a verticalposition at a horizontal distance of 1.54 m from the first instrumentWe found a significant reduction in the rotation angle necessary for the coordinaterotation procedure in the x-z plane whencomputing 30-minute flux averages with the surface-normal orientation. In 91% of all cases this rotation angleremained within the angle of incidence of ±10° recommended bythe manufacturer. In contrast, only 24% of the measurements taken with the vertically mounted anemometer were obtained at an angle of incidencewithin ±10°, and 3% were outside the ±30° range specified for an acceptable operation.A data quality test based on the variance of vertical windspeed normalized with friction velocity (_w/u_*) revealed problems for application under stable conditions due to large uncertainties in the determination of the Monin–Obukhov stability parameter z/L. An alternative test using the bulk drag coefficient C_D revealed other problems related to the dependence of C_D on z/z₀, the measuring height normalized by the roughness length, which do not appear to be constantin complex terrain. With both tests, a tendency for a slightly improved dataquality was found for the surface normal set-up, which, however, proved statistically insignificant.It is concluded that the surface-normal set-up of a sonic anemometer significantly reduces flow distortion by thesensor head. Although the surface-normal mounting position therefore appears to be the preferred one, with decreased flow distortion and a slightly improved data quality, no significant differences in turbulent quantities were found between the two set-uppositions. Hence, the consequences for short-term measurements of massand energy fluxes with a surface-normal set-up in complex terrain appearto be relevant only if single flux events are to be inspected, while for long-term measurements of integrated fluxes both the surface-normaland vertical installation of the sonic anemometer are adequate,indicating that eddy covariance measurements in complex terrain are lessdelicate than expected.  相似文献   

Die verteilung der Lichtschwachen Sterne im Offenen Sternhaufen NGC 2477     

Werner Lohmann 《Astrophysics and Space Science》1973,24(2):531-533

The relative frequency of the fainter stars increases from the centre of the cluster to the boundary.  相似文献   

Die masse von M33     

Werner Lohmann 《Astrophysics and Space Science》1974,29(1):61-62

According to the Bottlinger law the mass of M33 is determined with (1.29±0.23)×10¹⁰ M from measurements of the velocities of the neutral hydrogen by Warneret al. (1973).

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Mitteilungen Serie A.  相似文献