Utilization of <Emphasis Type="Italic">Spartina</Emphasis>- and <Emphasis Type="Italic">Phragmites</Emphasis>-Derived Dissolved Organic Matter by Bacteria and Ribbed Mussels (<Emphasis Type="Italic">Geukensia demissa</Emphasis>) from Delaware Bay Salt Marshes     

Karen L. Bushaw-Newton  Danielle A. Kreeger  Sarah Doaty  David J. Velinsky 《Estuaries and Coasts》2008,31(4):694-703

Phragmites australis has been invading Spartina-alterniflora-dominated salt marshes throughout the mid-Atlantic. Although, Phragmites has high rates of primary production, it is not known whether this species supports lower trophic levels of a marsh food web in the same manner as Spartina. Using several related photochemical and biological assays, we compared patterns of organic matter flow of plant primary production through a key salt marsh metazoan, the ribbed mussel (Geukensia demissa), using a bacterial intermediate. Dissolved organic matter (DOM) was derived from plants collected from a Delaware Bay salt marsh and grown in the laboratory with ¹⁴C-CO₂. Bacterial utilization of plant-derived DOM measured as carbon mineralization revealed that both species provided bioavailable DOM to native salt marsh bacteria. Total carbon mineralization after 19 days was higher for Spartina treatments (36% ¹⁴CO₂ ± 3 SE) compared with Phragmites treatments (29% ±2 SE; Wilcoxon–Kruskal–Wallis rank sums test, P < 0.01). Pre-exposing DOM to natural sunlight only enhanced or decreased bioavailability of the DOM to the bacterioplankton during initial measurements (e.g., 7 days or less) but these differences were not significant over the course of the incubations. Mixtures of ¹⁴C-labeled bacterioplankton (and possibly organic flocs) from ¹⁴C-DOM treatments were cleared by G. demissa at similar rates between Spartina and Phragmites treatments. Moreover, ¹⁴C assimilation efficiencies for material ingested by mussels were high for both plant sources ranging from 74% to 90% and not significantly different between plant sources. Sunlight exposure did not affect the nutritional value of the bacterioplankton DOM assemblage for mussels. There are many possible trophic and habitat differences between Spartina- and Phragmites-dominated marshes that could affect G. demissa but the fate of vascular plant dissolved organic carbon in the DOM to bacterioplankton to mussel trophic pathway appears comparable between these marsh types.  相似文献   

Concentration of Ciprofloxacin in Brazilian Hospital Effluent and Preliminary Risk Assessment: A Case Study     

Ayrton F. Martins  Tibiriçá G. Vasconcelos  Danielle M. Henriques  Carla da S. Frank  Armin König  Klaus Kümmerer 《洁净——土壤、空气、水》2008,36(3):264-269

This study was carried out to evaluate the occurrence of the fluoroquinolone antimicrobial agent ciprofloxacin (CIP) in the effluent of the Hospital of the Federal University of Santa Maria (HUSM). Measured environmental concentrations (MECs) of CIP in the hospital wastewater, both before (P1) and after (P2) cesspit/filter system treatment (CFTS), were determined by means of solid phase extraction and reversed‐phase liquid chromatography with fluorescence detection (LC‐FLD) and reversed‐phase liquid chromatography with mass spectrometric detection (LC‐MS/MS). The MECs (n = 7 daily composed samples) were 19 to 155 μg L^–1 (average: 54 ± 21 μg L^–1) and 32 to 99 μg L^–1 (average: 65 ± 45 μg L^–1) in P1 and P2, respectively. No relevant removal was observed from P1 to P2. In a worst case scenario, the final effluent was regarded as MECs of surface water. These MECs were generally 5 to 20,000‐fold higher than what was previously known. If the present data is drawn on to form a model of the situation in developing countries, the picture provides a first rough indication that the environmental risk associated with the use and emission of pharmaceuticals into the environment in developing countries might be higher than in developed countries.  相似文献   

Evaluating Copper Behavior in Urban Surface Waters Under Anthropic Influence. A Case Study from the Igua?u River, Brazil     

Fernando F. Sodré  Danielle C. Schnitzler  Elizabeth W. O. Scheffer  Marco T. Grassi 《Aquatic Geochemistry》2012,18(5):389-405

The goal of this work was to investigate the changes in copper behavior in Igua?u River, a body of water strongly affected by urban inputs. This work was carried out in a subtropical Brazilian watershed suffering with high loads of raw sewage discharges from the Metropolitan Region of Curitiba. A comparison between sampling sites located upstream and downstream from the urban region revealed that human inputs are able to modify the water chemistry of the river in a short distance basis, that is, approximately nine miles. Probably, the most important alterations were the creation of an anaerobic environment as well as the enhancement of humic-coated suspended solids. These two aspects were determinant to explain the high concentrations observed for particulate copper (57% of total recoverable copper) and dissolved copper sulfide species (13%) in the water column. Copper in the sediment was also higher in the downstream site, probably due to the sedimentation of the Cu-enriched particles. However, copper sulfides at the bottom sediment may also be a potential source for the metal in the water column due to the creation of anaerobic conditions in both compartments. Labile copper concentration was not affected by the changes in water chemistry. Despite the fact that sewage discharges motivate the enhancement of organic matter, but not the increase in potential complexing agents, additional ligands such as chloride, carbonates, and anthropogenic dissolved organic ligands can be now computed as a part of the labile fraction.  相似文献   

On Deriving Plasma Velocity Information from CDS/NIS Observations: Application to the Dynamics of Blinkers     

David Hamilton Brooks  Danielle Bewsher 《Solar physics》2006,234(2):257-272

Using standard instrument software and two independently developed data reduction and analysis procedures, we re-examine the accuracy of plasma velocity information derived from data obtained by the Solar and Heliospheric Observatory (SOHO)–Coronal Diagnostic Spectrometer (CDS). We discuss only the Ov 629 Å line data obtained by the Normal Incidence Spectrometer (NIS) and analyse a quiet Sun (QS) and active region (AR) dataset. Using the QS data, we demonstrate that the well-known North-South tilt in wavelength along the NIS slit varies significantly with time, which is not accounted for in the standard CDS correction procedures. In addition, when residual N – S trends exist in the data after processing, they may not be detected, nor removed, using the standard analysis software. This underscores the need for careful analysis of velocity results for individual datasets when using standard correction procedures. Furthermore, even when the results obtained by the two independent methods are well correlated (coefficients greater than 0.9), discrepancies in the values of the derived Doppler velocities can remain (95% within ±5 km s^?1). Therefore, we apply the results to examine the velocities obtained for EUV blinkers by previous authors. It is found that a strong correlation exists in the patterns of variation of the blinker velocities (> 0.98), even though there may be differences in their magnitudes. That is, in a clear majority of cases, the methods agree that a blinker is red-shifted or blue-shifted, although the uncertainty in the absolute velocity may be large.  相似文献   

MSFC Stream Model Preliminary Results: Modeling Recent Leonid and Perseid Encounters     

Danielle E. Moser  William J. Cooke 《Earth, Moon, and Planets》2004,95(1-4):141-153

The cometary meteoroid ejection model of Jones and Brown [Physics, Chemistry, and Dynamics of Interplanetary Dust, ASP Conference Series 104 (1996b) 137] was used to simulate ejection from comets 55P/Tempel-Tuttle during the last 12 revolutions, and the last 9 apparitions of 109P/Swift-Tuttle. Using cometary ephemerides generated by the Jet Propulsion Laboratory’s (JPL) HORIZONS Solar System Data and Ephemeris Computation Service, two independent ejection schemes were simulated. In the first case, ejection was simulated in 1 h time steps along the comet’s orbit while it was within 2.5 AU of the Sun. In the second case, ejection was simulated to occur at the hour the comet reached perihelion. A 4th order variable step-size Runge–Kutta integrator was then used to integrate meteoroid position and velocity forward in time, accounting for the effects of radiation pressure, Poynting–Robertson drag, and the gravitational forces of the planets, which were computed using JPL’s DE406 planetary ephemerides. An impact parameter (IP) was computed for each particle approaching the Earth to create a flux profile, and the results compared to observations of the 1998 and 1999 Leonid showers, and the 1993 and 2004 Perseids.  相似文献   

A cyberGIS approach to exploring neighborhood-level social vulnerability for disaster risk management     

Su Yeon Han  Jeon-Young Kang  Fangzheng Lyu  Furqan Baig  Jinwoo Park  Danielle Smilovsky  Shaowen Wang 《Transactions in GIS》2023,27(7):1942-1958

Timely identification of disaster-prone neighborhoods and examination of disparity in disaster exposure are critical for policymakers to plan efficient disaster management strategies. Many studies have investigated racial, ethnic, and geographic disparities and populations most vulnerable to disasters. However, little attention has been paid to the development of easily accessible and reusable tools to enable: (1) the prompt identification of vulnerable neighborhoods; and (2) the examination of social disparity in disaster impact. In this research, we have developed a visual analytics tool that allows users to: (1) delineate neighborhoods based on their selection of variables; and (2) explore which neighborhoods are susceptible to the impacts of disasters based on specific socioeconomic and demographic characteristics. Through an exploration of COVID-19 data in the case study, we revealed that the tool can provide new insights into the identification of vulnerable neighborhoods that need immediate attention for disaster control, management, and relief.  相似文献   

Evidence of biogeomorphic patterning in a low‐relief karst landscape          下载免费PDF全文

Adam C. Watts  Danielle L. Watts  Matthew J. Cohen  James B. Heffernan  Daniel L. McLaughlin  Jonathan B. Martin  David A. Kaplan  Todd Z. Osborne  Leda N. Kobziar 《地球表面变化过程与地形》2014,39(15):2027-2037

Patterned landscapes are often evidence of biotic control on geomorphic processes, emerging in response to coupled ecosystem processes acting at different spatial scales. Self‐reinforcing processes at local scales expand patches, while self‐inhibiting processes, operating at a distance, impose limits to expansion. In Big Cypress National Preserve (BICY) in southwest Florida, isolated forested wetland depressions (cypress domes) appear to be evenly distributed within a mosaic of short‐hydroperiod marshes and pine uplands. To test the hypothesis that the apparent patterning is regular, we characterized frequency distributions and spatial patterns of vegetation communities, surface and bedrock elevation, and soil properties (thickness and phosphorus content). Nearest neighbor distances indicate strongly significant wetland spatial overdispersion, and bedrock elevations exhibited periodic spatial autocorrelation; both observations are consistent with regular patterning. Bedrock elevations and soil P were clearly bimodal, suggesting strong positive feedbacks on wetland patch development. Soil‐surface elevations exhibited weaker bimodality, indicating smoothing of surface morphology by some combination of sediment transport, mineral reprecipitation, and organic matter production. Significant negative autocorrelation of bedrock elevations at scales similar to wetland spacing suggest the presence of distal negative feedbacks on patch expansion. These findings support the inference of regular patterning, and are consistent with the presence of local positive feedbacks among hydroperiod, vegetation productivity and bedrock dissolution. These processes are ultimately constrained by distal negative feedbacks, potentially induced by landscape scale limitations on the water volume required to enable this biogeomorphic mechanism. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Distinct erosional progressions in the Medusae Fossae Formation, Mars, indicate contrasting environmental conditions   总被引：2，自引：0，他引：2  

Kathleen Mandt  Shanaka de Silva  Danielle Wyrick 《Icarus》2009,204(2):471-477

The form of erosional remnants of the Medusae Fossae Formation (MFF) on Mars provide evidence of their development progression and implicate two spatially distinct environments in the equatorial regions of Mars. Ubiquitous yardangs are clearly the product of strong unidirectional winds acting over time on variably indurated deposits. Yardang orientation is used as a proxy to map regional and local wind direction at meso-scale resolution. In other, more limited areas not subjected to strong unidirectional winds, randomly oriented kilometer-scale mesas and buttes are found to be remnants of progressive cliff recession through mass wasting as support is lost from within the MFF lithology at its margins. The differing processes that dominate the formation of the distinctive landforms have implications for meso-scale variations in climate that remain unresolved by current modeling efforts. Additionally, the variability of erosional forms within the deposit emphasizes the overall complexity of this extensive formation.  相似文献   

Two Years of the STEREO Heliospheric Imagers     

Richard A. Harrison  Jackie A. Davies  Alexis P. Rouillard  Christopher J. Davis  Christopher J. Eyles  Danielle Bewsher  Steve R. Crothers  Russell A. Howard  Neil R. Sheeley  Angelos Vourlidas  David F. Webb  Daniel S. Brown  Gareth D. Dorrian 《Solar physics》2009,256(1-2):219-237

Imaging of the heliosphere is a burgeoning area of research. As a result, it is awash with new results, using novel applications, and is demonstrating great potential for future research in a wide range of topical areas. The STEREO (Solar TErrestrial RElations Observatory) Heliospheric Imager (HI) instruments are at the heart of this new development, building on the pioneering observations of the SMEI (Solar Mass Ejection Imager) instrument aboard the Coriolis spacecraft. Other earlier heliospheric imaging systems have included ground-based interplanetary scintillation (IPS) facilities and the photometers on the Helios spacecraft. With the HI instruments, we now have routine wide-angle imaging of the inner heliosphere, from vantage points outside the Sun-Earth line. HI has been used to investigate the development of coronal mass ejections (CMEs) as they pass through the heliosphere to 1 AU and beyond. Synoptic mapping has also allowed us to see graphic illustrations of the nature of mass outflow as a function of distance from the Sun – in particular, stressing the complexity of the near-Sun solar wind. The instruments have also been used to image co-rotating interaction regions (CIRs), to study the interaction of comets with the solar wind and CMEs, and to witness the impact of CMEs and CIRs on planets. The very nature of this area of research – which brings together aspects of solar physics, space-environment physics, and solar-terrestrial physics – means that the research papers are spread among a wide range of journals from different disciplines. Thus, in this special issue, it is timely and appropriate to provide a review of the results of the first two years of the HI investigations.  相似文献   

Effects of three oil spill dispersants on marine bacterial populations: I. Preliminary Study. Quantitative Evolution of Aerobes     

Danielle Marty  Armand Bianchi  Claude Gatellier 《Marine pollution bulletin》1979,10(10):285-287

The effects of three hydrocarbon dispersant agents (Corexit 9527, Hydrogamosol LT and OSR LT 126) on the bacterial flora of the marine environment are analysed in 20-square-metre basins filled with lagoon seawater.Four months after the first treatment, oil slicks were no longer visible, whereas the appearance of the untreated reference slick had hardly changed. The treatment of 10-litre crude-oil slicks causes an appreciable and long lasting increase in the bacterial population.  相似文献