Aggregational behavior of the blue mussels Mytilus edulis and Mytilus trossulus: a potential pre‐zygotic reproductive isolation mechanism     

Guangxu Liu  Erin Stapleton  David Innes  Raymond Thompson 《Marine Ecology》2011,32(4):480-487

The blue mussels Mytilus edulis and Mytilus trossulus occur sympatrically and are able to hybridize in populations on the eastern coast of Newfoundland, Canada, presenting an opportunity to study their aggregational behavior. Aggregation behavior may therefore provide insight into post‐settlement interactions and pre‐zygotic reproductive isolation between the species. Three treatments were designed using M. edulis and M. trossulus to investigate their intraspecific and interspecific spatial distribution patterns. With Ripley’s K‐function and Monte Carlo simulation analysis, we found that in the single‐species treatment, M. edulis aggregated significantly but not M. trossulus. Based on results of two‐way ANOVAs, both the number of aggregations and the moving distance were significantly affected by the treatments (single‐species or mixed‐species treatment) and times (24, 48, 72 and 96 h). In further pairwise comparisons using Tukey’s test, M. edulis aggregated differently with or without M. trossulus occupying the same tank, suggesting that the aggregational behavior of M. edulis could be driven by species‐specific chemical cues. The result that M. edulis aggregates intraspecifically may increase the probability of intraspecific fertilization of the spawned gametes and thus function as a pre‐zygotic reproductive isolation mechanism maintaining the blue mussel hybrid zone.  相似文献   

Alternating Gaussian process modulated renewal processes for modeling threshold exceedances and durations     

Erin?M.?SchliepEmail authorView author&#;s OrcID profile  Alan?E.?Gelfand  David?M.?Holland 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(2):401-417

It is often of interest to model the incidence and duration of threshold exceedance events for an environmental variable over a set of monitoring locations. Such data arrive over continuous time and can be considered as observations of a two-state process yielding, sequentially, a length of time in the below threshold state followed by a length of time in the above threshold state, then returning to the below threshold state, etc. We have a two-state continuous time Markov process, often referred to as an alternating renewal process. The process is observed over a truncated time window and, within this window, duration in each state is modeled using a distinct cumulative intensity specification. Initially, we model each intensity over the window using a parametric regression specification. We extend the regression specification adding temporal random effects to enrich the model using a realization of a log Gaussian process over time. With only one type of renewal, this specification is referred to as a Gaussian process modulated renewal process. Here, we introduce Gaussian process modulation to the intensity for each state. Model fitting is done within a Bayesian framework. We clarify that fitting with a customary log Gaussian process specification over a lengthy time window is computationally infeasible. The nearest neighbor Gaussian process, which supplies sparse covariance structure, is adopted to enable tractable computation. We propose methods for both generating data under our models and for conducting model comparison. The model is applied to hourly ozone data for four monitoring sites at different locations across the United States for the ozone season of 2014. For each site, we obtain estimated profiles of up-crossing and down-crossing intensity functions through time. In addition, we obtain inference regarding the number of exceedances, the distribution of the duration of exceedance events, and the proportion of time in the above and below threshold state for any time interval.  相似文献   

Between Environmental Change and Neoliberalism: The Effects of Oil Palm Production on Livelihood Resilience     

Jesse Abrams  Erin C. Pischke  Amarella Eastmond  Chelsea A. Silva  Cassandra Moseley 《社会与自然资源》2019,32(5):548-565

Rural communities worldwide are increasingly confronted with the simultaneous impacts of environmental change dynamics and processes of economic restructuring that diminish traditional sources of state support while shifting investments toward large-scale intensive production models. A key question in this context is how livelihoods are affected by these interacting forces of change and whether new production models can contribute to resilience at the household and community scales. Here we examine the impacts of oil palm production on marginal rural communities in Mexico that have experienced both the economic changes associated with neoliberal policy reforms and the dynamics of environmental change. We find that oil palm production can contribute to livelihood resilience when community members participate in its management and governance and when production is associated with state support, but that the kinds of neoliberal policies promoting oil palm expansion may exacerbate existing community vulnerabilities in the face of environmental change.  相似文献   

The Fate of Haloacetic Acids and Trihalomethanes in an Aquifer Storage and Recovery Program, Las Vegas, Nevada     

James M. Thomas  W. Alan McKay  Erin Cole  James E. Landmeyer  Paul M. Bradley 《Ground water》2000,38(4):605-614

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Mechanisms of ringwoodite formation in shocked meteorites: Evidence from L5 chondrite Dhofar 1970          下载免费PDF全文

Erin L. Walton  Sabrina McCarthy 《Meteoritics & planetary science》2017,52(4):762-776

The formation of the high‐pressure compositional equivalents of olivine and pyroxene has been well‐documented within and surrounding shock‐induced veins in chondritic meteorites, formed by crystallization from a liquid‐ or solid‐state phase transformation. Typically polycrystalline ringwoodite grains have a narrow range of compositions that overlap with those of their olivine precursors, whereas the formation of iron‐enriched ringwoodite has been documented from only a handful of meteorites. Here, we report backscattered electron images, quantitative wavelength‐dispersive spectrometry (WDS) analyses, qualitative WDS elemental X‐ray maps, and micro‐Raman spectra that reveal the presence of Fe‐rich ringwoodite (Fa_44‐63) as fine‐grained (500 nm), polycrystalline rims on olivine (Fa_24‐25) wall rock and as clasts engulfed by shock melt in a previously unstudied L5 chondrite, Dhofar 1970. Crystallization of majorite + magnesiowüstite in the vein interior and metastable mineral assemblages within 35 μm of the vein margin attest to rapid crystallization of a superheated shock melt (>2300 K) from 20─25 GPa to ambient pressure and temperature. The texture and composition of bright polycrystalline ringwoodite rims (Fa_44‐63; MnO 0.01─0.08 wt%) surrounding dark polycrystalline olivine (Fa_8‐14; MnO 0.56─0.65 wt%) implies a solid‐state transformation mechanism in which Fe was preferentially partitioned to ringwoodite. The spatial association between ringwoodite and shock melt suggests that the rapidly fluctuating thermal regimes experienced by chondritic minerals in contact with shock melt are necessary to both drive phase transformation but also to prevent back‐transformation.  相似文献   

The influence of vegetation cover on evapotranspiration atop waste rock piles,Elk Valley,British Columbia     

Erin M. Nicholls  Gordon B. Drewitt  Stephanie Fraser  Sean K. Carey 《水文研究》2019,33(20):2594-2606

Surface mining in the Elk Valley, British Columbia, involves removing vegetation, soil, and rock to access underlying metallurgical coal. Subsequent waste rock is placed into adjacent valleys, frequently burying headwater streams. Due to their coarse texture, waste rock piles increase infiltration and percolation, increasing solute transport and concentration of geochemicals in downstream surface waters. Previous research suggests that weathering solutes are transport limited, and it is hypothesized that revegetation will enhance evapotranspiration (ET) and reduce percolation through the waste rock, potentially reducing loading. This study examined the surface‐atmosphere water and energy exchanges using the eddy covariance technique for three waste rock surfaces with different levels of reclamation: (a) an ~25‐year‐old mixed coniferous forest, (b) a grass site, and (c) bare waste rock. Measurements were taken from May to October in 2013 and 2014. Soil moisture and matric suction were measured to 1‐m depth. Sap flow at the forested site was measured to partition transpiration from total ET. In all years, ET rates were greatest at the forested site, followed by the grass cover and lowest at the bare waste rock site. Growing season ET rates at the forest were 56% higher than grass in 2013 and 35% higher in 2014. At the vegetated sites, climate was the main driver of ET, with high radiation, and warm and dry conditions enhancing fluxes. Maximum ET at these sites corresponded with peak growing season, with vegetation increasing both transpiration and rainfall interception. At the bare rock site, ET was weakly related to atmospheric conditions, and ET rates briefly increased during periods following rainfall when near‐surface soil moisture was enhanced. Transpiration comprised 29% of overall ET at the forest site from late July to early October. Results suggest that vegetation establishment can be incorporated into mine reclamation plans to enhance ET rates and limit percolation, potentially reducing downstream geochemical loads.  相似文献   

A shallow subsurface controlled release facility in Bozeman, Montana, USA, for testing near surface CO2 detection techniques and transport models   总被引：1，自引：0，他引：1  

Lee H. Spangler  Laura M. Dobeck  Kevin S. Repasky  Amin R. Nehrir  Seth D. Humphries  Jamie L. Barr  Charlie J. Keith  Joseph A. Shaw  Joshua H. Rouse  Alfred B. Cunningham  Sally M. Benson  Curtis M. Oldenburg  Jennifer L. Lewicki  Arthur W. Wells  J. Rodney Diehl  Brian R. Strazisar  Julianna E. Fessenden  Thom A. Rahn  James E. Amonette  Jon L. Barr  William L. Pickles  James D. Jacobson  Eli A. Silver  Erin J. Male  Henry W. Rauch  Kadie S. Gullickson  Robert Trautz  Yousif Kharaka  Jens Birkholzer  Lucien Wielopolski 《Environmental Earth Sciences》2010,60(2):227-239

A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO₂ transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO₂ release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO₂ transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO₂ from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO₂ through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented.  相似文献   

Can Water Vapour Raman Lidar Resolve Profiles of Turbulent Variables in the Convective Boundary Layer?     

Volker Wulfmeyer  Sandip Pal  David D. Turner  Erin Wagner 《Boundary-Layer Meteorology》2010,136(2):253-284

High-resolution water vapour measurements made by the Atmospheric Radiation Measurement (ARM) Raman lidar operated at the Southern Great Plains Climate Research Facility site near Lamont, Oklahoma, U.S.A. are presented. Using a 2-h measurement period for the convective boundary layer (CBL) on 13 September 2005, with temporal and spatial resolutions of 10 s and 75 m, respectively, spectral and autocovariance analyses of water vapour mixing ratio time series are performed. It is demonstrated that the major part of the inertial subrange was detected and that the integral scale was significantly larger than the time resolution. Consequently, the major part of the turbulent fluctuations was resolved. Different methods to retrieve noise error profiles yield consistent results and compare well with noise profiles estimated using Poisson statistics of the Raman lidar signals. Integral scale, mixing-ratio variance, skewness, and kurtosis profiles were determined including error bars with respect to statistical and sampling errors. The integral scale ranges between 70 and 130 s at the top of the CBL. Within the CBL, up to the third order, noise errors are significantly smaller than sampling errors and the absolute values of turbulent variables, respectively. The mixing-ratio variance profile rises monotonically from ≈0.07 to ≈3.7 g² kg⁻² in the entrainment zone. The skewness is nearly zero up to 0.6 z/z _i , becomes −1 around 0.7–0.8 z/z _i , crosses zero at about 0.95 z/z _i , and reaches about 1.7 at 1.1 z/z _i (here, z is the height and z _i is the CBL depth). The noise errors are too large to derive fourth-order moments with sufficient accuracy. Consequently, to the best of our knowledge, the ARM Raman lidar is the first water vapour Raman lidar with demonstrated capability to retrieve profiles of turbulent variables up to the third order during daytime throughout the atmospheric CBL.  相似文献   

Investigation of calcareous beach sands in the Akumal and Tulum areas for use in constructed wetlands,Eastern Yucatan Peninsula     

Mark P. S. Krekeler  Erin P. Argyilan  Jill Lepp  Lance E. Kearns 《Environmental Earth Sciences》2009,59(2):411-420

Constructed wetlands can be a low-cost, ecologically based technology to locally treat domestic wastewater prior to discharge. Wetland systems implemented in the resort village of Akumal in the state of Quintana Roo, in the Yucatan Peninsula of Mexico have been considered moderately successful over approximately 10 years of operation. Yet the wide-scale implementation of constructed wetlands has not occurred in the region nor throughout Mexico due largely to the cost of the crushed aggregate used in these systems. Variation in the geotechnical and mineralogical properties of 29 samples of local calcareous beach sands collected from the tourist areas of Akumal and Tulum in the Yucatan, Mexico were analyzed and compared to those of crushed aggregate currently used in constructed wetland systems in Akumal. Powder X-ray diffraction on beach sand samples from Akumal and Tulum indicates that the proportion of aragonite varies from 24 to 84%, calcite varies from 7 to 38% and Mg-calcite varied from 8 to 57% compared to crushed aggregate which consists of 0–25% aragonite and 75–100% calcite. Compared to crushed aggregate beach sands are unimodal and have better uniformity coefficients, making them a better geotechnical choice than crushed sands with respect to these properties. Grain-size of the beach sands is much smaller compared to that of the crushed aggregate currently used in the constructed wetland systems in Akumal which should enhance the efficiency of the filtration of organic matter and bacteria. The average hydraulic conductivity measurements of 0.010 and 0.016 cm/s for beach sands from Akumal and Tulum, respectively are comparable or less than the average of 0.016 cm/s for crushed aggregate currently used in engineered wetland systems. Yet a combination of high bulk porosity, intragranular pores, and the presence of Mg-calcite observed in beach sands may likely result in higher dissolution rates versus the crushed aggregate. Preliminary assessment suggests that the use of local sand may be a technical, economic, and perceptual enhancement to the systems. Still a careful and thorough analysis of the potential environmental and aesthetic impacts of mining beach sands is necessary.  相似文献   

An evaluation of Arctic cloud and radiation processes during the SHEBA year: simulation results from eight Arctic regional climate models   总被引：1，自引：1，他引：0  

K. Wyser  C. G. Jones  P. Du  E. Girard  U. Willén  J. Cassano  J. H. Christensen  J. A. Curry  K. Dethloff  J.-E. Haugen  D. Jacob  M. Køltzow  R. Laprise  A. Lynch  S. Pfeifer  A. Rinke  M. Serreze  M. J. Shaw  M. Tjernström  M. Zagar 《Climate Dynamics》2008,30(2-3):203-223

Eight atmospheric regional climate models (RCMs) were run for the period September 1997 to October 1998 over the western Arctic Ocean. This period was coincident with the observational campaign of the Surface Heat Budget of the Arctic Ocean (SHEBA) project. The RCMs shared common domains, centred on the SHEBA observation camp, along with a common model horizontal resolution, but differed in their vertical structure and physical parameterizations. All RCMs used the same lateral and surface boundary conditions. Surface downwelling solar and terrestrial radiation, surface albedo, vertically integrated water vapour, liquid water path and cloud cover from each model are evaluated against the SHEBA observation data. Downwelling surface radiation, vertically integrated water vapour and liquid water path are reasonably well simulated at monthly and daily timescales in the model ensemble mean, but with considerable differences among individual models. Simulated surface albedos are relatively accurate in the winter season, but become increasingly inaccurate and variable in the melt season, thereby compromising the net surface radiation budget. Simulated cloud cover is more or less uncorrelated with observed values at the daily timescale. Even for monthly averages, many models do not reproduce the annual cycle correctly. The inter-model spread of simulated cloud-cover is very large, with no model appearing systematically superior. Analysis of the co-variability of terms controlling the surface radiation budget reveal some of the key processes requiring improved treatment in Arctic RCMs. Improvements in the parameterization of cloud amounts and surface albedo are most urgently needed to improve the overall performance of RCMs in the Arctic.  相似文献