DEVELOPMENT, TESTING, AND APPLICATION OF STRESSOR GRADIENTS IN RURAL, HEADWATER STREAMS IN SOUTHWESTERN ONTARIO

Effective biological monitoring requires a conceptual model of how human activity varies and how this activity affects resident biota. This model can then be used to generate appropriate hypotheses and study designs in response to bioassessment needs. Stressor gradients have the potential to improve this process, but questions about the development and effectiveness of stressor gradients must be addressed before they can be widely applied to biological monitoring. With the aim of developing the most effective and efficient stressor gradient, four gradients were calculated from stressor information differing in level of detail and spatial explicitness for 479 rural, headwater basins. Fine detail gradients also described substantially more variation in the stressor environment than those using coarse detail data. Data that described the location of the stressors within the basin resulted in only minimal improvements to the description of the stressor environment. The responsiveness of aquatic biota to stressor gradients was determined using surveys of aquatic assemblages in 160 small, rural, streams. Canonical correspondence analysis indicated that fish and macroinvertebrates responded to stressor gradients through compositional shifts from intolerant to tolerant taxa as human activity intensified. This response was confounded by a similar compositional shift in response to a gradient of surface geology. Partial Mantel’s tests controlling for the effect of natural gradients indicated that aquatic assemblages are associated to gradients in the human environment. A stressor gradient was applied in the development of an objective method for selecting environmentally stratified, regional reference sites for the purpose of assessing ecological condition in freshwater ecosystems. This method groups potential sites based on their natural environments prior to establishing the degree of human activities occurring at each site within each group. Sites exhibiting the least amount of human activity are then selected to act as reference sites for each group. In addition to having immediate impact on how biological monitoring is conducted in the Southwestern Ontario region, the results of this study can be conceptually applied to bioassessments worldwide. Furthermore, this study can act as the iii foundation for using stressor gradients for the development of predictive models that will aid in planning and management of future activities that may affect aquatic ecosystems

DEVELOPMENT, TESTING, AND APPLICATION OF STRESSOR GRADIENTS IN RURAL, HEADWATER STREAMS IN SOUTHWESTERN ONTARIO

Effective biological monitoring requires a conceptual model of how human activity varies and how this activity affects resident biota. This model can then be used to generate appropriate hypotheses and study designs in response to bioassessment needs. Stressor gradients have the potential to improve this process, but questions about the development and effectiveness of stressor gradients must be addressed before they can be widely applied to biological monitoring. With the aim of developing the most effective and efficient stressor gradient, four gradients were calculated from stressor information differing in level of detail and spatial explicitness for 479 rural, headwater basins. Fine detail gradients also described substantially more variation in the stressor environment than those using coarse detail data. Data that described the location of the stressors within the basin resulted in only minimal improvements to the description of the stressor environment. The responsiveness of aquatic biota to stressor gradients was determined using surveys of aquatic assemblages in 160 small, rural, streams. Canonical correspondence analysis indicated that fish * and macroinvertebrates responded to stressor gradients through compositional shifts from intolerant to tolerant taxa as human activity intensified. This response was confounded by a similar compositional shift in response to a gradient of surface geology. Partial Mantel’s tests controlling for the effect of natural gradients indicated that aquatic assemblages are associated to gradients in the human environment. A stressor gradient was applied in the development of an objective method for selecting environmentally stratified, regional reference sites for the purpose of assessing ecological condition in freshwater ecosystems. This method groups potential sites based on their natural environments prior to establishing the degree of human activities occurring at each site within each group. Sites exhibiting the least amount of human activity are then selected to act as reference sites for each group. In addition to having immediate impact on how biological monitoring is conducted in the Southwestern Ontario region, the results of this study can be conceptually applied to bioassessments worldwide. Furthermore, this study can act as the 111 foundation for using stressor gradients for the development of predictive models that will aid in planning and management of future activities that may affect aquatic ecosystems

New specimens of the basal ornithischian dinosaur Lesothosaurus diagnosticus Galton, 1978 from the Early Jurassic of South Africa

We describe new specimens of the basal ornithischian dinosaur Lesothosaurus diagnosticus Galton, 1978 collected from a bone bed in the Fouriesburg district of the Free State, South Africa. The material was collected from the upper Elliot Formation (Early Jurassic) and represents the remains of at least three different individuals. These individuals are larger in body size than those already known in museum collections and offer additional information on cranial ontogeny in the taxon. Moreover, they are similar in size to the sympatric taxon Stormbergia dangershoeki. The discovery of three individuals at this locality might imply group-living behaviour in this early ornithischian

A Uniform Analysis of the Ly-alpha Forest at z=0 - 5: V. The extragalactic ionizing background at low redshift

In Paper III of our series "A Uniform Analysis of the Ly-alpha forest at z=0 - 5", we presented a set of 270 quasar spectra from the archives of the Faint Object Spectrograph on the Hubble Space Telescope. A total of 151 of these spectra, yielding 906 lines, are suitable for using the proximity effect signature to measure J(\nu_0), the mean intensity of the hydrogen-ionizing background radiation field, at low redshift. Using a maximum likelihood technique and the best estimates possible for each QSO's Lyman limit flux and systemic redshift, we find J(\nu_0)= 7.6^+9.4_-3.0 x 10^-23 ergs s^-1 cm^-2 Hz^-1 sr^-1 at at 0.03 < z < 1.67. This is in good agreement with the mean intensity expected from models of the background which incorporate only the known quasar population. When the sample is divided into two subsamples, consisting of lines with z 1, the values of J(\nu_0) found are 6.5^+38._-1.6 x 10^-23 ergs s^-1 cm^-2 Hz^-1 sr^-1, and 1.0^+3.8_-0.2 x 10^-22 ergs s^-1 cm^-2 Hz^-1 sr^-1, respectively, indicating that the mean intensity of the background is evolving over the redshift range of this data set. Relaxing the assumption that the spectral shapes of the sample spectra and the background are identical, the best fit HI photoionization rates are found to be 6.7 x 10^-13 s^-1 for all redshifts, and 1.9 x 10^-13 s^-1 and 1.3 x 10^-12 s^-1 for z 1, respectively. This work confirms that the evolution of the number density of Ly-alpha lines is driven by a decrease in the ionizing background from z ~ 2 to z ~ 0 as well as by the formation of structure in the intergalactic medium. (Abridged)Comment: 71 LaTeX pages, 20 encapsulated Postscript figures, Accepted for publication in ApJ, Figure 4 available at http://lithops.as.arizona.edu/~jill/QuasarSpectra/ or http://hea-www.harvard.edu/QEDT/QuasarSpectra

Nutrient enrichment effects are conditional on upstream nutrient concentrations: Implications for bioassessment in multi-use catchments.

Human impacts on stream ecosystems are expected to intensify with population growth and climate change. Decisive information on how stream communities respond to cumulative human impacts is therefore integral for protecting streams draining multi-use catchments. To determine cumulative influences of nutrient enrichment and assess more nuanced approaches for the evaluation of human impacts, we present results from one factorial and two gradient assessment designs applied to benthic algae and macroinvertebrate data from 14 mid-order streams in southern Ontario, Canada with pre-existing human impacts (i.e., sewage effluent and agriculture). We found that among stream variability in ecological indicators measured downstream of sewage effluent outfalls confounded our generalized factorial assessment and provided inconclusive information on a known human impact. Despite our gradient assessment also not having strong statistical support, accounting for the extent of nutrient enrichment associated with differences in sewage effluent and agricultural inputs revealed that larger longitudinal changes in stream communities were associated with increased nutrient enrichment. However, re-weighting our nutrient enrichment gradient based on upstream nutrient concentrations to account for nonlinearities in the response of stream communities to nutrient enrichment produced more robust assessment results that were consistent with predicted effects of nutrients on stream ecosystems. Thus, while our factorial assessment suggests that the communities are resistant to nutrients from cumulative human impacts, our targeted gradient assessment demonstrates that the effects of nutrient enrichment are highly conditional on upstream ecosystem conditions. Future assessments may need to go beyond traditional approaches (i.e., impact presence/absence) and more explicitly consider the environmental stressors and their associated complexities related to the impact under investigation

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum