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New forms of stockholder activism call into question longstanding assumptions underpinning our system of corporate governance. Scholarship has largely failed to explain the basis for these new forms and, in particular, the differences among activists. Activists are not one undifferentiated mass. Both small activist hedge funds and large union-sponsored or -influenced pension funds use governance mechanisms to influence corporate behaviour. Pension funds, however, have a different set of incentives than hedge funds. The beneficiaries of these funds cannot easily switch between consumption and investment by buying or selling their holdings in firms. Thus, instead, institutional investors exercise an embedded ‘governance option’ found within shares of common stock to engage with firms. Organised labour, in particular, now uses its influence in pension funds to motivate progressive change by corporations. This form of activism has the potential to alter the balance of power between workers and capitalists in the era of financial capitalism.

This chapter discusses the differential response of individuals and populations exposed to heavy metals or metalloids and evidence for the evolution of tolerance in exposed populations. It explores the evolution of metal tolerance in aquatic organisms, and discusses approaches used to detect natural selection and the evolution of metal tolerance. Genetic factors can significantly affect the response of individuals or populations exposed to metal pollution. Genetically based tolerance is not lost when individuals are placed into clean environments and is inherited by offspring regardless of whether they are reared in polluted or nonpolluted environments. If tolerance to metal exposure is genetically based, the survivors will constitute a population with an altered genetic composition relative to the preexposure population. Retention of tolerance in animals taken from contaminated sites and maintained in clean conditions is evidence that the tolerance is genetically determined and not acclimation to prevailing conditions.

Insider trading is not widely understood. Insiders of corporations can, in fact, buy and sell shares of those corporations. But, over time, Congress, the courts and the Securities and Exchange Commission (SEC) have imposed significant limits on such trading. The limits are not always clearly marked and the principles underlying them not always consistent. The core principle is that it is illegal to trade if one is in the possession of material, nonpublic information. But the rationality of this principle has been challenged by successive generations of law and economics scholars, most notably Manne, Easterbrook, Epstein, and Bainbridge. Their “economic” analysis of this contested area of the law provides, arguably, at least a more consistent basis upon which to decide when trades by insiders should, in fact, be disallowed. A return to genuine “first principles” generated by the nature of capitalism, however, allows for more powerful insights into the phenomenon and could lead to more effective regulation.

The COVID-19 viral pandemic exposed equity and safety culture gaps in American legal education. Legal education forms part of America’s Critical Infrastructure whose continuity is important to the economy, public safety, democracy, and the national security of the United States. To address the COVID-19 pandemic and prepare for future viral pandemics and safety risks, this article recommends law schools develop a safety culture to foster health, safety, robust educational dialogue, and equity. To guide safety-and-equity-centered decision-making and promote effective legal education during and following the COVID-19 pandemic, this article contends legal education must put health, safety, and equity first. It proposes an ethical framework for legal education that centers diversity and inclusion as the foundation of robust educational dialogue. This article’s interdisciplinary analysis of COVID-19 scientific studies recommends law schools follow the science and exercise extreme caution before convening classes in person or in a hybrid fashion. COVID-19 infection risks serious illness, long-lasting complications, and death. It has preyed on America’s inequities. African-Americans, Native Americans, Latinx Americans, older Americans, and those with certain underlying health conditions including pregnant women face higher levels of hospitalization and death from COVID-19 infection. COVID-19’s inequitable risks may separate those participating in class in person, or online, by race, ethnicity, tribe, age, and health. Law schools must ensure that during the COVID-19 health emergency, hybrid or in-person pedagogical models do not undermine diversity and inclusion that supports educational dialogue and First Amendment values. The COVID-19 pandemic underscores the imperative of putting health, safety, and equity first in legal education.

Corporate law theory finds itself at an impasse, unable to explain or resolve the intense and frequent crises that beset modern capitalism. This impasse is currently expressed in a very public debate about the “purpose” of the corporation. Both sides of this debate – agency theory and stakeholder theory – trace their origins to the deeply problematic ninety-year-old claim of Berle and Means that there is a fundamental separation of ownership from control in the corporation. Both schools maintain that “corporate governance” can solve the problems that beset the modern corporation. Both schools, however, not only failed to anticipate the ongoing corporate crises but have also failed to explain them. They have certainly not managed to prevent them. The re-emerging debate about the purpose of the corporation offers an opportunity to reassess corporate law theory. Applying the insights of the Warwick School on strategic decision-making in firms, I test an alternative approach through a case study of Apple Inc.’s capital structure and dividend policy. I conclude that the corporation is governed by a relatively coherent capitalist class that carries out the dominant economic laws of the capitalist system.

Existential therapy and Jungian analysis share much in common. The early Jung, with his self-professed scientific study and “empirical” description of the human psyche focused strictly on “observed facts,” fancied himself a phenomenologist of sorts, loosely using a philosophical method first described in detail by Edmund Husserl (1859-1938) at the start of the 20th century. In this article, the author, a clinical and forensic psychologist, compares the contemporary practices of existential therapy and Jungian analysis, citing essential similarities and differences, and proposing and describing the complementary synthesis of these two penetrating and potent theoretical orientations in a reimagined form of therapy he calls “existential depth psychology.” He argues here that contemporary existential therapy’s reflexively broad dismissal of depth psychology and its profound clinical wisdom diminishes it immensely. And vice versa. Given the inherent bias against such sagacious, depth-oriented counseling and psychotherapy in today’s increasingly vapid mental health marketplace, Jungian analysis and existential therapy, despite, or really due to, their differences, desperately need each other to become more balanced, whole, efficacious, relevant, and viable humanistic treatment approaches.

Volatile events in the stock market such as the 2010 Flash Crash have sparked concern that financial markets are “rigged” in favor of trading firms that use high frequency trading (“HFT”) systems. We analyze a regulatory change implemented by the SEC in 2007 by examining its effect on a key market metric, the bid-ask spread, an investor cost, and find that the regulatory shift, indeed, disadvantages investors. We link the implementation of this change to a shift in the volume of trades from a low-cost venue to a high-cost venue. We argue that this outcome is predicted by the incentives of the venues, non-profit stock exchanges owned by different types of members. The less-volatile, lower-cost New York Stock Exchange was owned by underwriters and included a specialist system that is less vulnerable to HFT tactics that can disadvantage investors.

The unique behavior of engineered nanomaterials (ENM) in aqueous media and dynamic changes in particle settling, agglomeration and dissolution rates is a challenge to the consistency, reliability and interpretation of standard aquatic hazard bioassay results. While the toxicological endpoints (e.g., survival, growth, reproduction, etc.) in ecotoxicity bioassays are largely applicable to ENMs, the standard methods as written for dissolved substances are confounded by the dynamic settling, agglomeration and dissolution of particulate ENMs during the bioassay. A testing framework was designed to serve as a starting point to identify approaches for the consistent conduct of aquatic hazard tests that account for the behavior of ENMs in test media and suitable data collection to support representative exposure metrology. The framework was demonstrated by conducting three case studies testing ENMs with functionally distinct characteristics and behaviors. Pretests with a temporal sampling of particle concentration, agglomeration and dissolution were conducted on each ENM in test media. Results indicated that a silver nanoparticle (AgNP) powder was not dispersible, a nano-TiO2 powder was dispersible but unstable, and a polyvinylpyrrolidinone-coated AgNP was relatively stable in test media. Based on these functional results, Ceriodaphnia dubia bioassays were conducted to compare different exposure summary methods (nominal, arithmetic average, geometric average, time-weighted average) for calculating and expressing toxicity endpoints. Results indicated that while arithmetic means were effective for expressing the toxicity of more stable materials, time-weighted averaged concentrations were appropriate for the unstable nano-TiO2.

As a semiconductor with wide band gap energy, TiO2 nanoparticles (nano-TiO2) are highly photoactive, and recent efforts have demonstrated phototoxicity of nano-TiO2 to aquatic organisms. However, a dosimetry model for the phototoxicity of nanomaterials that incorporates both direct UV and photo-activated chemical toxicity has not yet been developed. In this study, a set of Hyalella azteca acute toxicity bioassays at multiple light intensities and nano-TiO2 concentrations, and with multiple diel light cycles, was conducted to assess how existing phototoxicity models should be adapted to nano-TiO2. These efforts demonstrated (a) adherence to the Bunsen-Roscoe law for the reciprocity of light intensity and time, (b) no evidence of damage repair during dark periods, (c) a lack of proportionality of effects to environmental nano-TiO2 concentrations, and (d) a need to consider the joint effects of nano-TiO2 phototoxicity and direct UV toxicity.

There is limited information on the chronic effects of nanomaterials to benthic organisms, as well as environmental mitigating factors that might influence this toxicity. The present study aimed to fill these data gaps by examining various growth endpoints (weight gain, instantaneous growth rate, and total protein content) for up to a 21 d sediment exposure of TiO2 nanoparticles (nano-TiO2) to a representative benthic species, Hyalella azteca. An uncoated standard, P25, and an Al(OH)3 coated nano-TiO2 used in commercial products were added to sediment at 20 mg/L or 100 mg/L Under test conditions, UV exposure alone was shown to be a greater cause of toxicity than even these high levels of nano-TiO2 exposure, indicating that different hazards need to be addressed in toxicity testing scenarios. In addition, this study showed the effectiveness of a surface coating on the decreased photoactivity of the material, as the addition of an Al(OH)3 coating showed a dramatic decrease in reactive oxygen species (ROS) production. However, this reduced photoactivity was found to be partially restored when the coating had been degraded, leading to the need for future toxicity tests which examine the implications of weathering events on particle surface coatings.

Toxicityoftitaniumdioxidenanoparticles(nano-TiO2)toaquaticorganismscanbegreatlyincreasedafterexposuretoultraviolet (UV) radiation. This phenomenon has received some attention for water column species; however, investigations of nano-TiO2 phototoxicity for benthic organisms are still limited. In the present study, bioassays of 3 representative benthic organisms (Hyalella azteca, Lumbriculusvariegatus,andChironomusdilutus)wereconductedtoevaluatenano-TiO2phototoxicity.Whenexposedto20mg/Lofnano- TiO2andvariouslightintensities(0-30W/m 2 ),H.aztecawasthemostsensitive,withamedianlethaldoseof40.7(95%confidenceinterval, 36.3-44.7) Wh/m 2 , and hence is a potential model organism in future toxicological guidelines for photoactive nanomaterials to freshwater benthos. Without the presence of nano-TiO2, no mortality was observed in L. variegatus and C. dilutus exposed to UV intensity ranging from 0W/m 2 to 41W/m 2 . However, a sharp drop of H. azteca survival was observed when UV intensity was higher than 9.4W/m 2 , demonstrating the importance of UV-only effects on the ultimate phototoxicity of nanomaterials. Furthermore, both bioavailability and surface attachment of nano-TiO2 onto organisms were affected by the exposure scenario, supported by the exposure scenario-dependent phototoxicity seen in H. azteca and C. dilutus. Overall, the present study demonstrates the importance of species sensitivity and exposure scenarios in future test guidelines of nano-phototoxicity. Environ Toxicol Chem 2014;33:1563-1569. # 2014 SETAC

The dismissal of a senior Facebook employee in connection with the purchase of Facebook shares on a private resale trading platform last year raised new concerns about secondary trading in the securities of private companies and insider trading. This practitioner-oriented essay explores these issues and suggests that startup companies consider adopting a variation on the standard insider trading policy widely adopted by public companies. The discussion is important in light of new attention being paid by regulators to insider trading as well as a debate in Congress about barriers to raising capital for smaller companies. This paper was included as a chapter in Research Handbook on Insider Trading edited by Stephen Bainbridge and published by Elgar.

Zebrafish embryos have been used increasingly to evaluate nanomaterial toxicity. The present study compared phototoxicity of TiO2 nanoparticles with zebrafish at 4 life stages (embryos, yolk-sac larvae, free-swimming larvae, and juvenile) under simulated sunlight using the 96-h standard toxicity assay. Yolk-sac larvae were found to be the most sensitive to TiO2 phototoxicity, suggesting that the widely used zebrafish embryo test may not fully or accurately predict hazard and risk of these nanoparticles to small fish.

This report presents an exhaustive literature review on the toxicity of manufactured ZnO nanoparticles (NPs) to ecological receptors across different taxa: bacteria, algae and plants, aquatic and terrestrial invertebrates and vertebrates. Ecotoxicity studies on ZnO NPs are most abundant in bacteria, and are relatively lacking in other species. These studies suggest relative high acute toxicity of ZnO NPs (in the low mg/l levels) to environmental species, although this toxicity is highly dependent on test species, physico-chemical properties of the material, and test methods. Particle dissolution to ionic zinc and particle-induced generation of reactive oxygen species (ROS) represent the primary modes of action for ZnO NP toxicity across all species tested, and photo-induced toxicity associated with its photocatalytic property may be another important mechanism of toxicity under environmentally relevant UV radiation. Finally, current knowledge gaps within this area are briefly discussed and recommendations for future research are made.

Factor analytic studies suggest that there are six replicable second order cognitive factors. These six factors lend themselves to being interpreted as aspects of Royce's (1964) three "ways of knowing." This view provides a unified explanation of the second and third order factors. We hypothesize that each second order factor represents either the number of cognitive schemata of a particular type that a person possesses or the quality of these schemata, and the types of schemata are linked to "ways of knowing." The division of second order factors into qualitative and quantitative aspects, with the qualitative aspects being more subject to deterioration with age, and the quantitative aspects more trainable and subject to personality influence, provides an avenue for linking cognitive abilities to the other personality traits. The theory also resolves several theoretical problems concerning cognitive abilities, including distinguishing aptitudes from achievements, measuring creativity, and determining the relationship between rote memory and intelligence.

The risks associated with exposure to engineered nanomaterials (ENM) will be determined in part by the processes that control their environmental fate and transformation. These processes act not only on ENM that might be released directly into the environment, but more importantly also on ENM in consumer products and those that have been released from the product. The environmental fate and transformation are likely to differ significantly for each of these cases. The ENM released from actual direct use or from nanomaterial-containing products are much more relevant for ecotoxicological studies and risk assessment than pristine ENM. Released ENM may have a greater or lesser environmental impact than the starting materials, depending on the transformation reactions and the material. Almost nothing is known about the environmental behavior and the effects of released and transformed ENM, although these are the materials that are actually present in the environment. Further research is needed to determine whether the release and transformation processes result in a similar or more diverse set of ENM and ultimately how this affects environmental behavior. This article addresses these questions, using four hypothetical case studies that cover a wide range of ENM, their direct use or product applications, and their likely fate in the environment. Furthermore, a more definitive classification scheme for ENM should be adopted that reflects their surface condition, which is a result of both industrial and environmental processes acting on the ENM. The authors conclude that it is not possible to assess the risks associated with the use of ENM by investigating only the pristine form of the ENM, without considering alterations and transformation processes. Environ. Toxicol. Chem. 2012;31:5059. (C) 2011 SETAC

The collapse of the credit markets over the last year has hit more than just the homebuilding and mortgage sectors of the economy. As interest rates increased, private equity, or "PE," an important new form of financial capital, was also rocked on its heels.

Recent reports concerning the lethal effects of solar ultraviolet-B (UV-B) (290–320 nm) radiation on amphibians suggest that this stressor has the potential to impact some amphibian populations. In this study embryos and larvae of three anuran species, Rana pipiens, Rana clamitans and Rana septentrionalis, were exposed to full-spectrum solar radiation and solar radiation filtered to attenuate UV-B radiation or UV-B and ultraviolet-A (UV-A) (290–380 nm) radiation to determine the effects of each wavelength range on embryo and larval survival. Ambient levels of solar radiation were found to be lethal to all three species under exposure conditions that eliminated shade and refuge. Lethality was ameliorated by filtration of UV-B radiation alone, demonstrating that ambient UV-B radiation is sufficient to cause mortality. Although several studies have qualitatively demonstrated the lethality of UV-B to early life stage amphibians this study demonstrates that the larval life stages of the three species ...

Mass concentration is the standard convention to express exposure in ecotoxicology for dissolved substances. However, nanotoxicology has challenged the suitability of the mass concentration dose metric. Alternative metrics often discussed in the literature include particle number, surface area, and ion release (kinetics, equilibrium). It is unlikely that any single metric is universally applicable to all types of nanoparticles. However, determining the optimal metric for a specific type of nanoparticle requires novel studies to generate supportive data and employ methods to compensate for current analytical capability gaps. This investigation generated acute toxicity data for two standard species (Ceriodaphnia dubia, Pimephales promelas) exposed to five sizes (10, 20, 30, 60, 100 nm) of monodispersed citrate- and polyvinylpyrrolidone-coated silver nanoparticles. Particles were sized by various techniques to populate available models for expressing the particle number, surface area, and dissolved fraction. Results indicate that the acute toxicity of the tested silver nanoparticles is best expressed by ion release, and is relatable to total exposed surface area. Particle number was not relatable to the observed acute silver nanoparticle effects.

Due to their inherent phototoxicity and inevitable environmental release, titanium dioxide nanoparticles (nano-TiO2) are increasingly studied in the field of aquatic toxicology. One of the particular interests is the interactions between nano-TiO2 and natural organic matter (NOM). In this study, a series of experiments was conducted to study the impacts of Suwannee River natural organic matter (SRNOM) on phototoxicity and particle behaviors of nano-TiO2. For Daphnia magna, after the addition of 5mg/L SRNOM, LC50 value decreased significantly from 1.03 (0.89-1.20) mg/L to 0.26 (0.22-0.31) mg/L. For zebrafish larvae, phototoxic LC50 values were 39.9 (95% CI, 25.9-61.2) mg/L and 26.3 (95% CI, 18.3-37.8) mg/L, with or without the presence of 5mg/L SRNOM, respectively. There was no statistically significant change of these LC50 values. The impact of SRNOM on phototoxicity of nano-TiO2 was highly dependent on test species, with D. magna being the more sensitive species. The impact on particle behavior was both qualitatively and quantitatively examined. A global predictive model for particle behavior was developed with a three-way interaction of SRNOM, TiO2 concentration, and time and an additive effect of ionic strength. Based on power analyses, 96-h exposure in bioassays was recommended for nanoparticle-NOM interaction studies. The importance of reactive oxygen species (ROS) quenching of SRNOM was also systematically studied using a novel exposure system that isolates the effects of environmental factors. These experiments were conducted with minimal impacts of other important interaction mechanisms (NOM particle stabilization, NOM UV attenuation, and NOM photosensitization). This study highlighted both the particle stabilization and ROS quenching effects of NOM on nano-TiO2 in an aquatic system. There is an urgent need for representative test materials, together with key environmental factors, for future risk assessment and regulations of nanomaterials.

As a semiconductor with wide band gap energy, TiO2 nanoparticles (nano-TiO2) are highly photoactive, and recent efforts have demonstrated phototoxicity of nano-TiO2 to aquatic organisms. However, a dosimetry model for the phototoxicity of nanomaterials that incorporates both direct UV and photo-activated chemical toxicity has not yet been developed. In this study, a set of Hyalella azteca acute toxicity bioassays at multiple light intensities and nano-TiO2 concentrations, and with multiple diel light cycles, was conducted to assess how existing phototoxicity models should be adapted to nano-TiO2. These efforts demonstrated (a) adherence to the Bunsen-Roscoe law for the reciprocity of light intensity and time, (b) no evidence of damage repair during dark periods, (c) a lack of proportionality of effects to environmental nano-TiO2 concentrations, and (d) a need to consider the joint effects of nano-TiO2 phototoxicity and direct UV toxicity.

The unique or enhanced properties of manufactured nanomaterials (MNs) suggest that their use in nanoenabled products will continue to increase. This will result in increased potential for human and environmental exposure to MNs during manufacturing, use, and disposal of nanoenabled products. Scientifically based risk assessment for MNs necessitates the development of reproducible, standardized hazard testing methods such as those provided by the Organisation of Economic Cooperation and Development (OECD). Currently, there is no comprehensive guidance on how best to address testing issues specific to MN particulate, fibrous, or colloidal properties. This paper summarizes the findings from an expert workshop convened to develop a guidance document that addresses the difficulties encountered when testing MNs using OECD aquatic and sediment test guidelines. Critical components were identified by workshop participants that require specific guidance for MN testing: preparation of dispersions, dose metrics, the importance and challenges associated with maintaining and monitoring exposure levels, and the need for reliable methods to quantify MNs in complex media. To facilitate a scientific advance in the consistency of nanoecotoxicology test results, we identify and discuss critical considerations where expert consensus recommendations were and were not achieved and provide specific research recommendations to resolve issues for which consensus was not reached. This process will enable the development of prescriptive testing guidance for MNs. Critically, we highlight the need to quantify and properly interpret and express exposure during the bioassays used to determine hazard values.

A recent increase in ultraviolet B radiation is one hypothesis advanced to explain suspected or documented declines of the boreal toad (Bufo boreas Baird and Girard, 1852) across much of the western USA, where some experi- ments have shown ambient UV-B can reduce embryo survival. We examined B. boreas occupancy relative to daily UV-B dose at 172 potential breeding sites in Glacier National Park, Montana, to assess whether UV-B limits the distri- bution of toads. Dose estimates were based on ground-level UV-B data and the effects of elevation, local topographic and vegetative features, and attenuation in the water column. We also examined temporal trends in surface UV-B and spring snowpack to determine whether populations are likely to have experienced increased UV-B exposure in recent decades. We found no support for the hypothesis that UV-B limits the distribution of populations in the park, even when we analyzed high-elevation ponds separately. Instead, toads were more likely to breed in water bodies with higher estimated UV-B doses. The lack of a detectable trend in surface UV-B since 1979, combined with earlier snow melt in the region and increasing forest density at high elevations, suggests B. boreas embryos and larvae likely have not experienced increased UV-B. Resume : L'augmentation recente de le rayonnement ultraviolet B est l'une des hypotheses avancees pour expliquer les declins apprehendes ou observes du crapaud de l'ouest (Bufo boreas Baird et Girard, 1852) dans presque tout l'ouest des E.-U.; certaines experiences y ont d'ailleurs demontre que l'UV-B ambiant peut reduire la survie des embryons. Nous avons determine l'occupation du territoire par B. boreas en fonction des doses journalieres d'UV-B a 172 sites potentiels de reproduction dans le parc national Glacier, Montana, afin d'evaluer si l'UV-B limite la repartition des crapauds. Les estimations du dosage ont ete basees sur des mesures d'UV-B au niveau du sol et sur les effets de

The bankruptcy filing in October of last year by the Delphi Corporation, the giant auto-parts supplier spun off by General Motors in a 1999 public offering, sent a shock wave across the American labor movement. The slow grinding down of organized labor, and with it the standard of living of American workers, has been underway for several decades. This attack on the heavily unionized auto sector, however, indicates a new level of aggressiveness by employers. Coming as it did only a few months after the controversial breakaway from the AFL-CIO of several large affiliates to form the new Change to Win Coalition, the Delphi events seemed to confirm the argument by some in the new grouping that organized labor has to look to a new postindustrial economy in order to rebuild. This is no ordinary bankruptcy, however. Rather than pointing to an economy inevitably beyond manufacturing, it represents a strategic innovation intended to exploit the value still extant in our industrial economy. The entire labor movement must confront this important development.

Ultraviolet-B radiation (UV-B, 280–320-nm wavelengths) doses were estimated for 1024 wetlands in six national parks: Acadia (Acadia), Glacier (Glacier), Great Smoky Mountains (Smoky), Olympic (Olympic), Rocky Mountain (Rocky), and Sequoia/ Kings Canyon (Sequoia). Estimates were made using ground-based UV-B data (Brewer spectrophotometers), solar radiation models, GIS tools, field characterization of vegetative features, and quantification of DOC concentration and spectral absorbance. UV-B dose estimates were made for the summer solstice, at a depth of 1 cm in each wetland. The mean dose across all wetlands and parks was 19.3 W-h m )2 (range of 3.4–32.1 W-h m )2 ). The mean dose was lowest in Acadia (13.7 W-h m )2 ) and highest in Rocky (24.4 W-h m )2 ). Doses were significantly different among all parks. These wetland doses correspond to UV-B flux of 125.0 lW cm )2 (range 21.4–194.7 l Wc m )2 ) based on a day length, averaged among all parks, of 15.5 h. Dissolved organic carbon (DOC), a key determinant of water-column UV-B flux, ranged from 0.6 (analytical detection limit) to 36.7 mg C L )1 over all wetlands and parks, and reduced potential maximal UV-B doses at 1-cm depth by 1%–87 %. DOC concentration, as well as its effect on dose, was lowest in Sequoia and highest in Acadia (DOC was equivalent in Acadia, Glacier, and Rocky). Landscape reduction of potential maximal UV-B doses ranged from zero to 77% and was lowest in Sequoia. These regional differences in UV-B wetland dose illustrate the importance of considering all aspects of exposure in evaluating the potential impact of UV-B on aquatic organisms.

The amount, chemical composition, and source of dissolved organic carbon (DOC), together with in situ ultraviolet (UV-B) attenuation, were measured at 1–2 week intervals throughout the summers of 1999, 2000, and 2001 at four sites in Rocky Mountain National Park (Colorado). Eight additional sites, four in Sequoia and Kings Canyon National Park/John Muir Wilderness (California) and four in Glacier National Park (Montana), were sampled during the summer of 2000. Attenuation of UV-B was significantly related to DOC concentrations over the three years in Rocky Mountain (R2 = 0.39, F = 25.71, P < 0.0001) and across all parks in 2000 (R2 = 0.44, F = 38.25, P < 0.0001). The relatively low R2 values, however, reflect significant temporal and spatial variability in the specific attenuation per unit DOC. Fluorescence analysis of the fulvic acid DOC fraction (roughly 600–2,000 Daltons) indicated that the source of DOC significantly affected the attenuation of UV-B. Sites in Sequoia–Kings Canyon were characterized by DOC derived primarily from algal sources and showed much deeper UV-B penetration, whereas sites in Glacier and Rocky Mountain contained a mix of algal and terrestrial DOC-dominated sites, with more terrestrially dominated sites characterized by greater UV-B attenuation per unit DOC. In general, site characteristics that promoted the accumulation of terrestrially derived DOC showed greater attenuation of UV-B per unit DOC; however, catchment vegetation and soil characteristics, precipitation, and local hydrology interacted to make it difficult to predict potential exposure from DOC concentrations.

The recent depletion of stratospheric ozone hasresulted in increased terrestrial ultraviolet-B radi-ation (UV-B, 280–320-nm wavelengths) and isamong the most dramatic examples of humanactivities affecting global ecosystems. Because thenegative effects of UV-B on biological systems arewell-known, increased exposure represents a clearthreat to human health and ecosystems worldwide(Helbling and Zagarese 2003). In 1987, respondingto this threat, representatives from 24 nationssigned the Montreal Protocol, the first in a series oflandmark global agreements designed to preservestratospheric ozone by reducing industrial produc-tion of ozone-depleting compounds (Morrisette1989). These actions have slowed the rate of ozonereduction; however, stratospheric ozone concen-trations are presently at their lowest levels everand, even assuming complete global compliancewith the Montreal Protocol, are not expected toapproach pre-CFC-release levels for 15–45 years(Weatherhead and others 2000).Through the 1970s and 1980s, as UV-B levelsreaching the surface of the earth increased,amphibian species disappeared from many loca-tions worldwide (Middleton and others 2001). Astrong link between amphibian declines and UV-Bhas not yet been demonstrated, but researchershave begun to evaluate patterns of habitat occu-pancy and declines for evidence of UV-Bs influ-ence in nature (Adams and others 2001; Davidsonand others 2001, 2002; Middleton and others 2001)and to assess the risk that UV-B currently poses forwild amphibians (Palen and others 2002). Al-though the causes of specific amphibian declinesand disappearances are usually unclear, a numberof field experiments have shown that UV-B presentin natural sunlight can increase mortality andmalformation rates in embryos of some amphibians(reviewed in Corn 2000; Blaustein and others2003; Licht 2003). In January 1999, biologists fromthe U.S. Environmental Protection Agency (EPA),National Park Service (NPS), U.S. Geological Sur-vey (USGS), and academia convened in Duluth,Minnesota, USA, to discuss how to evaluate therisk that UV-B poses to natural amphibian popu-lations and to design a research project using theParks Research and Intensive Monitoring of Eco-systems Network (PRIMENet).PRIMENet is a joint EPA–NPS program estab-lished to assess the effects of environmentalstressors on ecological systems nationwide (http://www.forestry.umt.edu/research/MFCES/pro-grams/primenet/). PRIMENet encompasses 14national park sites at which UV-B levels aremonitored continuously by Brewer spectropho

An increase in ultraviolet-B (UV-B) radiation has been posited to be a potential factor in the decline of some amphibian population. This hypothesis has received support from laboratory and field experiments showing that current levels of UV-B can cause embryo mortality in some species, but little research has addressed whether UV-B is influencing the distribution of amphibian populations. We compared patterns of amphibian presence to sitespecific estimates of UV-B dose at 683 ponds and lakes in Glacier, Olympic, and Sequoia‐Kings Canyon National Parks. All three parks are located in western North America, a region with a concentration of documented amphibian declines. Sitespecific daily UV-B dose was estimated using modeled and field-collected data to incorporate the effects of elevation, landscape, and water-column dissolved organic carbon. Of the eight species we examined (Ambystoma gracile, Ambystoma macrodactylum, Bufo boreas, Pseudacris regilla, Rana cascadae, Rana leuteiventris, Rana muscosa, Taricha granulosa), two species (T. granulosa and A. macrodactylum) had quadratic relationships with UV-B that could have resulted from negative UV-B effects. Both species were most likely to occur at moderate UV-B levels. Ambystoma macrodactylum showed this pattern only in Glacier National Park. Occurrence of A. macrodactylum increased as UV-B increased in Olympic National Park despite UV-B levels similar to those recorded in Glacier. We also found marginal support for a negative association with UV-B for P. regilla in one of the two parks where it occurred. We did not find evidence of a negative UV-B effect for any other species. Much more work is still needed to determine whether UV-B, either alone or in concert with other factors, is causing widespread population losses in amphibians.