Rodent sperm analysis in field-based ecological risk assessment: pilot study at Ravenna army ammunition plant,Ravenna, Ohio

Ecological risk assessment (ERA) guidance recommends that field-truthing efforts proceed when modeled hazard quotients (HQs) suggest that toxicological effects are occurring to site receptors. To date, no field methods have been proposed by the regulatory community that can lead to definitive determinations of acceptable or unacceptable risk for birds and mammals, the two terrestrial classes of receptors that are commonly assessed using the HQ method. This paper describes rodent sperm analysis (RSA) as a viable method to be applied in the field at sites with historical contamination. RSA is capable of detecting biological differences that bear on reproduction, a highly regarded toxicological endpoint of concern in USEPA Superfund-type ERAs. The results of RSA's first application at a study site are reported and discussed. The paper also provides the rationale for RSA's efficacy in the context of Superfund and other environmental cleanup programs, where limited time and money are available to determine and evaluate the field condition.     

A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters

The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO₂) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO₂ production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO₂ production by mineralization as well as CO₂ loss by emission, primary production, and carbonate precipitation in lakes, we estimated that the global lateral DIC export can lie within the range of \( {0.70}_{-0.31}^{+0.27} \) to \( {1.52}_{-0.90}^{+1.09} \) Pg C yr^?1 depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO₂ sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO₂ sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.     

Development of a new scale to measure subjective career success: A mixed‐methods study

Career success is a main focus of career scholars as well as organizational stakeholders. Historically, career success has been conceptualized and measured in an objective manner, mainly as salary, rank, or number of promotions. However, the changing nature of work has also necessitated a change in the way many employees view success, adding a more subjective component. Although there has been theoretical discussion and calls to develop a comprehensive measure of subjective career success, no contemporary comprehensive quantitative measure exists. The goal of this study was to create and validate a measure of subjective career success, titled the Subjective Career Success Inventory (SCSI). The SCSI includes 24 items that address subjective career success via eight dimensions. The scale was developed and validated through four phases of data collection, beginning with interviews and focus groups, followed by item sorting tasks, then item refinement through confirmatory factor analysis, and finally convergent and discriminant validity quantitative analysis. Theoretical and practical implications are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Nexus between polymer support and metal oxide nanoparticles in hybrid nanosorbent materials (HNMs) for sorption/desorption of target ligands

Metal oxide nanoparticles like hydrated ferric oxide (HFO) or hydrated zirconium oxide (HZrO) are excellent sorbents for environmentally significant ligands like phosphate, arsenic, or fluoride, present at trace concentrations. Since the sorption capacity is surface dependent for HFO and HZrO, nanoscale sizes offer significant enhancement in performance. However, due to their miniscule sizes, low attrition resistance, and poor durability they are unable to be used in typical plug-flow column setups. Meanwhile ion exchange resins, which have no specific affinity toward anionic ligands, are durable and chemically stable. By impregnating metal oxide nanoparticles inside a polymer support, with or without functional groups, a hybrid nanosorbent material (HNM) can be prepared. A HNM is durable, mechanically strong, and chemically stable. The functional groups of the polymeric support will affect the overall removal efficiency of the ligands exerted by the Donnan Membrane Effect. For example, the removal of arsenic by HFO or the removal of fluoride by HZrO is enhanced by using anion exchange resins. The HNM can be precisely tuned to remove one type of contaminant over another type. Also, the physical morphology of the support material, spherical bead versus ion exchange fiber, has a significant effect on kinetics of sorption and desorption. HNMs also possess dual sorption sites and are capable of removing multiple contaminants, namely, arsenate and perchlorate, concurrently.     

Population and leaf-level variation of iridoid glycosides in the invasive weed Verbascum thapsus L. (common mullein): implications for herbivory by generalist insects

Plant–insect interactions, which are strongly mediated by chemical defenses, have the potential to shape invasion dynamics. Despite this, few studies have quantified natural variation in key defensive compounds of invasive plant populations, or how those defenses relate to levels of herbivory. Here, we evaluated variation in the iridoid glycosides aucubin and catalpol in rosette plants of naturally occurring, introduced populations of the North American invader, Verbascum thapsus L. (common mullein; Scrophulariaceae). We examined two scales that are likely to structure interactions with insect herbivores—among populations and within plant tissues (i.e., between young and old leaves). We additionally estimated the severity of damage incurred at these scales due to insect chewing herbivores (predominantly grasshoppers and caterpillars), and evaluated the relationship between iridoid glycoside content and leaf damage. We found significant variation in iridoid glycoside concentrations among populations and between young and old leaves, with levels of herbivory strongly tracking leaf-level investment in defense. Specifically, across populations, young leaves were highly defended by iridoids (averaging 6.5× the concentration present in old leaves, and containing higher proportions of the potentially more toxic iridoid, catalpol) and suffered only minimal damage from generalist herbivores. In contrast, old leaves were significantly less defended and accordingly more substantially utilized. These findings reveal that quantitative variation in iridoid glycosides is a key feature explaining patterns of herbivory in an introduced plant. In particular, these data support the hypothesis that defenses limit the ability of generalists to feed on mullein’s well-defended young leaves, resulting in minimal losses of high-quality tissue, and increasing performance of this introduced species.     

Experimental tree removal in tallgrass prairie: variable responses of flora and fauna along a woody cover gradient

Woody plant encroachment is a worldwide phenomenon in grassland and savanna systems whose consequence is often the development of an alternate woodland state. Theoretically, an alternate state may be associated with changes in system state variables (e.g., species composition) or abiotic parameter shifts (e.g., nutrient availability). When state-variable changes are cumulative, such as in woody plant encroachment, the probability of parameter shifts increases as system feedbacks intensify over time. Using a Before-After Control-Impact (BACI) design, we studied eight pairs of grassland sites undergoing various levels of eastern redcedar (Juniperus virginiana) encroachment to determine whether responses of flora and fauna to experimental redcedar removal differed according to the level of pretreatment redcedar cover. In the first year after removal, herbaceous plant species diversity and evenness, woody plant evenness, and invertebrate family richness increased linearly with pretreatment redcedar cover, whereas increases in small-mammal diversity and evenness were described by logarithmic trends. In contrast, increases in woody plant diversity and total biomass of terrestrial invertebrates were accentuated at levels of higher pretreatment cover. Tree removal also shifted small-mammal species composition toward a more grassland-associated assemblage. During the second year postremoval, increases in herbaceous plant diversity followed a polynomial trend, but increases in most other metrics did not vary along the pretreatment cover gradient. These changes were accompanied by extremely high growing-season precipitation, which may have homogenized floral and faunal responses to removal. Our results demonstrate that tree removal increases important community metrics among grassland flora and fauna within two years, with some responses to removal being strongly influenced by the stage of initial encroachment and modulated by climatic variability. Our results underscore the importance of decisive management for reversing the effects of woody plant encroachment in imperiled grassland ecosystems.     

Telomere dynamics in the Sydney rock oyster (<Emphasis Type="Italic">Saccostrea glomerata</Emphasis>): an investigation into the effects of age,tissue type,location and time of sampling

Telomere length has been purported as a biomarker for age and could offer a non-lethal method for determining the age of wild-caught individuals. Molluscs, including oysters and abalone, are the basis of important fisheries globally and have been problematic to accurately age. To determine whether telomere length could provide an alternative means of ageing molluscs, we evaluated the relationship between telomere length and age using the commercially important Sydney rock oyster (Saccostrea glomerata). Telomere lengths were estimated from tissues of known age individuals from different age classes, locations and at different sampling times. Telomere length tended to decrease with age only in young oysters less than 18 months old, but no decrease was observed in older oysters aged 2–4 years. Regional and temporal differences in telomere attrition rates were also observed. The relationship between telomere length and age was weak, however, with individuals of identical age varying significantly in their telomere length making it an imprecise age biomarker in oysters.     

Behavioural inertia places a top marine predator at risk from environmental change in the Benguela upwelling system

In variable environments, organisms are bound to track environmental changes if they are to survive. Most marine mammals and seabirds are colonial, central-place foragers with long-term breeding-site fidelity. When confronted with environmental change, such species are potentially constrained in their ability to respond to these changes. For example, if environmental conditions deteriorate within their limited foraging range, long-lived species favour adult survival and abandon their current breeding effort, which ultimately influences population dynamics. Should poor conditions persist over several seasons, breeding-site fidelity may force animals to continue breeding in low-quality habitats instead of emigrating towards more profitable grounds. We assessed the behavioural response of a site-faithful central-place forager, the Cape gannet Morus capensis, endemic to the Benguela upwelling system, to a rapid shift in the distribution and abundance of its preferred prey, small pelagic shoaling fish. We studied the distribution and the abundance of prey species, and the diet, foraging distribution, foraging effort, energy requirements, and breeding success of gannets at Malgas Island (South Africa) over four consecutive breeding seasons. Facing a rapid depletion of preferred food within their foraging range, Cape gannets initially increased their foraging effort in search of their natural prey. However, as pelagic fish became progressively scarcer, breeding birds resorted to scavenging readily available discards from a nearby demersal fishery. Their chicks cannot survive on such a diet, and during our 4-year study, numbers of breeding birds at the colony decreased by 40% and breeding success of the remaining birds was very low. Such behavioural inflexibility caused numbers of Cape gannets breeding in Namibia to crash by 95% following over-fishing of pelagic fish in the 1970s. In the context of rapid environmental changes, breeding-site fidelity of long-lived species may increase the risk of local or even global extinction, rendering these species particularly vulnerable to global change.     

Allometric scaling predicts preferences for burned patches in a guild of East African grazers

The high herbivore diversity in savanna systems has been attributed to the inherent spatial and temporal heterogeneity related to the quantity and quality of food resources. Allometric scaling predicts that smaller-bodied grazers rely on higher quality forage than larger-bodied grazers. We replicated burns at varying scales in an East African savanna and measured visitation by an entire guild of larger grazers ranging in size from hare to elephant. We found a strong negative relationship between burn preference and body mass with foregut fermenters preferring burns to a greater degree than hindgut fermenters. Burns with higher quality forage were preferred more than burns with lower quality forage by small-bodied grazers, while the opposite was true for large-bodied grazers. Our results represent some of the first experimental evidence demonstrating the importance of body size in predicting how large herbivores respond to fire-induced changes in plant quality and quantity.     

Development and optimization of an Agro-BGC ecosystem model for C4 perennial grasses

Extrapolating simulations of bioenergy crop agro-ecosystems beyond data-rich sites requires biophysically accurate ecosystem models and careful estimation of model parameters not available in the literature. To increase biophysical accuracy we added C₄ perennial grass functionality and agricultural practices to the Biome-BGC (BioGeochemical Cycles) ecosystem model. This new model, Agro-BGC, includes enzyme-driven C₄ photosynthesis, individual live and dead leaf, stem, and root carbon and nitrogen pools, separate senescence and litter fall processes, fruit growth, optional annual seeding, flood irrigation, a growing degree day phenology with a killing frost option, and a disturbance handler that simulates nitrogen fertilization, harvest, fire, and incremental irrigation. To obtain spatially generalizable vegetation parameters we used a numerical method to optimize five unavailable parameters for Panicum virgatum (switchgrass) using biomass yield data from three sites: Mead, Nebraska, Rockspring, Pennsylvania, and Mandan, North Dakota. We then verified simulated switchgrass yields at three independent sites in Illinois (IL). Agro-BGC is more accurate than Biome-BGC in representing the physiology and dynamics of C₄ grass and management practices associated with agro-ecosystems. The simulated two-year average mature yields with single-site Rockspring optimization have Root Mean Square Errors (RMSE) of 70, 152, and 162 and biases of 43, −87, 156 g carbon m⁻² for Shabbona, Urbana, and Simpson IL, respectively. The simulated annual yields in June, August, October, December, and February have RMSEs of 114, 390, and 185 and biases of −19, −258, and 147 g carbon m⁻² for Shabbona, Urbana, and Simpson IL, respectively. These RMSE and bias values are all within the largest 90% confidence interval around respective IL site measurements. Twenty-four of twenty-six simulated annual yields with Rockspring optimization are within 95% confidence intervals of Illinois site measurements during the mature fourth and fifth years of growth. Ten of eleven simulated two-year average mature yields with Rockspring optimization are within 65% confidence intervals of Illinois site measurements and the eleventh is within the 95% confidence interval. Rockspring optimized Agro-BGC achieves accuracies comparable to those of two previously published models: Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) and Integrated Farm System Model (IFSM). Agro-BGC suffers from static vegetation parameters that can change seasonally and as plants age. Using mature plant data for optimization mitigates this deficiency. Our results suggest that a multi-site optimization scheme using mature plant data from more sites would be adequate for generating spatially generalizable vegetation parameters for simulating mature bioenergy crop agro-ecosystems with Agro-BGC.