Why should I be generous when I have valued and accessible alternatives? Alternative exchange partners and OCB

An Erratum has been published for this article in Journal of Organizational Behavior 26(7) 2005, 873. Previous research on the relationship between alternative employment opportunities and cooperation has neglected the distinction between evaluations and restrictions. Thus, one cannot analyze the relationship between attractiveness of alternative employment opportunities and organizational citizenship behaviors (OCB) under different levels of perceived ease of finding alternative employment. In a pilot study with N = 149 German employees, we confirm the proposed distinction with confirmatory factor analyses. Based on power‐dependence theory and rational choice models, we predict that under high ease the relationship between attractiveness and OCB should be more strongly negative than under conditions of low ease. In addition, we hypothesize that the interaction between attractiveness and ease should be greater for OCB than for task performance because task performance is exchanged in a relationship with an enforceable, binding contract, while OCB is voluntarily. Results from moderated multiple regression analysis on N = 86 German professional–supervisor dyads support our prediction for a negative relationship between attractiveness and OCB under high ease. Under low ease, we find a positive relationship between attractiveness and OCB. Moreover, there was no relationship with the interaction and task performance. Implications of the findings both for extra‐role and job mobility theory formation and research are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Predicting the sensitivity of fishes to dioxin-like compounds: possible role of the aryl hydrocarbon receptor (AhR) ligand binding domain

Dioxin-like compounds are chronically toxic to most vertebrates. However, dramatic differences in sensitivity to these chemicals exist both within and among vertebrate classes. A recent study found that in birds, critical amino acid residues in the aryl hydrocarbon receptor (AhR) ligand binding domain are predictive of sensitivity to dioxin-like compounds in a range of species. It is currently unclear whether similar predictive relationships exist for fishes, a group of animals at risk of exposure to dioxin-like compounds. Effects of dioxin-like compounds are mediated through the AhR in fishes and birds. However, AhR dynamics are more complex among fishes. Fishes possess AhRs that can be grouped within at least three distinct clades (AhR1, AhR2, AhR3) with each clade possibly containing multiple isoforms. AhR2 has been shown to be the active form in most teleosts, with AhR1 not binding dioxin-like compounds. The role of AhR3 in dioxin-like toxicity has not been established to date and this clade is only known to be expressed in some cartilaginous fishes. Furthermore, multiple mechanisms of sensitivity to dioxin-like compounds that are not relevant in birds could exist among fishes. Although, at this time, deficiencies exist for the development of such a predictive relationship for application to fishes, successfully establishing such relationships would offer a substantial improvement in assessment of risks of dioxin-like compounds for this class of vertebrates. Elucidation of such relationships would provide a mechanistic foundation for extrapolation among species to allow the identification of the most sensitive fishes, with the ultimate goal of the prediction of risk posed to endangered species that are not easily studied.     

Effectiveness of the strategies to combat land degradation and drought

This paper focuses on the determination of the most effective set of mitigation and adaptation strategies applied to combat land degradation and drought in a latitudinal gradient. This study was carried out in Chile, in a latitude gradient between 17° 30′S and 36° 33′S. The northern regions are mostly formed by desert and dry land, which can be considered as marginal areas for agriculture. On the other hand, the area formed by the southern regions has an industrialized agriculture where an increased use of technology takes place and where the climate and water availability are optimal for the development of agriculture. The period considered in this study was between 2000 and 2007. We calculated an Investment Effectiveness Index. Afterwards, and in order to assess the effectiveness of the financial support, we performed multiple regressions (P?≤?0.05), where the Index was considered as the independent variable, and the annual difference of the area affected by a high risk of desertification was considered as the dependent variable. Our findings suggest that the effectiveness of the different set of the strategies applied to fight against desertification and drought varies in a latitudinal gradient. Thus, in arid and hyper arid areas the promotion of modern irrigation systems seems to be effective in combating desertification, while in Mediterranean climates the reforestation strategies seem to play an important role. Our results suggest that in areas heavily degraded by overgrazing, the most effective strategies are those oriented to obtain a permanent vegetation cover on degraded soils.     

Valuing power plant flexibility with CCS: the case of post-combustion capture retrofits

An important development in recent years has been increased interest in retrofitting CO₂ capture at existing power plants. In parallel, it has also been suggested that flexible operation of power plants with CO₂ capture could be important in at least some jurisdictions. It is likely that retrofitted power plants could have significant ??built-in?? flexibility, but this potential is often not considered in studies of the economic performance of power plants with CO₂ capture. This paper makes a contribution to filling this gap by developing methods for first order screening analysis of flexible operation of power plants with CO₂ capture and applying them to the case study example of an appropriately integrated retrofit of post-combustion capture at a coal-fired power plant. The quantitative analysis suggests that rich solvent storage could be an attractive option on a short-run basis for some fuel, CO₂ and electricity price combinations. Results from first order analysis can then be used to determine which operating modes should (and shouldn??t) be included in further, more detailed design studies.     

Local extinction of a foundation species in a hypoxic estuary: integrating individuals to ecosystem

We integrated across individual, population, community, and ecosystem levels to understand the impact of environmental stress by tracking the foundation species Mytilus edulis in the hypoxic estuary Narragansett Bay, Rhode Island, USA. Our initial surveys revealed that the mussels occurred in nine extensive (2-28 ha) dense (814-9943 individuals/m2) subtidal reefs that attracted a diverse suite of predators (sea stars, crabs, gastropods). Hypoxia occurred in the summer of 2001, and a mussel transplant experiment revealed overall reduced growth rates of individuals, and higher mortality rates among larger mussels. At the population level, large decreases in densities and cover of mussels were correlated with dissolved oxygen concentrations, leading to extinction at one site and reductions of over an order of magnitude at others. Within one year, seven of the eight remaining populations were edged to extinction, and the previously extinct population was recolonized. At the community level, a predator exclusion experiment indicated that predation was an unimportant source of mussel mortality during the hypoxic period, in part due to the emigration of sea stars, as predicted by the Consumer Stress Model. However, mussels were too intolerant to hypoxia to have a net benefit from the predation refuge. The seasonal (summer) occurrence of hypoxia allowed sea stars to return following a lag, as predicted by a stress return time model, and the resumption of predation contributed to the subsequent extinction of mussel populations. At the ecosystem level, the initial filtration rate of the mussel reefs was estimated at 134.6 x 10(6) m3/d, equivalent to filtering the volume of the bay 1.3 times during the 26-d average residence time. That function was reduced by >75% following hypoxia. The effect of hypoxia on each level of organization had consequences at others. For example, size-specific mortality and decreased growth of individuals, and reduced filtration capacity of reefs, indicated a loss of the ability of mussels to entrain planktonic productivity and potential to control future eutrophication and hypoxia. Our study quantified patterns of loss and identified pathways within an integrative framework of feedbacks, summarized in a conceptual model that is applicable to similar foundation species subjected to environmental stress.     

Sexual dimorphism and the mating ecology of polar bears (Ursus maritimus) at Svalbard

We assessed the role of size, mass, and age in mating and non-mating polar bears (Ursus maritimus) at Svalbard, Norway, during the spring breeding season. The ratio of male to female mass, in male-female pairs, ranged from 1.00 to 3.02 ([`(x)] = 1.99 \overline x = 1.99 ) indicating that mating males were larger than mating females but with substantial variation. Paired males were older than unpaired males and male mass was related to age. However, males paired with females were not significantly different in body mass from those males caught alone. Wounds and scars resulting from fights between males began at about 6 years of age and peaked at about 17 and 20 years of age, respectively. The frequency of broken canines in males, presumably due to increased male-male conflicts, increased with age but showed little increase in females. The wide range of male size in male-female pairs and the age-related signs of injury suggest that male polar bears engage in both scramble competition and contest competition for access to breeding females. The mating system of polar bears is variable but is best described as female defense polygyny or serial monogamy.     

Interaction of phenanthrene and its primary metabolite (1-hydroxy-2-naphthoic acid) with estuarine sediments and humic fractions

Experiments were conducted to compare the sorption and desorption of phenanthrene and its primary degradation product, 1-hydroxy-2-naphthoic acid (HNA), in estuarine sediment, humic acid (HA) and humin. Ionic composition, ionic strength (0.4 M) and pH (7.6) were employed to mimic native estuarine pore water at the sediment-water interface. Sorption to whole sediment and organic matter (OM) fractions was significantly lower for HNA than for phenanthrene. Whereas HNA did not sorb to HA, uptake to sediment and humin was observed, suggesting that HNA does not bind directly to OM. Phenanthrene uptake was characterized by hysteretic behavior and exhibited slow desorption. In contrast, HNA initially was more readily desorbed from sediment and humic fractions, but a significant fraction was not recovered in repeated desorption runs. The lower sorption of HNA reflects its greater polarity and water solubility, but the consistent retention of a non-desorbing fraction suggests strong binding and/or chemical transformation reactions may be important. It was postulated that abiotic transformation of HNA may occur in estuarine sediments, in part due to the presence of redox active minerals (Fe(III) and Mn(IV) oxides). The presence of Fe and Mn solids in the estuarine sediment was verified by sequential extraction and studies were then conducted to investigate the transformation of HNA in the presence of synthetic goethite (alpha-FeOOH) and birnessite (delta-MnO2) as model solids. Reaction with birnessite led to transformation of all HNA in solution within 24 h and resulted in the formation of partial oxidation products (POPs). Following reaction with goethite, HNA was present in solution and POPs were observed in the weakly bound fraction. This study indicates that degradation products of polycyclic aromatic hydrocarbons (PAHs) may have distinctly different sorption affinities and reactivities toward environmental surfaces than their parent compounds.     

Bioeconomic models of marine recreational fishing

The theory of recreational fishing is developed and conditions are derived for optimal management policy, with special attention given to functional relationships that must be empirically verified. Determinants of the optimal allocation between commercial and recreational fishing effort are derived. The theory is extended to include selected peculiar features of recreational fishing: Some anglers sell their catch; a small proportion of the fishing population accounts for a large proportion of the catch; and anglers throw back a fraction of what they catch. Optimal policies are derived under these more realistic conditions.