POM in macro-/meiofaunal food webs associated with three flow regimes at deep-sea hydrothermal vents on Axial Volcano,Juan de Fuca Ridge

Deep-sea hydrothermal vent ecosystems host both symbiotic and non-symbiotic invertebrates. The non-symbiotic vent fauna is generally assumed to rely on free-living chemoautotrophic bacteria as their main food source but other sources such as detritus have recently been suggested to be a part of the invertebrate diets. Little is known about how food availability influences the distribution of vent organisms on a small scale. In addition, the feeding ecology and role of small, often numerically dominant invertebrates, the meiofauna is poorly understood at vents. In this study, we used stable carbon and nitrogen isotopic analysis to investigate the role of particulate detritus in the diets of macro- and meiobenthic invertebrates within three vent assemblages at Axial Volcano, Juan de Fuca Ridge, and Northeast Pacific. Particulate organic matter of a detrital origin became more important in the diet of invertebrates in assemblages typically associated with low-hydrothermal flow intensities. Meiobenthic species occupied several different feeding guilds and trophic levels in the assemblages investigated. We conclude that small-scale spatial variability in food sources is an important feature of vent food webs and that spatial patterns observed here and elsewhere are shaped by variations in hydrothermal discharge.     

Leadership, psychological capital and safety research: Conceptual issues and future research questions

In this theory-driven literature review we examine how leadership and emerging research in positive organizational behaviour (POB) may inform our understanding of human mechanisms that affect safety outcomes. According to authentic leadership theory, leader self-awareness and self-regulation processes are vital mechanisms in the leader-follower exchange. From emerging research on authentic leadership, we propose that production management values, attitudes, and behaviour are linked to safety climate and safety outcomes in safety critical organizations (SCOs). According to recent developments in management theory, “psychological capital” is comprised of four distinct aspects that can be linked to desirable organizational outcomes and sustained high quality performance in individual workers. From this we offer a research model and five research propositions implicating that authentic leadership directly affects safety outcomes via promoting positive safety climate perceptions. Furthermore, we propose a second path where psychological capital mediates the relationship between authentic leadership, safety climate and safety outcomes in SCOs.     

Between a rock and a hard place: Accident and near-miss reporting on offshore service vessels

Reporting accidents and near misses is an important aspect of safety management. This study explores reporting in contract work, exemplified by offshore service vessels, and the associations with external and internal organisational factors. The empirical foundation for the study is a questionnaire survey (N = 1108). Reporting was negatively related to high efficiency demands from external actors and low quality of feedback to the reporting community. These factors were more strongly related to reporting than internal factors within the safety climate construct. Short-term contract engagement was also negatively associated with reporting. The results could reflect the organisational complexity that characterises much contract work. The study implies that attempts to increase the level of reporting in contract work should not be limited to focusing on internal organisational factors. Framework conditions and signals from external actors regarding the actual priority accorded to safety should also be considered.     

Antagonistic effect of natural habitat conversion on community adjustment to climate warming in nonbreeding waterbirds

Although the impacts of climate and land-use changes on biodiversity have been widely documented, their joint effects remain poorly understood. We evaluated how nonbreeding waterbird communities adjust to climate warming along a gradient of land-use change. Using midwinter waterbird counts (132 species) at 164 major nonbreeding sites in 22 Mediterranean countries, we assessed the changes in species composition from 1991 to 2010, relative to thermal niche position and breadth, in response to regional and local winter temperature anomalies and conversion of natural habitats. We observed a low-level, nonsignificant community adjustment to the temperature increase where natural habitat conversion occurred. At the sites affected by natural habitat conversion, the relative increase of warm-dwelling species in response to climate warming was 6 times lower and the relative species decline was 3 times higher than in the sites without natural habitat conversion. We found no evidence of community adjustment to climate warming when natural habitat conversion was >5% over 15 years. This strong negative effect suggests an antagonistic interaction between climate warming and habitat change. These results underline the importance of habitat conservation in community adjustment to climate warming.     

Roles of survival and dispersal in reintroduction success of Griffon vulture (Gyps fulvus).

The success of reintroduction programs greatly depends on the amount of mortality and dispersal of the released individuals. Although local environmental pressures are likely to play an important role in these processes, they have rarely been investigated because of the lack of spatial replicates of reintroduction. In the present study, we analyzed a 25-year data set encompassing 272 individuals released in five reintroduction programs of Griffon Vultures (Gyps fulvus) in France to examine the respective roles of survival and dispersal in program successes and failures. We use recent developments in multi-strata capture-recapture models to take into account tag loss in survival estimates and to consider and estimate dispersal among release areas. We also examined the effects of sex, age, time, area, and release status on survival, and we tested whether dispersal patterns among release areas were consistent with habitat selection theories. Results indicated that the survival of released adults was reduced during the first year after release, with no difference between sexes. Taking into account local observations only, we found that early survival rates varied across sites. However when we distinguished dispersal from mortality, early survival rates became equal across release sites. It thus appears that among reintroduction programs difference in failure and success was due to differential dispersal among release sites. We revealed asymmetrical patterns of dispersal due to conspecific attraction: dispersers selected the closest and the largest population. We showed that mortality can be homogeneous from one program to another while, on the contrary, dispersal is highly dependent on the matrix of established populations. Dispersal behavior is thus of major interest for metapopulation restoration and should be taken into account in planning reintroduction designs.     

A two-dimensional simulation model of phosphorus uptake including crop growth and P-response

Modelling nutrient uptake by crops implies considering and integrating the processes controlling the soil nutrient supply, the uptake by the root system and relationships between the crop growth response and the amount of nutrient absorbed. We developed a model that integrates both dynamics of maize growth and phosphorus (P) uptake. The crop part of the model was derived from Monteith's model. A complete regulation of P-uptake by the roots according to crop P-demand and soil P-supply was assumed. The soil P-supply to the roots was calculated using a diffusion equation and assuming that roots behave as zero-sinks. The actual P-uptake and crop growth were calculated at each time step by comparing phosphate and carbohydrate supply–demand ratios. Model calculations for P-uptake and crop growth were compared to field measurements on a long term P-fertilization trial. Three P-fertilization regimes (no P-fertilization, 42.8 kg P ha⁻¹ year⁻¹ and 94.3 kg P ha⁻¹ year⁻¹) have led to a range of P-supply. Our model correctly simulated both the crop development and growth for all P-treatments. P-uptake was correctly predicted for the two non-limiting P-treatments. Nevertheless, for the limiting P-treatment, P-uptake was correctly predicted during the early period of growth but it was underestimated at the last sampling date (61 day after sowing). Several arguments for under-prediction were considered. However, most of them cannot explain the observed magnitude in discrepancy. The most likely reason might be the fact that biomass allocation between shoot and root must be modelled more precisely. Despite this mismatch, the model appears to provide realistic simulations of the soil–plant dynamic of P in field conditions.     

Transformational leadership,psychological empowerment,and the moderating role of mechanistic–organic contexts

The current study examines the empowering effects of transformational leaders and the extent to which these effects differ across mechanistic–organic organizational contexts. Psychological empowerment is hypothesized to provide a comprehensive motivational mechanism explaining the relationships between transformational leadership and employee job‐related behaviors. In addition, the relationships between transformational leadership, employee psychological empowerment, and job‐related behaviors are hypothesized to be stronger in organizations with more organic as opposed to mechanistic structures. Results based on a cross‐organizational sample of employees and their immediate supervisors provide support for the hypothesized relationships. Psychological empowerment mediated relationships between transformational leadership and employee task performance and organizational citizenship behaviors. The mediating role of psychological empowerment was then found to be conditional upon mechanistic–organic contexts. More specifically, organic structures enhanced, whereas mechanistic structures constrained, the empowering influence of transformational leaders. In highly mechanistic contexts, the indirect effects were no longer statistically significant. Implications for theory, research, and organizational management are discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Modeling atmospheric mercury deposition in the vicinity of power plants

Two mathematical models of the atmospheric fate and transport of mercury (Hg), an Eulerian grid-based model and a Gaussian plume model, are used to calculate the atmospheric deposition of Hg in the vicinity (i.e., within 50 km) of five coal-fired power plants. The former is applied using two different horizontal resolutions: coarse (84 km) and fine (16.7 km). More than 96% of the power plant Hg emissions are calculated with the plume model to be transported beyond 50 km from the plants. The grid-based model predicts a lower fraction to be transported beyond 50 km: >91% with a coarse resolution and >95% with a fine resolution. The contribution of the power plant emissions to total Hg deposition within a radius of 50 km from the plants is calculated to be <8% with the plume model, <14% with the Eulerian model with a coarse resolution, and <10% with the Eulerian model with a fine resolution. The Eulerian grid-based model predicts greater local impacts than the plume model because of artificially enhanced vertical dispersion; the former predicts about twice as much Hg deposition as the latter when the area considered is commensurate with the resolution of the grid-based model. If one compares the local impacts for an area that is significantly less than the grid-based model resolution, then the grid-based model may predict lower local deposition than the plume model, because two compensating errors affect the results obtained with the grid-based model: initial dilution of the power plant emissions within one or more grid cells and enhanced vertical mixing to the ground.     

Air quality modeling of hazardous pollutants: current status and future directions

The current requirements and status of air quality modeling of hazardous pollutants are reviewed. Many applications require the ability to predict the local impacts from industrial sources or large roadways as needed for community health characterization and evaluating environmental justice concerns. Such local-scale modeling assessments can be performed by using Gaussian dispersion models. However, these models have a limited ability to handle chemical transformations. A new generation of Eulerian grid-based models is now capable of comprehensively treating transport and chemical transformations of air toxics. However, they typically have coarse spatial resolution, and their computational requirements increase dramatically with finer spatial resolution. The authors present and discuss possible advanced approaches that can combine the grid-based models with local-scale information.     

Humic substances

GOALS, SCOPE AND BACKGROUND: Changing environmental conditions and handling stress are well known to cause chronic or acute stress situations in fish with subsequent infections. These requires a therapy by means of antibiotics and chemicals. In contrast to the huge number of pathogens, only a few substances are permitted for application as therapeutics in German aquaculture. Hence, there emerges an urgent need for highly effective and residueless alternatives. MAIN FEATURES: The prophylactic stimulation and training of the defense system of fish by alternative approaches becomes increasingly necessary. One approach is the application of dissolved humic substances (HS) of natural or artificial origin. For example, there exist several reports on the positive effect of HS to fishes. These effects shall be considered in detail. Furthermore, the impact of HS on the constitution of parasites and pathogens will be displayed. The reports on this issue are diverse, if not inconsistent. We try to shed some light on these discrepancies. The last aspect covered by this review is the outdated paradigm that calcium ions act as antidotes. In the presence of HS, even the opposite effect may occur. APPROACH: To overcome old paradigms on HS and their potential interactions with fish and fish parasites, we reviewed recent international literature, as well as 'grey' literature. We also include results from own former and ongoing studies. RESULTS AND DISCUSSION: HS are able to increase the physiological condition of the individuals and to reduce adverse physiological and histological consequences caused by stress; the mechanism behind remains obscure. HS detoxify heavy metals and organic pollutants. Damages caused by several fish pathogens, such as bacteria and parasites, can be repaired more quickly in the presence of HS. Some parasites--mainly fungi--appear to be directly affected by HS. Comparing the fungicidal effects of HS from various sources, evidence is increasing that the aliphatic moiety may be the effective structures. However, further research is necessary to relate more physiological and anti-pathogenic effects to the chemical characteristics of HS. CONCLUSIONS: HS are not real alternatives to strong traditional therapeutics. However, they show different advantages in repairing secondary, stress induced damages in fish. The ecophysiological relevance of HS in either aquatic systems or aquaculture is getting conspicuously. PERSPECTIVES: The lack of therapeutic and antiparasitic substances in aquaculture requires new strategies and ways of thinking. The search for alternatives to the 'traditional' chemical therapeutics calls for the intensive research. Inevitably, this search will lead to an intensive contemplation on HS as 'health promoting substances' and/or even therapeutics. Basic research is needed to detect the functional groups of the HS responsible for the effects observed. Health promoting effects of first investigations made in vitro to affect pathogens via application of HS and several field studies with HS raises hopes for a broader utilisation of HS to reduce stress consequences in fish and fish pathogens residuelessly.