Effect of two TiO2 nanoparticles on the growth of unicellular green algae using the OECD 201 test guideline: influence of the exposure system

This work aimed at assessing the influence of different exposure systems to perform the commonly used OECD 201 freshwater algal growth inhibition test in the context of nanoparticles hazard assessment. Two distinct TiO₂ nanoparticles were considered and three different exposure systems were investigated: Erlenmeyers flasks and 24-well microplates (both using an orbital shake system), and an alternative system using cylindrical vials and magnetic stirring. All three systems are in accordance with the OECD 201 test guideline recommendations. We concluded that the exposure systems applied to achieve the test can substantially affect the ecotoxicological results and the subsequent calculated ECx. The selected systems influenced both the interaction between algal cells and TiO₂ nanoparticles as well as the growth inhibition recorded. Disparities in ecotoxicity relative to the TiO₂ nanoparticles tested were also observed and are finally discussed.     

Irreplaceable area extends marine conservation hotspot off Tunisia: insights from GPS-tracking Scopoli’s shearwaters from the largest seabird colony in the Mediterranean

Recent meta-analyses identified conservation hotpots at the scale of the Mediterranean, yet those may be crude by lack of detailed information about the spatial ecology of the species involved. Here, we identify an irreplaceable marine area for >95 % of the world population of the Scopoli’s shearwater (Calonectris diomedea), which is endemic to the Mediterranean and breeds on the island of Zembra off Tunis. To this end, we studied the three-dimensional at-sea movements of 50 breeding adults (over a total of 94 foraging trips) in 2012 and 2013, using GPS and temperature–depth recorders. Feathers were also collected on all birds to investigate their trophic status. Despite Zembra being the largest seabird colony in the Mediterranean (141,000 pairs), the per capita home-range of Scopoli’s shearwaters foraging from this colony was not larger than that of birds from much smaller colonies, indicating highly beneficial feeding grounds in the Gulf of Tunis and off Cap Bon. Considering depleted Mediterranean small pelagic fish stocks, supposed to be Scopoli’s shearwater prey base, we therefore speculate that birds may now also largely feed on zooplankton, something which is supported by our stable isotopic analyses. Crucially, shearwater at-sea feeding and resting areas showed very little overlap with a conservation hotspot recently defined on the western side of the Gulf of Tunis using meta-analyses of species distributions relative to anthropogenic threats. We therefore propose a major extension to this conservation hotspot. Our study stresses the importance of detailed biotelemetry studies of marine megafauna movement ecology for refining large-scale conservation schemes such as marine protected area networks.     

Salt-marsh erosion and restoration in relation to flood protection on the Wadden Sea barrier island Terschelling

This paper explores the impact of erosion and restoration measures on habitat development and on wave damping by a small salt marsh nestled alongside a dike on the Wadden island of Terschelling. The aim is to advance knowledge about the benefits and possible side-effects of salt-marsh restoration. Analysis of a time series of aerial photographs from 1944 to 2010 indicates that the salt marsh decreased steadily in size after maintenance of accretion works was terminated. In the western part of the marsh, which is accessible to sheep, vegetation is low (5–15 cm) and dominated by Salicornia europaea and by Spartina anglica. In the most intensively grazed parts, vegetation is very scarce. The eastern, inaccessible part of the salt marsh is covered by dense patches of the shrubby perennial Atriplex portulacoides and Spartina anglica (15–25 cm in height). SWAN wave models show that wave height at this location is significantly affected by the areal extent of the salt marsh as well as by the vegetation. High or dense vegetation are in the models nearly as effective in damping waves (with an initial height of 0.15 and 0.5 m) as widening the salt-marsh area by 350 m. A low density of low plants, as observed in the grazed part of the marsh, has almost no wave-damping effect. Even under conditions of sea level rise, a broader salt marsh vegetated with high plants significantly affects modelled wave height. Therefore, salt-marsh restoration is an adaptation measure worth exploring, though an array of effect types must be considered.     

Employee responses to employment‐relationship practices: The role of psychological empowerment and traditionality

In studying the effect of employment‐relationship practices on employees, research has largely ignored individual differences, both cross‐culturally and within cultures. In this study, the authors examine the moderating effect of middle managers' traditionality, a within‐culture value orientation regarding submission to authority and endorsement of hierarchical role relationships, on their responses to an organization's employee–organization relationship practices. Based on social learning and social exchange theories, the authors expect the more traditional middle managers to respond less positively in terms of their performance and commitment to high levels of expected contributions and the associated psychological empowerment but respond more positively to high levels of offered inducements. Using a sample of 535 middle managers from 40 companies in China, the authors find support for all hypotheses except the moderating effect of traditionality on the relationship between offered inducements and performance. Additional analysis reveals that less‐traditional managers responded to economic rewards (but not developmental rewards) with higher job performance. The paper concludes with a discussion of implications for research and the practice of employment relationships. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental evidence for the effects of task repetitiveness on mental strain and objective work performance

People frequently have to work in high repetitive jobs. Previous research has focused exclusively on the effects of task repetitiveness on well‐being, while neglecting effects on work performance. In the present study, we aimed to fill this void by conducting two workplace simulations with experimental manipulations of task repetitiveness. Participants worked for about 5 hours at either a computer workstation, compiling computer hardware packages according to customer requests (Experiment 1, N = 160), or at an assembly line, piecing together equipment sets for furniture (Experiment 2, N = 213). Both experiments provide consistent evidence that high repetitiveness has a detrimental effect on well‐being, whereas work performance increases under conditions of high repetitiveness. On a practical level, our study hence shows that high task repetitiveness is a double‐edged sword for both employees and organizations. On a conceptual level, our findings emphasize the necessity to account for both mental strain and work performance when examining the effects of task repetitiveness. Copyright © 2014 John Wiley & Sons, Ltd.     

Physiological tolerance predicts species composition at different scales in a barnacle guild

This study examined how the species composition of an intertidal barnacle guild varied according to physical gradients in the environment at small scales governed by microclimates, medium scales of wave exposure and large scales of latitude. Barnacle distributions at small and medium scales were sampled in Ireland between 51°29′ and 52°44′N and 6°50′ and 10°08′W. Sampling on European shores spanned ~18° latitude from 37°05′ to 55°16′N. Barnacle surveys mainly took place in 2003–2004. An index of wave fetch was calculated along the wave exposure gradient using a digital coastline-based model that was supported by a biological exposure scale. A ‘dryness’ index was defined according to mean monthly wind speed, fetch along the average wind direction and mean monthly air or sea surface temperatures for 2 years (January 2001–December 2002) which is the period when the most recent adults in the barnacle community would have settled and grown to adulthood. The proportion of the dry-loving barnacle Chthamalus montagui Southward increased within the barnacle guild at all scales as the habitat became warmer and drier. Barnacle densities were high in all habitats, mean densities ranged from a minimum of 4.16 cm⁻² on moderately exposed shores to a maximum of 6.27 cm⁻² in sunlit or south-facing microclimates. Percentage cover of barnacles across the gradient of latitudes was usually >70%. The results suggest that the distribution and abundance of interacting barnacle species on European coasts is strongly controlled by abiotic factors, most likely temperature and desiccation.     

Sperm storage reflects within- and extra-pair mating opportunities in a cooperatively breeding bird

In passerine birds, storage and maturation of sperm takes place in the cloacal protuberance (CP), an external swelling of the reproductive organ. The considerable variation in CP size among species is presumed to be a consequence of varying levels of sperm-competition, but whether individual variation in CP size within a species also reflects sperm competition is not well established. Here, we study temporal variation in male CP size in relation to within-pair and extra-pair mating opportunities and cuckoldry risk in purple-crowned fairy-wrens Malurus coronatus. This is a socially monogamous cooperatively breeding passerine that can breed year-round and has low levels of extra-pair paternity (in 6?% of broods). We show that male CP size sharply increased a few weeks before, and rapidly regressed after his partner laid eggs, consistent with a cost of its maintenance and/or sperm production. Surprisingly, despite low levels of extra-pair paternity, CP size of non-breeding and pre-breeding males was positively correlated with the number of breeding females in the population, suggesting that CP size is sensitive to extra-pair mating opportunities. However, CP sizes do not seem to reflect cuckoldry risk: CP size of dominant males was unaffected by the presence of a subordinate that was unrelated to the dominant female, although those subordinates occasionally sire offspring, and had a larger CP than subordinates living with their mother. Our results suggest that, even in a species with low levels of extra-pair paternity, individual investment in sperm storage reflects both within-pair and, albeit to lesser extent, extra-pair mating opportunities.     

The three-dimensional prey field of the northern krill, Meganyctiphanes norvegica, and the escape responses of their copepod prey

In the north Atlantic, Meganyctiphanes norvegica feeds predominantly on copepods, including Calanus spp. To quantify its perceptual field for prey, and the sensory systems underlying prey detection, the responses of tethered krill to free-swimming Calanus spp. were observed in 3D using silhouette video imaging. An attack–which occurred despite the krill’s being tethered—was characterized by a pronounced movement of the krill’s antennae towards the target, followed by a propulsion and opening of the feeding basket. Frequency distributions of prey detection distances were significantly different in the light vs. the dark, with median values of 26.5 mm and 19.5 mm, respectively. There were no significant differences in the angles at which prey were detected by krill (relative to the predator’s longitudinal body axis) in the light vs. the dark. Prey detections were symmetrically distributed on either side of the predator, in both light and dark. However, significant asymmetry was found in the dorsal–ventral direction with 80% of the prey detections located below the midline of the krill’s body axis and, given the placement and orientation of the compound eyes, presumably outside its visual field of view. This indicates that, at least under these conditions, vision was not the main sensory modality involved in the detection of active prey by M. norvegica. However, under some circumstances, vision may provide supplemental information. Avoidance responses of copepod prey were nearly twice the velocity of their nominal background swimming speed (153 ± 48 and 85 ± 75 mm s⁻¹, respectively), on average taking them 43 ± 16 mm away from the predator. This is far beyond the krill’s perceptual range, suggesting that the escape reaction provides an effective deterrent to predation (although perhaps less so for free-swimming krill). This information can be used to parameterize models that assess the role of krill as predators in marine ecosystems.     

Female chacma baboons form strong, equitable, and enduring social bonds

Analyses of the pattern of associations, social interactions, coalitions, and aggression among chacma baboons (Papio hamadryas ursinus) in the Okavango Delta of Botswana over a 16-year period indicate that adult females form close, equitable, supportive, and enduring social relationships. They show strong and stable preferences for close kin, particularly their own mothers and daughters. Females also form strong attachments to unrelated females who are close to their own age and who are likely to be paternal half-sisters. Although absolute rates of aggression among kin are as high as rates of aggression among nonkin, females are more tolerant of close relatives than they are of others with whom they have comparable amounts of contact. These findings complement previous work which indicates that the strength of social bonds enhances the fitness of females in this population and support findings about the structure and function of social bonds in other primate groups.