Relationship between metal speciation in soil solution and metal adsorption at the root surface of ryegrass

The total metal content of the soil or total metal concentration in the soil solution is not always a good indicator for metal availability to plants. Therefore, several speciation techniques have been developed that measure a defined fraction of the total metal concentration in the soil solution. In this study the Donnan Membrane Technique (DMT) was used to measure free metal ion concentrations in CaCl(2) extractions (to mimic the soil solution, and to work under standardized conditions) of 10 different soils, whereas diffusive gradients in thin-films (DGT) and scanning chronopotentiometry (SCP) were used to measure the sum of free and labile metal concentrations in the CaCl(2) extracts. The DGT device was also exposed directly to the (wetted) soil (soil-DGT). The metal concentrations measured with the speciation techniques are related to the metal adsorption at the root surface of ryegrass (Lolium perenne L.), to be able to subsequently predict metal uptake. In most cases the metal adsorption related pH-dependently to the metal concentrations measured by DMT, SCP, and DGT in the CaCl(2) extract. However, the relationship between metal adsorption at the root surface and the metal concentrations measured by the soil-DGT was not-or only slightly-pH dependent. The correlations between metal adsorption at the root surface and metal speciation detected by different speciation techniques allow discussion about rate limiting steps in biouptake and the contribution of metal complexes to metal bioavailability.     

To vote or not to vote: abstaining from voting in union representation elections

We conducted two studies addressing abstaining from voting in union representation elections. In Study 1 of a faculty representation election, we showed that compared to voters abstainers possessed less extreme work and union attitudes, believed less in the ability of their vote to affect the election outcomes, and were less involved in the election (e.g., less interested, felt less responsibility to vote). To assess the practical utility of these findings, Study 2 used vignettes in a 2 (traditional bread‐and‐butter issues) × 2 (emerging issues related to fairness) × 2 (voting instrumentality) × 2 (responsibility to vote) experimental manipulation. Results showed that the likelihood of abstaining is reduced when efforts to emphasize the responsibility to vote are presented together with information on both traditional and emerging issues. The two studies show why people abstain from voting in union representation elections, and suggest how abstaining might be reduced. Conceptual implications, practical interventions and research directions raised by the two studies are discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

Testing a post-copulatory pre-zygotic reproductive barrier in a passerine species pair

Sexual selection may drive speciation, but most research focuses on pre-copulatory sexual selection, overlooking post-copulatory processes. Post-copulatory sexual selection in allopatric populations could drive divergence in post-copulatory pre-zygotic (PCPZ) phenotypes, limiting gene flow upon secondary contact. Here, we performed in vitro experiments examining one potential PCPZ barrier between two closely related passerine species, house sparrows (Passer domesticus) and Spanish sparrows (Passer hispaniolensis). In birds, crossing in the vagina may be particularly challenging for sperm, so we tested the effect of female reproductive tract fluids on sperm swimming speed and motility. If a PCPZ barrier exists at this stage of the fertilization process, heterospecific female fluids are predicted to reduce sperm swimming speed or motility relative to conspecific female fluid. We found that house sparrow female fluids affected the two species’ sperm asymmetrically, depending on the control sperm velocity and male species. Overall, however, sperm performed equally in conspecific and heterospecific female fluids, and the species had similar sperm morphology and sperm swimming performance. Low divergence in PCPZ phenotypes between species, perhaps because post-copulatory sexual selection is stabilizing or only moderately strong in these taxa, may be insufficient to cause an overall PCPZ barrier. Reinforcement may be unlikely to drive PCPZ barriers for this species pair, because relatively effective pre-copulatory barriers exist between the species, and because hybrids can be quite successful. Testing the role of PCPZ barriers in birds with more divergent PCPZ phenotypes will improve our understanding of speciation in passerines.     

Gonadal histology and reproductive steroidogenesis in Lithobates pipiens exposed to atrazine

Abstract

Atrazine, an endocrine-disrupting compound and environmental pollutant, can have adverse effects on amphibian reproductive development and function. To determine the effects of atrazine on anuran gonadal development, Lithobates pipiens larvae were exposed from Gosner stage 25 through 1-month post metamorphosis to 0, 2, 20, or 200?μg/L atrazine or estradiol. Exposure to atrazine did not markedly alter tadpole growth, development, gonadal histology, or reproductive steroidogenesis. Testicular ovarian follicles appeared in L. pipiens metamorphs following all treatments, including controls, whereas ovotestes occurred only in positive controls. Testicular ovarian follicles may be a natural ontogenetic occurrence in this species while ovotestes indicate disruption in development. Establishing the normal pattern of reproductive development for anuran species and conducting comparisons in fully sexually differentiated animals is necessary to clarify the influence of endocrine disrupting compounds.     

Energy expenditure and food consumption of foraging Imperial cormorants in Patagonia, Argentina

Energy management during the breeding season is crucial for central place foragers since parents need to feed themselves and their offspring while being spatially and temporally constrained. In this work, we used overall dynamic body acceleration as a measure of activity and also to allude to the foraging energy expenditure of breeding Imperial cormorants Phalacrocorax atriceps. We also analyzed how changes in the time or energy allocated to different activities affected the foraging trip energy expenditure and estimated the daily food requirements of the species. Birds spent 42 % of the total energy flying to and from the feeding areas and 16 % floating at sea. The level of activity underwater was almost 1.5 times higher for females than for males. The most expensive diving phase in terms of rate of energy expenditure was descending though the water column. The total foraging trip energy expenditure was particularly sensitive to variation in the amount of time spent flying. During the breeding season, adult cormorants breeding along the Patagonian coast would consume approximately 10,000 tons of food.     

Low-level sedimentation modifies behaviour in juvenile Haliotis iris and may affect their vulnerability to predation

Sedimentation is an important stressor of coastal ecosystems; yet, there is little research into specific mechanisms by which populations are affected by additional sediment loads resulting from anthropogenic-driven processes. This study explored the potential impact of the proposed disposal of over 7 million m³ of dredge spoil on a nearby fishery for the blackfoot abalone Haliotis iris. The range of sediment deposition predicted by models to occur on reefs inhabited by H. iris as a result of the dispersal of sediment from the disposal site was used to design controlled experiments between July and September 2011 to test the likely effects of sedimentation on: (a) behaviour and mortality of juvenile H. iris and (b) photosynthetic vitality of crustose coralline algae (CCA) that form nursery habitats for H. iris obtained from Brinns Point (45, 40.3′S, 170, 39.4′E). We observed no direct effects on the health or mortality of H. iris juveniles or the photosynthetic vitality of habitat forming CCA. H. iris did, however, avoid sediments by moving from predation refugia beneath cobbles to vertical surfaces on cobble edges significantly more often in sediment treatments compared to sediment-free controls. Deposited sediments were also found to inhibit righting response, key behaviour in allowing H. iris to reattach to the substratum following dislodgement. Results of this study suggest that indirect mortality from reductions in available refugia from predation and inability to recover from dislodgement could be significant. These results highlight the importance of understanding indirect impacts of stressors on key ecological processes in order to predict ecological responses.