Uptake of cadmium by the invasive perennial weeds Ranunculus repens and Geranium robertianum under laboratory conditions

The objective of this study was to compare the accumulation and partitioning of cadmium (Cd) in a fibrous versus a tap root weed, Ranunculus repens and Geranium robertianum respectively. To meet this objective, we compared the accumulation by and the partitioning of Cd in R repens versus G. robertianum grown in soils spiked with 0.015 grams of Cd for a period of three weeks. The rate of Cd uptake was also compared by following the fate of 109Cd within the root, stem and leaf of the two weeds. Prior to Cd exposure, leaf and stem of control R. repens contained significantly greater amounts of Cd as compared to G. robertianum, whereas Cd concentrations in roots of the control plants for the two species were not significantly different (p > 0.05, student's t-test). Post Cd exposure the two species contained similar amounts of Cd in leaf and stem, however, roots of R. repens contained almost two-fold the amounts of Cd as compared to G. robertianum. Comparison of k (h(-1), rate of 109Cd uptake) for stem, leaf and root of the two species indicated that G. robertianum accumulated 109Cd over the first 24-48 h at a faster rate as compared to R. repens. For both species and all three organs, maximum accumulation of 109Cd occurred within the first 24-48 h. Our findings indicate that the fate of Cd within these two species is quite different with the fibrous root of R. repens serving to accumulate and store Cd whereas in G. robertianum, Cd is rapidly taken up and tends to be accumulated within its leaf.     

SIMULATED IMPACTS OF EL NINO/SOUTHERN OSCILLATION ON UNITED STATES WATER RESOURCES1

ABSTRACT: The El Nino/Southern Oscillation (ENSO) phenomena alter global weather patterns with consequences for fresh water supply. ENSO events impact regions and their natural resource sectors around the globe. For example, in 1997 and 1998, a strong El Nino brought warm ocean temperatures, flooding, and record snowfall to the west coast of the United States. Research on ENSO events has improved long range climate predictions, affording the potential to reduce the damage and economic cost of these weather patterns. Here, using the Hydrologic Unit Model for the United States (HUMUS), we simulate the impacts of four types of ENSO states (Neutral, El Niño, La Niña, and strong El Niño) on water resources in the conterminous United States. The simulations show that La Niña conditions increase water yield across much of the country. We find that water yield increases during El Niño years across the south while declining in much of the rest of the country. However, under strong El Niño conditions, regional water yields are much higher than Neutral, especially along the West Coast. Strong El Niño is not simply an amplification of El Niño; it leads to strikingly different patterns of water resource response.     

Workshop report on the extraction of foetal DNA from maternal plasma

Objective Cell free foetal DNA (cff DNA) extracted from maternal plasma is now recognized as a potential source for prenatal diagnosis but the methodology is currently not well standardized. To evaluate different manual and automated DNA extraction methods with a view to developing standards, an International Workshop was performed. Methods Three plasma pools from RhD-negative pregnant women, a DNA standard, real-time-PCR protocol, primers and probes for RHD were sent to 12 laboratories and also to one company (Qiagen, Hilden, Germany). In pre-tests, pool 3 showed a low cff DNA concentration, pool 1 showed a higher concentration and pool 2 an intermediate concentration. Results The QIAamp DSP Virus Kit, the High Pure PCR Template Preparation Kit, an in-house protocol using the QIAamp DNA Blood Mini Kit, the CST genomic DNA purification kit, the Magna Pure LC, the MDx, the M48, the EZ1 and an in-house protocol using magnetic beads for manual and automated extraction were the methods that were able to reliably detect foetal RHD. The best results were obtained with the QIAamp DSP Virus Kit. The QIAamp DNA Blood Mini Kit showed very comparable results in laboratories that followed the manufacturer's protocol and started with ≥ 500 µL plasma. One participant using the QIAamp DNA Blood Midi Kit failed to detect reliably RHD in pool 3. Conclusions This workshop initiated a standardization process for extraction of cff DNA in maternal plasma. The highest yield was obtained by the QIAamp DSP Virus Kit, a result that will be evaluated in more detail in future studies. Copyright © 2007 John Wiley & Sons, Ltd.     

Host selection by a kleptobiotic spider

Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genus Nephila worldwide? Observations following introduction of experimental insect prey of different sizes and weights on to host webs revealed that: (1) small prey are more effectively retained on the web of Nephila clavipes than on the web of another common host, Leucauge venusta. (2) N. clavipes did not consume small prey that accumulated on the web whereas larger, heavier prey were enveloped and stored. (3) We observed clear partitioning of prey items between N. clavipes and Argyrodes spp.; diet selection by Argyrodes did not overlap with that of N. clavipes but closely overlapped with that of L. venusta. (4) L. venusta responds very quickly to prey impact whereas N. clavipes is slower, offering a temporal window of opportunity for Argyrodes foraging. (5) The ability of L. venusta to detect and respond to small items also means that it acts aggressively to Argyrodes spp., whereas N. clavipes does not. Consequently, food-acquisition behaviours of Argyrodes were clearly less risky with N. clavipes compared with L. venusta. We conclude that when a kleptobiotic organism has a choice of various host species, it will opt for the least risky host that presents the highest rate of availability of food items. The fact that Nephila species present such characteristics explains the worldwide association with Argyrodes kleptobiotic spiders.     

Aquatic and terrestrial ecotoxicology considering the soil:water continuum in the Anthropocene context

Environmental Science and Pollution Research -