A sandy loam soil as a natural control for Pb contamination

The Pb (II) adsorption/desorption mechanism onto a natural sandy loam soil was studied by batch experiments at different pHs (3.0, 4.5, 6.0), at different ionic strength (0, 0.02 and 0.1 M) and with different electrolytes solutions of NaCl, NaAcO and NaNO₃. Pb was strongly adsorbed onto the soil due to the formation of a mix of inner-sphere and outer-sphere complexes. Experimental adsorption data fitted Freundlich and Langmuir isotherms. The desorption results with 0.1 M Mg (NO₃)₂ and 0.1 M NaAcO solutions corroborated the mechanisms proposed. The strong binding of Pb (II) to high affinity sites on soil minerals seems to be responsible for the extent of hysteresis. The sandy loam soil under study thus constitutes a natural control for Pb contamination.     

Environmental Impact Assessment Under the Mackenzie Valley Resource Management Act: Deliberative Democracy in Canada’s North?

We consider the extent to which the Mackenzie Valley Resource Management Act (MVRMA) provides an opportunity for deliberative democracy to emerge within the context of resource management in Canada's North. The focus is on the extent to which the tenets of deliberative democracy are exercised in the environmental assessment (EA) of the Snap Lake diamonds project. Data collection included semi-structured interviews with assessment participants, and a review of documentation surrounding the EA process, and the case study. Results combined four principles of deliberative democracy: generality, autonomy, power neutrality, and ideal role taking. The EA conducted under the MVRMA can serve as a deliberative process, as illustrated by opportunities for dialogue, access to different perspectives, and learning outcomes. However, many of these positive results occurred through nonmandated technical sessions. The absence of participant funding also limits the deliberative potential of the MVRMA.     

Population and seasonal variation in response to prey calls by an eavesdropping bat

The fringe-lipped bat, Trachops cirrhosus, is an eavesdropping predator that hunts frogs and katydids by approaching these preys' sexual advertisement calls. In captivity, bats can rapidly learn to associate novel acoustic stimuli with food rewards. It is unknown how this learning ability is related to foraging behavior in the wild where prey and the calls that identify them vary over space and time. In two bat populations that differ in available prey species (Soberanía, Panama, and La Selva, Costa Rica), we presented wild-caught bats with frog calls, katydid calls, and control stimuli. Bats in Soberanía were significantly more responsive to complex calls and choruses of the túngara frog, Physalaemus pustulosus, than were bats in La Selva. La Selva bats were significantly more responsive to katydid calls (Steirodon sp.) than Soberanía bats. We also examined seasonal variation in bat response to prey cues. Bats were captured in Soberanía in dry and wet seasons and presented with the calls of a dry season breeding frog (Smilisca sila), a wet season breeding frog (P. pustulosus), and four katydid species. Bats captured in the dry season were significantly more responsive to the calls of S. sila than bats captured in the wet season, but there were no seasonal differences in response to the calls of P. pustulosus or the katydid calls. We demonstrate plasticity in the foraging behavior of this eavesdropping predator but also show that response to prey cues is not predicted solely by prey availability.     

Neurological and neuropsychological deterioration in artisanal gold miners from the town of Andacollo,Chile

It is widely known that human exposure to mercury vapor can cause neurological and neuropsychological deterioration. We have investigated if a population of Chilean artisanal gold-mining workers heavily exposed to elemental mercury (Hg⁰) display neurological and neuropsychological impairment. Male volunteers occupationally exposed to Hg⁰ (“gold miners”, n = 35) were recruited and compared with a group of unexposed workers (n = 40). Blood specimens were obtained from both groups for total mercury quantification. Upon neurological examination, 71% of the “gold miners” group showed abnormalities expressed as frontal impairment, tremor, or simultaneously frontal impairment, parkinsonism, and pyramidal syndrome. In contrast, only 16% of the individuals in the control group displayed neurological abnormalities. The “gold miners” group also showed impairment of the neuropsychological performance and the distribution of abnormal scores for almost all the neuropsychological tests applied was significantly higher in this group compared to the control group. Educational level, alcohol intake, and smoking habits did not influence the outcome of the neurological or neuropsychological examinations. Finally, despite that the higher blood mercury concentrations were found in the “gold miners” group, they were not significantly different from the values obtained in the control group.     

Paternity analysis of two male mating tactics in the fiddler crab, Uca mjoebergi

The fiddler crab Uca mjoebergi mates both underground in male-defended burrows and on the surface near female-defended burrows. The reproductive tract of Uca species facilitates last-male precedence, suggesting that males that do not guard-mated females are likely to gain very little paternity if the female re-mates with another male. Here, we test the reproductive success of burrow and surface matings using paternity analysis. We found that 100?% of the females that mated in burrows extruded a clutch of eggs. Furthermore, we show conclusively, for the first time in a fiddler crab species, that last-male sperm precedence results in the majority of the female’s eggs being fertilised by the burrow-mated male. In contrast, surface matings resulted in significantly fewer females extruding eggs (5.6?%). Paternity analysis also revealed that more than half of the clutches from burrow-mated females showed low levels of extra-pair paternity from previous matings. Although multiple matings appear common in U. mjoebergi, burrow-mated males that guard females are guaranteed a successful mating with extremely high rates of assured paternity. Surface matings therefore appear to be an opportunistic tactic that may increase male reproductive success in a highly competitive environment.