Nest association in fishes: evidence for mutualism

Nest association, or the habit of spawning in the nest of another species, is a widespread reproductive strategy among North American fishes, especially minnows. The hosts of nest associates include sunfishes and nest-building minnows. Previous experiments demonstrated that nest associates benefited from the parental care of hosts. The purpose of this study was to determine the effect of nest associates on hosts, and thereby characterize the relationship as parasitic, mutualistic or commensal. Since hosts with associates had higher reproductive success than those without associates in this experiment, I characterize nest association as a mutualistic relationship, at least in some systems. The dilution effect is the proposed mechanism responsible for the higher reproductive success of hosts with associates.     

In vitro dissolution studies of uranium bearing material in simulated lung fluid

Inhaled uranium (U) bearing material will partially dissolve in the fluid lining of the lung, followed by a combination of retention, re-distribution, and excretion of the U. The rate of dissolution influences the retention time at the site of deposition, and the extent to which the material is available for re-distribution to other tissues. The consequential radiation dose is dependent upon the material distribution in the body and the exposure time to various tissues. The International Commission on Radiological Protection, ICRP 66 [International Commission on Radiological Protection (ICRP), 1994. Human Respiratory Tract Model for Radiological Protection. ICRP Publication 66] recommends the use of experimentally determined solubility coefficients in dose modelling. Material specific absorption parameters allow for better dose estimation than using ICRP default values for F (fast), M (moderate) and S (slow) classifications of U compounds. In vitro dissolution tests were carried out on U material collected from two U mines located in Australia. A static technique was designed in which particle samples were sandwiched between two 0.1-mum pore size membrane filters. The filter sandwich was exposed to a solvent (simulated lung fluid) for selected time intervals, at controlled test conditions for temperature and pH. The collected solution was analysed for U concentration using ICP-MS. The resulting dissolution curves were fitted with a double or triple exponential equation to determine the dissolution coefficients.     

Variable Responses of Soybeans to Mixtures of Ozone and Sulfur Dioxide

Foliar injury and shoot fresh weight responses of soybeans (Glycine max L.) ‘Lee 68’ and ‘Dare’ exposed to mixtures of ozone (O₃) and sulfur dioxide (SO₂) were greater than additive (synergistic), less than additive (antagonistic), or additive. The result depended on the concentrations of O₃ and SO₂, the exposure duration, and the amount of injury caused by each gas singly. Synergism usually occurred when injury from O₃ or SO₂ singly was slight to moderate. Antagonism usually occurred when injury from either gas singly was severe. In many cases of antagonism, the injury and fresh weight effects of the mixture were less than those from SO₂ alone, suggesting that O₃ can sometimes protect soybeans from SO₂.     

Hydrothermal oxidation of waste lipids, protein, and starch from New Zealand meat- and vegetable-processing plants.

Disposal of organic waste materials from the meat- and vegetable-processing industries historically has been undertaken by dumping, drying followed by combustion, or biological oxidation. As a result of higher intensity processing rates and increasingly stringent legislation, these are no longer economical. Hydrothermal oxidation, also referred to as "wet" oxidation, has been used to lower the chemical and biological oxygen demand of waste samples from the above two industries. The starch-based wastes were readily oxidized without a catalyst. For the lipid and protein-based wastes, the use of copper calcium silicate and nitrate catalysts provided a significant reduction in oxygen demand at 230 degrees C.     

Is remaining indoors an effective way of reducing exposure to fine particulate matter during biomass burning events?

Bushfires, prescribed burns, and residential wood burning are significant sources of fine particles (aerodynamic diameter <2.5 μm; PM_2.5) affecting the health and well-being of many communities. Despite the lack of evidence, a common public health recommendation is to remain indoors, assuming that the home provides a protective barrier against ambient PM_2.5. The study aimed to assess to what extent houses provide protection against peak concentrations of outdoor PM_2.5 and whether remaining indoors is an effective way of reducing exposure to PM_2.5. The effectiveness of this strategy was evaluated by conducting simultaneous week-long indoor and outdoor measurements of PM_2.5 at 21 residences in regional areas of Victoria, Australia. During smoke plume events, remaining indoors protected residents from peak outdoor PM_2.5 concentrations, but the level of protection was highly variable, ranging from 12% to 76%. Housing stock (e.g., age of the house) and ventilation (e.g., having windows/doors open or closed) played a significant role in the infiltration of outdoor PM_2.5 indoors. The results also showed that leaving windows and doors closed once the smoke plume abates trapped PM_2.5 indoors and increased indoor exposure to PM_2.5. Furthermore, for approximately 50% of households, indoor sources such as cooking activities, smoking, and burning candles or incense contributed significantly to indoor PM_2.5.

Implications: Smoke from biomass burning sources can significantly impact on communities. Remaining indoors with windows and doors closed is a common recommendation by health authorities to minimize exposures to peak concentrations of fine particles during smoke plume events. Findings from this study have shown that the protection from fine particles in biomass burning smoke is highly variable among houses, with information on housing age and ventilation status providing an approximate assessment on the protection of a house. Leaving windows closed once a smoke plume abates traps particles indoors and increases exposures.     

Cadmium in cereal grain and herbage from long-term experimental plots at Rothamsted, UK

Crop samples harvested and stored from three long-term agricultural experiments started in the 1840-1850s at Rothamsted Experimental Station (UK) have been analysed recently for Cd. Increased Cd burden in the soils of the experiments, which have had a range of treatments, originates mainly from atmospheric deposition. Soils treated with farmyard manure (FYM) or, in some cases, applications of phosphate fertilisers, have increased Cd levels. Herbage, wheat and barley grain from the three experiments were analysed by neutron activation analysis (NAA) and graphite furnace atomic absorption spectrometry (GFAAS). Samples were bulked for groups of years between 1860 and 1986, from variously treated plots in each experiment (control or 'nil' treatment, P-fertilised, FYM-amended, NPK-fertilised-limed and unlimed). There were marked differences in Cd concentrations between treatments. For example, uptake of Cd into herbage was greater where P fertiliser had been applied than not, and was greater from unlimed than limed soils. Offtake of Cd (mg ha(-1) year(-1)) was affected by large differences in yield and probably also by other factors. These include changes in botanical composition in the permanent grassland experiment; cultivar changes in the wheat and barley experiments; changes in soil organic matter and soil pH of some plots; changes in atmospheric deposition of Cd through time. All of these potentially confounding factors make the interpretation of results complicated. It is concluded, however, that, with one exception, there is little evidence of a long-term increase in crop Cd concentrations at Rothamsted.     

Impacts of logging and wildfire on an upland black spruce community in northwestern Ontario

Plant species composition and community structure were compared among four sites in an upland black spruce community in northwestern Ontario. One site had remained undisturbed since the 1930s and three had been disturbed by either logging, fire, or both logging and fire. Canonical correspondence ordination analyses indicated that herbaceous species composition and abundance differed among the disturbance types while differences in the shrub and tree strata were less pronounced. In the herb stratum Pleurozium schreberi, Ptilium crista-castrensis and Dicranum polysetum were in greatest abundance on the undisturbed forest site, while the wildfire and burned cutover sites were dominated by Epilobium angustifolium and Polytrichum juniperinum. The unburned harvested site was dominated by Epilobium angustifolium, Cornus canadensis and Pleurozium schreberi. Species richness was lower on the undisturbed site than on any of the disturbed sites while species diversity (H) and evenness (Hill's E5) were higher on the unburned harvested site than on the other sites. Results suggest that herb re-establishment is different among harvested and burned sites in upland black spruce communities and we hypothesize that differences in the characteristics of the disturbance were responsible, in particular, the impact of burning on nutrient availability. These differences need to be taken into account in determining the effects of these disturbances on biodiversity and long-term ecosystem management.     

Effects of environmental and maternally derived methylmercury on the embryonic and larval stages of walleye (Stizostedion vitreum)

The effects of environmental and maternally derived methylmercury (MeHg) on the embryonic and larval stages of walleye (Stizostedion vitreum) were investigated using eggs collected during two successive spawning seasons. Eggs were collected from fish in a mercury (Hg)-polluted environment (Clay Lake, Ontario, Canada), and from fish in two relatively pristine lakes (Lakes Manitoba and Winnipeg, in the province of Manitoba). Both bioaccumulation of Hg into muscle and its mobilization into eggs was significantly higher in Clay Lake females. Maternal muscle MeHg concentration was positively correlated with female length and egg MeHg was positively correlated with muscle MeHg concentration in all three populations. Hatching success of eggs from all three stocks declined significantly with increasing waterborne MeHg (0.1-7.8 ng l-1). Hatching success was not significantly affected by egg MeHg concentration. Embryonic heart rate declined with increasing waterborne MeHg concentration, but larval growth was not affected. Occurrence of larval deformities was negatively correlated with size of female, but was not significantly correlated with MeHg in either eggs or water. Larval MeHg was positively correlated with the concentrations of MeHg in eggs demonstrating transmission of MeHg from females. Uptake of ambient MeHg was higher in larvae exposed to higher waterborne MeHg concentrations.