Profiles of cuticular hydrocarbons mediate male mate choice and sexual isolation between hybridising <Emphasis Type="Italic">Chrysochus</Emphasis> (Coleoptera: Chrysomelidae)

Summary. Chemical signals frequently underlie sexual isolation between insect species. Our understanding of the evolutionary forces influencing these signaling systems is known for very few systems, challenging both our efforts to understand insect speciation, and our ability to predict long-term changes in the chemical communication systems of insects. Thus, we are in need of more systems in which both the chemical signals causing sexual isolation and the evolutionary forces driving sexual isolation are understood. Sexual isolation in the hybrid zone between Chrysochus cobaltinus and C. auratus has apparently increased in response to natural selection against hybridisation (i.e. reinforcement). Previous experiments suggested that this isolation was due, at least in part, to male preferences for conspecific females. Here, we confirm this role of male choice, and document that male mate choice in this system is influenced by cuticular hydrocarbon (CHC) profiles. Specifically, male C. cobaltinus responses to control cadavers and conspecific female cadavers painted with different cuticular hexane extracts, together with analyses of the composition of those extracts, revealed that male mate choice is governed by CHC profiles. Multivariate analyses of GC profiles demonstrated that those profiles are indeed both sex- and species-specific. Although GC-MS enabled identification and quantification of the specific cuticular hydrocarbons, we have not yet determined which individual compounds govern mate choice. Having established that CHCs influence sexual isolation in this system, we can now assess the evolutionary lability of these cues, which will inform both our understanding of speciation, and of the conditions under which the chemical signaling systems that influence mate choice in insects can evolve.     

Long-term increased bioaccumulation of mercury in largemouth bass follows reduction of waterborne selenium

Average mercury concentrations in largemouth bass from Rogers Quarry in east Tennessee were found to increase steadily following the elimination of selenium-rich discharges of fly ash to the quarry in 1989. From 1990 to 1998, mean mercury concentrations (adjusted to compensate for the covariance between individual fish weight and mercury concentration) in bass rose from 0.02 to 0.61 mg/kg. There was no indication that the rate increase was slowing or that mercury concentrations in fish were approaching a plateau or steady state. Mean selenium concentrations in bass declined from 3 to 1 mg/kg over the first five years of the study, but remained at 1-1.5 mg/kg (about twice typical concentrations in bass from local reference sites) for the last three years of the study. Gross physical abnormalities were common in fish from the site in the first three years after elimination of fly ash discharges but disappeared after two more years. Although it remains possible that other chemical or physical changes related to fly ash disposal in the system were associated with increased mercury bioaccumulation, the most likely explanation is that selenium played a critical role. It appears as though aqueous selenium enrichment was capable of having a profound effect on mercury bioaccumulation in this system but at the cost of causing a high incidence of gross abnormalities in fish. However, it is possible that selenium concentrations between the national ambient water quality criterion for the protection of aquatic life, 5 microg/l, and that now found in Rogers Quarry (<2 microg/l) could reduce mercury bioaccumulation without causing adverse effects on aquatic biota and fish-eating wildlife.     

Aerosol laser ablation mass spectrometry of suspended powders from PM sources and its implications to receptor modeling

Primary sources of particulate matter (PM) were analyzed by suspending powdered samples into an aerosol laser ablation mass spectrometer (LAMS). PM sources studied included vehicle exhaust particulates, dust from a non-ferrous smelter, cement powder, incinerator fly ash, two coal fly ash samples, and two soils. Marker peaks signified certain PM source sectors: construction particles could be distinguished by abundant Ca and Ca compounds, fuel combustion was marked by elemental carbon clusters, and nonferrous industrial particles showed inorganic As, Cu, Pb, Zn, and SOx. In addition to the distinction between particles from these different source sectors, mass spectral results also showed that for a single source, different particle types existed, and among different sources within a sector, similar spectra were present. The aerosol LAMS results show the difficulty in differentiating among separate fly ash sources as well as among different soil samples. A particle class balance receptor model that measures the amount of specific particle types rather than the amount of a chemical component is suggested as a means of source apportionment when particle spectra with overlapping source possibilities occur. The assumptions and limitations of receptor modeling aerosol LAMS data are also described. In particular, methods need to be developed to account for the contribution of secondary sources.     

Evidence of natural organochlorine formation in peat bogs

Peat samples from four ombrotrophic and two minerotrophic peat bogs in New Brunswick, Canada, have been analyzed for polychlorinated dioxins and furans (PCDD/DF's) as well as other organochlorine compounds. Data from each bog show occasional low levels of 2,3,7,8-substituted tetra-through octachloro dioxins and furans. Mono-through trichlorodioxins and furans have also been identified.

A consistent pattern was observed among the TCDD's and TCDF's which was reproducible across all peat samples analyzed. A single TCDF isomer (2468-TCDF) predominates over all other isomers whereas two isomers of TCDD were prominent (1,3,6,8-TCDD and 1,3,7,9-TCDD). This distinct isomer pattern is present at all depths and is different from that of atmospheric deposition or known sources of PCDD/DF's (eg. fly ash, pulp and paper effluent etc). The pattern is replicated with in vitro oxidative coupling of 2,4-dichlorophenol at pH 2.9 using a commercially available chloroperoxidase from the fungus Caldariomyces fumago.

Significant incorporation of ³⁶Cl-occurred in peat. Autoclaving decreased incorporation while adding casein hydrolysate increased it. The incorporation mirrored the metabolic activity (CO₂ production) of samples consistent with organochlorine synthesis being due to biological activity.

Total Organic Halide (TOX) levels in peat show a wide range in values reaching ca. 1000 ppm at mid-depth in the ombrotrophic Kelly's Bog. TOX in Kelly's Bog occurs at all depths and, since the topography probably excludes leaching from surrounding areas, a local origin of organochlorines is suggested.

Chloroform and a range of chlorinated aromatic compounds (chlorophenols, chlorophenoxy and chlorobenzoic acid derivatives) have also been identified in peat.

Our findings to date are consistent with hypothesis for a biogenic origin for at least some of the organochlorine compounds, including some of the PCDD/DF's, found in peat bogs.     

Towards sets of hazardous waste indicators. Essential tools for modern industrial management

Decision-makers require useful tools, such as indicators, to help them make environmentally sound decisions leading to effective management of hazardous wastes. Four hazardous waste indicators are being tested for such a purpose by several countries within the Sustainable Development Indicator Programme of the United Nations Commission for Sustainable Development. However, these indicators only address the 'down-stream' end-of-pipe industrial situation. More creative thinking is clearly needed to develop a wider range of indicators that not only reflects all aspects of industrial production that generates hazardous waste but considers socio-economic implications of the waste as well. Sets of useful and innovative indicators are proposed that could be applied to the emerging paradigm shift away from conventional end-of-pipe management actions and towards preventive strategies that are being increasingly adopted by industry often in association with local and national governments. A methodological and conceptual framework for the development of a core-set of hazardous waste indicators has been developed. Some of the indicator sets outlined quantify preventive waste management strategies (including indicators for cleaner production, hazardous waste reduction/minimization and life cycle analysis), whilst other sets address proactive strategies (including changes in production and consumption patterns, eco-efficiency, eco-intensity and resource productivity). Indicators for quantifying transport of hazardous wastes are also described. It was concluded that a number of the indicators proposed could now be usefully implemented as management tools using existing industrial and economic data. As cleaner production technologies and waste minimization approaches are more widely deployed, and industry integrates environmental concerns at all levels of decision-making, it is expected that the necessary data for construction of the remaining indicators will soon become available.     

Climate change mitigation strategies in the forest sector: biophysical impacts and economic implications in British Columbia,Canada

Managing forests to increase carbon sequestration or reduce carbon emissions and using wood products and bioenergy to store carbon and substitute for other emission-intensive products and fossil fuel energy have been considered effective ways to tackle climate change in many countries and regions. The objective of this study is to examine the climate change mitigation potential of the forest sector by developing and assessing potential mitigation strategies and portfolios with various goals in British Columbia (BC), Canada. From a systems perspective, mitigation potentials of five individual strategies and their combinations were examined with regionally differentiated implementations of changes. We also calculated cost curves for the strategies and explored socio-economic impacts using an input-output model. Our results showed a wide range of mitigation potentials and that both the magnitude and the timing of mitigation varied across strategies. The greatest mitigation potential was achieved by improving the harvest utilization, shifting the commodity mix to longer-lived wood products, and using harvest residues for bioenergy. The highest cumulative mitigation of 421 MtCO₂e for BC was estimated when employing the strategy portfolio that maximized domestic mitigation during 2017–2050, and this would contribute 35% of BC’s greenhouse gas emission reduction target by 2050 at less than $100/tCO₂e and provide additional socio-economic benefits. This case study demonstrated the application of an integrated systems approach that tracks carbon stock changes and emissions in forest ecosystems, harvested wood products (HWPs), and the avoidance of emissions through the use of HWPs and is therefore applicable to other countries and regions.     

A model of mining and exploring for exhaustible resources

A model of extractive industries is developed, in which firms select the time-paths of exploration and extraction that maximize their present values. Two externalities unique to the exploration process are found to distort industry behavior. Industry behavior is simulated under conditions of competition, monopoly, and central management, and the effects of percentage depletion allowances and changes in the discount rate are observed. Monopolists overconserve the resource and hold excess reserves; competitors who enter mineral lands freely tend to overexplore and overextract; percentage depletion allowances decrease reserves; and higher discount rates reduce extraction in the long run.     

Trace Element Contamination in Benthic Macroinvertebrates from a Small Stream Near a Uranium Mill Tailings Site

Direct measurement of the accumulation of non-radioactive traceelements in aquatic biota near uranium mining or processing sites has been relatively rare, with greater focus on the radiological activity in the adjacent soils and groundwater. To evaluate the potential ecological concern associated with trace elements at a former uranium mill site in southeasternUtah, benthic macroinvertebrates were collected and analyzed for 17 trace elements from multiple locations within a small on-site stream, Montezuma Creek, and a nearby reference stream. Key questions of this study relate to the spatial and temporalextent of contamination in aquatic biota, the potential ecological risks associated with that contamination, and the usefulness of benthic macroinvertebrates as a monitoring tool at this site. Composite samples of similar macroinvertebrate taxa and functional feeding groups were collected from each site over atwo year period that was representative of normal and dry-yearconditions. In both years, mean concentrations of arsenic,molybdenum, selenium, and vanadium were significantly higher (afactor of 2–4 times; P < 0.05) in macroinvertebrates collectedfrom one or both of the two Montezuma Creek sites immediatelydownstream of the mill tailing site in comparison toconcentrations from reference locations. Mean uraniumconcentrations in invertebrates immediately downstream of themill site were more than 10 times higher than at reference sites.The site-to-site pattern of contamination in Montezuma Creekinvertebrates was similar in 1995 and 1996, with mill-relatedtrace elements showing a downstream decreasing trend. However,nine of seventeen contaminant concentrations were higher in thesecond year of the study, possibly due to a higher influx of deepgroundwater during the drier second year of the study. Apreliminary assessment of ecological risks, based on the benthicmacroinvertebrate bioaccumulation data, suggests that aquatic andterrestrial population risks are low. Benthic macroinvertebratesappeared to be sensitive integrators of trace element inputs tothe aquatic environment from a former uranium mill tailing site,and provided useful spatial and temporal patterns ofcontamination not easily obtained using conventional surfacewater or groundwater measures.