No description available.

Methylmercury (MeHg) is the most toxic form of Hg to wildlife, partly because of its ability to biomagnify through the food chain. Previous studies have shown that river otter (Lutra canadensis) is particularly susceptible to increased exposure and body burdens of MeHg due to the piscivorous nature of its diet. The objectives of this study were to attempt to establish a relationship between MeHg concentrations in otter tissues and DNA fragmentation using single cell electrophoresis (comet assay) as well as evaluate the effectiveness of the comet assay as a tool in genotoxicity assessment in field samples. Results of preliminary experiments indicate that both time and storage temperature markedly influence the rate of spontaneous DNA degradation. Increased numbers of freeze/thaw cycling also appear to have a negative effect on DNA integrity. In addition, a cell culture experiment was set up to measure the effects of differing levels of MeHg on a neuroblastoma cell line.

No description available.

The Quebec City - Windsor corridor is the busiest and most important trade and transportation corridor in Canada. The transportation sector is the second largest greenhouse gas (GHG) emission category in the country. Governments around the world, including Canada, are considering increased mode share by rail as a way to reduce transportation emissions. To understand whether freight mode shift is a realistic means to reduce transportation emissions, an analytical model is needed that can predict the effect of government policy on mode split. / This thesis provides background on the freight transportation-GHG nexus in Canada and describes the development, implementation, reasoning behind, and results of, a Stated Preference shipper carrier choice survey for the Quebec City - Windsor corridor conducted during the fall of 2005. It then describes how the resulting carrier choice models are used to estimate the potential to displace truck traffic to rail (premium-intermodal) under current conditions, as well as to test the effectiveness of different possible future policy or service offering scenarios. / The results show that premium-intermodal has the potential to capture a substantial share of traffic between the main destinations in the Quebec City - Windsor Corridor. However, its ability to contribute significantly to reducing CO2 emissions is limited. According to the analyses conducted, potential reductions are considered to be in the range of nil to 0.413 Mt---a fraction of what the federal government was hoping to be able to achieve through "further public-private collaboration to promote the use of intermodal freight opportunities and to increase the use of low-emission vehicles and modes" (Government of Canada 2002). / At the same time, these potential reductions are based on a small proportion of total truck-related emissions and a few city-pairs. Extension of the current analysis to more city-pairs separated by longer distances might arrive at different conclusions.

The research was undertaken to simulate the surface transport of water and chemicals from a flat agricultural watershed at the Green Belt farm in Ottawa, Ontario, Canada. The GIS database created for the Black Rapid Creek watershed focused on attributes and data necessary to run a non-point source model for surface transport of water and chemicals called AGNPS. The GIS used in the current study was SPANS for the OS/2 warp (version 3) environment. The years of simulation for the study area were 1992 and 1993. The study was carried out on a watershed scale and flow routing from different cells to the outlet of the watershed was simulated with AGNPS under different management practices. The results of the study indicate that input variables of AGNPS model for a flat agricultural watershed, flow direction, precipitation event and topography of the land, affect the surface runoff volume at the outlet considerably. (Abstract shortened by UMI.)

Habitat selection by, ecological energetics of, and the effects of changes in white pine (Pinus strobus L.) forests on Red Crossbills (Loxia curvirostra) were studied in Algonquin Provincial Park, Ontario. Birds were surveyed in several forest habitats and daily activities were observed during the breeding season in the autumn of 1998, a good year for white pine seed production. During the autumn of 1997 and summer of 1998, surveys of white pine stumps from trees harvested in the mid-late 1800s were conducted. Breeding birds foraged in stands with a minimum of 40% white pine, and appeared to prefer stands, both mixed deciduous-coniferous (40--70% white pine) and pine (>70% white pine) along roads. Possible reasons for this were: (1) seeds from trees along the road were more available to birds; (2) open-grown trees along the road had larger crowns with more seeds; and (3) the road provided grit and was adjacent to a favorite foraging area. (Abstract shortened by UMI.)

No description available.

Metal-contamination of lakes simplifies food webs and reduces the efficiency of energy transfer to top trophic organisms, such as yellow perch (Perca flavescens). Benthic invertebrate community composition and yellow perch diet, growth and activity levels from lakes along a metal-contamination gradient were used to assess the importance of a naturally diverse prey base for maintaining energy transfer to growing fish, and how this is disrupted by metal-contamination. As perch grow larger, they shift their diet to larger prey; otherwise, the activity costs of foraging for many, small prey, instead of a few large prey, become too high and the fish stop growing. Metal contaminated lakes have less diverse zoobenthic communities, particularly the lack of large bodied invertebrate taxa, forcing perch to rely on smaller benthic prey. Perch from metal-contaminated lakes display slow growth and poor condition during benthivory. Estimates of fish activity, using the activity of the glycolytic enzyme Lactate dehydrogenase in perch white muscle tissue as a proxy, suggest that diet shifts to larger prey lower activity costs and may explain how diet shifts maintain growth efficiency as perch grow larger. Perch from metal-contaminated lakes cannot benefit from the energetic advantages of switching to larger prey and thus exhibit poor growth.

This study is an analytical examination of a stylistic anomaly observed among Middleport Iroquoian village sites (dating c. A.D. 1300-1450) located near Crawford Lake in southcentral Ontario, Canada. The anomaly is characterized by differing percentages of two forms of ceramic smoking pipes from closely spaced, contemporaneous village sites. This distinction occurs throughout southern Ontario, but is particularly pronounced in the Crawford Lake area. In order to develop and test a model to explain this anomaly, an approach employing a hierarchy of inference, including formal, spatial, temporal, economic, social, and cultural levels, is proposed. This is applied to an analysis of pottery and smoking pipes from eight Middleport sites. The key elements of the explanation are: (1) the two styles represent two distinct prehistoric communities; (2) these communities competed with each other for limited resources; and (3) they symbolized this competition through differences in pipe styles. This conclusion indicates that both the material culture and social relations among Middleport communities may be more complex than has previously been inferred.

No description available.