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The use of critical loads of acidity to quantify damage to sensitive components of terrestrial and aquatic ecosystems has developed rapidly over the last decade. While much work has focused on defining damage to forested ecosystems, surface waters and groundwaters, there has been little work done on defining critical loads of acidity for ombrotrophic and minerotrophic peat. This thesis presents a modelling approach to quantify damage to ombrotrophic peat ecosystems, since such damage can result in a decline in both surface water quality and the ability of peat to act as an absorbent to aerial pollutants. Initial investigations were concerned with the factors which could be included in investigations of critical loads of N and acidity to the surface organic horizons of forest and moorland soils. The modelling approach was then developed from a series of laboratory-based simulation experiments to investigate the effect of contents of H&'43 , Ca2&'43 and Mg2&'43 in rainfall upon the chemistry of the peat ion exchange complex. The basic tenet of the modelling approach was that ion exchange equilibria for peat is rapid, mineral input to the surface of ombrotrophic peat from mineral weathering is negligible and that atmospheric inputs of wet and dry deposition will dominate the peat chemistry. These simulation experiments provided peat pH values resulting from equilibration with the simulated rainfall. By combining these with databases of atmospheric depositon for the U.K., critical loads of acidity and the present day peat pH were calculated and mapped. The critical load values for peat thus obtained were incorporated in the U.K. Critical Load mapping program, which was used to support the on-going European negotiations of emission reduction within the United Nations Convention on Long-range Transboundary Air Pollution (U.N. E.C.E. C.L.T.A.P.).

The relationships between C:N:P (carbon, nitrogen, and phosphorus) stoichiometry of Cladophora glomerata and land use characteristics in selected nearshore areas of the lower Laurentian Great Lakes were determined during two years of field sampling of coastal areas. In the past, bi-national reduction of point sources of P-loading resulted in reduced C. glomerata biomass; however, currently C. glomerata is resurging and it has been suggested that non-point source P loading, which may have increased with increasing populations and coastal land use changes, may be the cause. Study of the Halton shoreline, Lake Ontario, in 2006 demonstrated that C. glomerata nutrient stoichiometry has a strong seasonal relationship as internal P concentrations at 2 and 5 m depths decline to as low as 0.5 μg/mg dw during the rapid early summer growth period, well below the literature value of 1.6 μg/mg dw indicative of P limitation. Samples at 10 m maintained a constant surplus in P throughout the summer as light was the greater controlling factor at this depth. Along with ambient dissolved P, C. glomerata internal P increased sharply during the September and October surveys to approximately 3.5 μg P/mg dw at 2 m stations. Throughout the 2006 growing season both water chemistry and C. glomerata nutrient stoichiometry did not identify any direct point source influencing algal growth as indicated by tissue stoichiometry. Land use comparisons between the urbanized Halton region and the non urban sites of Presqu’ile Provincial Park and Peacock Point (Lakes Ontario and Erie, respectively) indicated significantly higher enrichment in both nitrogen and phosphorus at the 10 m urban stations as internal P concentrations were elevated and both N and P nutritional status indicators (C/P, C/N, and N/P) were much lower compared with non-urban sites. Areas with relatively more human impact (Port Credit and Halton on Lake Ontario) had higher internal P concentrations in C. glomerata. Through empirical evidence, nutrient status ratios predict the onset of P limitation for Cladophora glomerata within the Great Lakes to have values for C:P > 505 and N:P > 41, whereas zero positive growth was estimated to begin when C:P > 1246 and N:P > 75. Natural stable isotope abundances of 13C were indicative of benthic algal production as δ13C values from C. glomerata tissue samples during the early summer rapid growth period varied with depth to the 5 m depth contour. Though, overall 13C algal signals were a function of offshore changes in DIC-δ13C patterns throughout the year they were consistently lower in Cladophora tissue at shallower depths suggesting high photosynthetic demand for CO2 reduced isotopic photosynthetic fractionation. This trend was evident along most shorelines and from year to year, verifying the use of 13C stable isotope to define periods of potentially carbon-limited production. 13C and 15N did not identify any significant difference between urban and non urban shorelines. Similarly, stable isotopes were inconclusive in measuring local point source impacts. Similarly, point sources were also not apparent from measuring water chemistry and C. glomerata tissue parameters. The use of 15N isotopes in tracing C. glomerata filament origins may be of merit as persistent depth relationships were observed at all sites in Lake Erie and Ontario.

The relationships between C:N:P (carbon, nitrogen, and phosphorus) stoichiometry of Cladophora glomerata and land use characteristics in selected nearshore areas of the lower Laurentian Great Lakes were determined during two years of field sampling of coastal areas. In the past, bi-national reduction of point sources of P-loading resulted in reduced C. glomerata biomass; however, currently C. glomerata is resurging and it has been suggested that non-point source P loading, which may have increased with increasing populations and coastal land use changes, may be the cause. Study of the Halton shoreline, Lake Ontario, in 2006 demonstrated that C. glomerata nutrient stoichiometry has a strong seasonal relationship as internal P concentrations at 2 and 5 m depths decline to as low as 0.5 μg/mg dw during the rapid early summer growth period, well below the literature value of 1.6 μg/mg dw indicative of P limitation. Samples at 10 m maintained a constant surplus in P throughout the summer as light was the greater controlling factor at this depth. Along with ambient dissolved P, C. glomerata internal P increased sharply during the September and October surveys to approximately 3.5 μg P/mg dw at 2 m stations. Throughout the 2006 growing season both water chemistry and C. glomerata nutrient stoichiometry did not identify any direct point source influencing algal growth as indicated by tissue stoichiometry. Land use comparisons between the urbanized Halton region and the non urban sites of Presqu’ile Provincial Park and Peacock Point (Lakes Ontario and Erie, respectively) indicated significantly higher enrichment in both nitrogen and phosphorus at the 10 m urban stations as internal P concentrations were elevated and both N and P nutritional status indicators (C/P, C/N, and N/P) were much lower compared with non-urban sites. Areas with relatively more human impact (Port Credit and Halton on Lake Ontario) had higher internal P concentrations in C. glomerata. Through empirical evidence, nutrient status ratios predict the onset of P limitation for Cladophora glomerata within the Great Lakes to have values for C:P > 505 and N:P > 41, whereas zero positive growth was estimated to begin when C:P > 1246 and N:P > 75. Natural stable isotope abundances of 13C were indicative of benthic algal production as δ13C values from C. glomerata tissue samples during the early summer rapid growth period varied with depth to the 5 m depth contour. Though, overall 13C algal signals were a function of offshore changes in DIC-δ13C patterns throughout the year they were consistently lower in Cladophora tissue at shallower depths suggesting high photosynthetic demand for CO2 reduced isotopic photosynthetic fractionation. This trend was evident along most shorelines and from year to year, verifying the use of 13C stable isotope to define periods of potentially carbon-limited production. 13C and 15N did not identify any significant difference between urban and non urban shorelines. Similarly, stable isotopes were inconclusive in measuring local point source impacts. Similarly, point sources were also not apparent from measuring water chemistry and C. glomerata tissue parameters. The use of 15N isotopes in tracing C. glomerata filament origins may be of merit as persistent depth relationships were observed at all sites in Lake Erie and Ontario.

Thesis (M. Sc.)--York University, 2002. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 186-198). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ71626.

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The effects of pollutant burdens on natural cyclic patterns in aquatic ecosystems have been studied, to test the hypothesis that a parameter or parameters describing the <I>pattern of variation </I>in a single determinant, such as DO or pH, may be used to describe the status of a body of water more meaningfully than results from single spot measurements. In this study the background water quality in a Scottish and a Ghanaian lake was assessed, then <I>rafts </I>were built on the lakes (Myrtle Dam and Weija Lake respectively) creating three small lakes to test the effects of pollutant loads (<I>e.g. </I>organics and nutrients) on them. Laboratory investigations to study the behaviour of the pollutants on DO or pH cycles were carried out, and then a dynamic DO model was developed to describe the cyclic behaviour of DO. Finally, the model was used to investigate the effects of added pollutant burdens on the DO cycles. Water quality assessment of Myrtle Dam and Weija Lake by using the <I>Weighted Water Quality Index </I>proved that Weija Lake has doubtful quality with WQI 51, which needs improvement. Myrtle Dam WQI of 73 shows that the lake waters are unpolluted (or recovered from pollution). It is also well oxygenated at the surface and receives no toxic discharge. The <I>raft</I> experiments for Myrtle Dam and the Weija Lake have been used to demonstrate that, in the raft tubes, organic loadings do have effects on the oxygen cycles, and showed that there are two effects. One is that, with a small organic loading, the mean DO value dropped, then increased as the organic loading was consumed. The second is that the amplitude of the DO cycle increased as the organic loading increased from 2.5 to 5.0 mg L^-1 TOC for Myrtle Dam, and decreased for Weija Lake as the organic loading increased from 2.5 to 5.0 mg L^-1 TOC. The laboratory experiments in both Ghana and Aberdeen proved to be useful in explaining the effects of nutrients and trace elements on the DO cycles. It was evident that the higher the algal concentration, the greater was the DO cycle and 30% v/v (<I>c.a. </I>254 mg L^-1 chlorophyll 'a' content ≍ 17 g L^-1 biomass aqueous algal suspension) proved to be the most suitable concentration for investigations, because, with higher organic loadings, the 100% aqueous algal suspension proved to be too concentrated and caused total deoxygenation.

The circumpolar Arctic is experiencing dramatic environmental changes that are already impacting tundra ecosystems and northern communities that are intimately linked to the land. Increasing permafrost degradation, shrub encroachment, larger and more frequent fires, and increasing human development have significant effects on biotic and abiotic conditions in the lower Peel River watershed, NT. To understand and respond to rapid environmental changes, diverse knowledge perspectives are needed, so my M.Sc. research uses scientific and social scientific approaches to investigate environmental change in the lower Peel River watershed. I investigated the impacts of the Dempster highway on plants, soils and permafrost in the Peel Plateau by conducting field surveys at sites dominated either by tall alder (Alnus crispa) shrubs or by dwarf shrubs, at 30 m and 500 m from the highway. At each site I measured vegetation composition, alder growth, soil nutrients, litter and organic layer thickness, active layer thickness, and snow depth. We found that alder growth and recruitment were enhanced adjacent to the Dempster Highway, and dramatic alterations to plant community composition, soil properties and ground temperatures were observed where alder shrubs had formed closed canopies. Tall shrub sites adjacent to the road exhibited lower abundance of understory vegetation including mosses, greater litter and organic soil thickness, higher nutrient availability, and deeper snowpack. Biotic and abiotic changes associated with road effects feedback with alder canopy development, and have important implications for permafrost conditions adjacent to the roadbed, and potentially on road bed performance. This research contributes to our understanding of environmental changes caused by the highway and their consequences for infrastructure stability and pan-Arctic changes in vegetation cover. In a separate but complementary effort, I worked with Teetl’it Gwich’in land users and youth from Fort McPherson, NT to map observations of environmental conditions and changes. In the pilot year of a community-based environmental monitoring program, we employed participatory multimedia mapping with Teetl’it Gwich’in land users and youth from Fort McPherson, NT. I accompanied Gwich’in monitors on trips on the land to document environmental conditions and changes. Observations made by land users were documented using photos, videos and audio taken by youth, and land users provided detailed information about each observation in follow-up interviews. I compiled observations (photo/video, GPS location, and interview audio and transcript) into a web-based map where the public will be able to see changes on the land in the images and words of Gwich’in land users. The online map will provide a medium for local residents to communicate their knowledge and concerns about the environment, and will be useful for land management and planning, environmental monitoring, and adaptation. / Graduate / 0768 / 0329 / 0326 / hkgill@uvic.ca

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Made available in DSpace on 2014-10-09T12:33:07Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:17Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP