Phosphorus release from sediments contributes significantly to high phosphorus level in lake water and provides nutrient support to promote algal growth. To speed up the recovery of eutrophic lakes, it is necessary to limit phosphorus release from sediments. Accurate sedimentary phosphorus fractionation is a strong basis for understanding phosphorus release from sediments. There are several techniques to study sedimentary phosphorus fractionation. Chemical sequential extraction (CSE) techniques are commonly used by industrial practitioners. However, it is doubtful that the P fractionation of the lake sediments studied using the Jensen and Thamdrup (1993) method is reliable. The reason is that the phosphorus fractions do not exactly correspond to the chemically defined compounds in the sequential phosphorus extraction. In order to further understand the Jensen and Thamdrup (1993) method, it is necessary to study P species in the supernatant and residue of each fraction. X-ray absorption near-edge structure (XANES) can provide direct information about the mineral phase of phosphorus in the sediments. Solution phosphorus nuclear magnetic resonance (31P NMR) reveals direct molecular and structural characterization of organic phosphorus in the sediments. This study enhanced the understanding of the Jensen and Thamdrup (1993) chemical sequential extraction method for studying the sedimentary phosphorus fractionation by using solution 31P NMR spectroscopy and phosphorus K-edge XANES spectroscopy. The research using the chemical sequential extraction indicated that inorganic P was dominant in all sediments samples. Also, it suggested that calcium-bound P accounted for the largest proportion of the total P in every sediments sample. The solution 31P NMR spectroscopy clearly identified orthophosphate, phytic acid, pyrophosphate, and polyphosphate in the sediments samples. The P K-edge XANES spectroscopy showed all of the sediments samples contained apatite and phytic acid. In addition, the study using the XANES identified apatite in the residue after the HCl extraction of Blackstrap #6; however it indicated no apatite in the supernatant of HCl fraction of both Blackstrap #3 and Pond #11.

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Sediments in Lake C3, Ellesmere Island, Canada, contain annual laminations, providing a record of sediment accumulation for 1900+ years. Marine sediments are also present at base of cores, recording lake isolation following isostatic rebound of the Taconite Inlet region in the mid-Holocene. Beyond weak correlations with snowfall and summer temperature and precipitation, varve thickness comparisons with instrumental data were largely unsuccessful, likely due to turbidite-induced erosion. However, summer climate conditions are of key importance in varve thicknesses at many Arctic sites and we expect this to be true at Lake C3. Trends in the thickness record also correspond in approximate timing and response to large-scale climate events including the Little Ice Age (thin laminations) and the Medieval Warm Period (thick laminations). Long term trends and variability in the thickness record are also likely influenced by the weakening flow of the Taconite River following deglaciation as well as localized geomorphic events. Elemental profiles combined with varve thickness features identify anoxic periods resulting from ice-cover- or marine incursion- induced stratification. Through synthetic aperature radar imagery we verify the strong link between air temperature and ice-cover conditions during the summer. Modification to tephra isolation methods resulted in the successful extraction of cryptotephra. Shards are currently undergoing microprobe identification to identify volcanic source and eruption timing. Sediments at Lake C3 provide a high-resolution record of local and regional environmental change and add to the high-latitude network of reconstructions with the objective of placing current changes in a long-term context.

Pacific salmon has been a staple resource for residents of British Columbia for over seven thousand years. Archaeological evidence obtained from a shell midden at Namu, B.C., provides detailed information about the diets of the First Peoples living at Namu over the past seven thousand years. Pacific salmon was the most prevalent species of fish uncovered within the midden, excluding herring. Pink, chum and sockeye species were consumed in the greatest quantities. Pink was particularly favored because of its ability to store over winter months without spoiling. Evidence from the shell midden also reveals fluctuations within the pink salmon fishery from ~3800 until 1900 cal year BP. The paleoenvironmental conditions within Namu Lake during the time of the pink collapse have never before been explored. There is also little evidence pertaining to what may have contributed to the collapse of the pink fishery. Sediment cores collected from Namu Lake, B.C. provide evidence for paleoenvironmental conditions that may have contributed to fluctuations in the pink salmon population. Particle size analyses of lake sediment cores indicate changes in river discharge as well as erosional intensity within the Namu basin. Particle size, coupled with radiocarbon dating, reveal a transitional period within the basin from ~ 3200 to 2200 cal year BP. A decrease in elemental ratios/Al, particularly Ca, Na, Ba, and Sr, provides evidence for a decline in erosional intensity and a relatively drier period within the basin. The decrease in erosional intensity could be due to consistently drier conditions at Namu. A resulting reduction in the flow of the Namu River would have caused an increase in finer particles within the pink salmon spawning grounds. Average C/N ratios for NC1 are 26.28, indicating that organic matter within the lake is mainly terrestrial in origin. These results, combined with the particle size and trace metal analysis, reveal that river discharge and slope wash had declined during this period causing fine material to remain in the Namu River (outflowing), which is the spawning grounds for the pink salmon, rather than being transported out into the bay. The results of this study reveal that a shift in moisture, towards relatively dry conditions, negatively impacted spawning pink salmon at Namu Lake. This study provides insight into the sensitivity of Pacific salmon to climate and the effects future climate change may have on the species. The ability of environmental data to supplement and enhance archaeological information and interpretations of prehistoric conditions is illustrated throughout this study. The cores collected at Namu Lake also reveal the need for site specific climatic data in order to accurately interpret archaeological contexts and conditions. / Thesis / Master of Science (MSc)

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Questions remain regarding the impacts of late-Holocene human activities and environmental change on landscapes of the Caribbean islands. This dissertation examined the long-term environmental history of two sites in the northern Caribbean primarily through the analysis of proxy data sources contained in sediment cores. At Laguna Alejandro, a coastal lagoon in the southwestern Dominican Republic, we interpreted, from sediment lithology and stable oxygen isotope data, at least ten storm events over the past 1,000 years, producing the first long record of storm activity from the island. During the Little Ice Age (1400−1800 CE), we interpreted an increased frequency of hurricane landfalls at the study site with longer ecosystem recovery times and decreased fire activity versus during earlier, more moist periods of the late-Holocene. At Freshwater Pond, an inland pond on Barbuda, we interpreted vegetation disturbance from presence of disturbance pollen taxa and biomass burning near the pond from abundance of macroscopic (>125 µm) charcoal from sediments representing ~150 BCE–1250 CE, with consistency of burning and human history on the island informed by the archaeological record suggesting fire activity was primarily due to Pre-Columbian inhabitants. Microscopic charcoal analysis indicated that extra-local burning, primarily island-wide, continued until ~1610 CE then declined, possibly reflecting a change in land-use practices by Europeans who entered the region in 1492 CE and established a permanent settlement on the island in the 1660s. My study on modern pollen from surface soils and sediments, the first from lowland seasonally-dry vegetation of the Greater Antilles, informed our ideas on vegetation-pollen representation in different plant communities, including tropical dry forest, thorn forest, mangrove, mudflat, and lagoon. My modern pollen results also aided in the interpretation of stratigraphic pollen in the study of nearby L. Alejandro’s sediments and revealed changes in floristic composition at the study site through time. Pollen of maize (Zea mays) and Prosopis juliflora in sediments representing ~1760 CE document human subsistence agriculture and disturbance to tropical dry forest in the watershed. / PHD

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The $ sp3$H thymidine incorporation (TTI) method has been frequently used to estimate benthic bacterial production rates in well oxygenated marine and river sediments, but not in the frequently more reduced lake sediments. In chapter 1, I evaluate the published sediment production literature and examine useful predictors of in situ bacterial production in mostly marine and riverine sediments. In chapters 2 and 3, I estimated and compared benthic production rates by TTI, frequency of dividing cells (FDC), the dilution method (DIL) and sediment respiration (SR) in 13 Quebec lakes to assess the reliability of the TTI based production rates. The TTI method was first calibrated, but despite keeping incubation times short and at in situ temperature, using optimal sediment volumes to saturate $ sp3$H thymidine (TdR) uptake rates, and correcting production rates for $ sp3$H-DNA recovery efficiencies, only a maximum of 10% of $ sp3$H TdR was incorporated into DNA and only extracellular isotope dilution could be accounted for (chapter 2). Most problematic, however, is the increasing presence of active bacteria unable to take up and incorporate TdR as lake sediments become more reduced (chapter 3). TTI based results are also not nearly as well correlated to environmental factors as those obtained from SR. (Abstract shortened by UMI.)

Environmental regulation of nitrogen cycling processes, denitrification and nitrification, was studied in sediment of Hamilton Harbour, with particular emphasis on the role of CH$ sb4$ metabolism (production and consumption). Through extensive sediment sampling and numerical analysis, it was found that particulate carbon was the best predictor of potential for anaerobic production of CH$ sb4$ and CO$ sb2$. The only predictor of denitrification capacity was anaerobic CO$ sb2$ production, indicating that beside NO$ sb3 sp-$ and O$ sb2$, a biotic factor involved in carbon metabolism may be important in the control of this activity. / Suppression of aerobic N$ sb2$O production in sediment slurries by C$ rm sb2H sb2$ and correlation with NO$ sb3$-production indicated that it was dependent on chemolithotrophic nitrification. Although CH$ sb4$ (1 to 24 $ mu$M) stimulated production of NO$ sb3 sp-$ and N$ sb2$O, we found that CH$ sb4$ at 84 $ mu$M or greater suppressed nitrification. Following extensive studies of pore water chemistry, potential microbial activities, and counts of nitrifiers and methanotrophs, we found that CH$ sb4$ oxidation (i) is more likely to suppress nitrification by competition for O$ sb2$ and NH$ sb4 sp+$ between methanotrophs and nitrifiers, and (ii) may be more important than nitrification as a sink of hypolimnetic O$ sb2$ in Hamilton Harbour. / Amongst a number of inhibitors, allylsulfide was found to be a differential inhibitor with much less effect on CH$ sb4$ oxidation in sediment slurries or in axenic cultures of Methylosinus trichosporium OB3b than on nitrification in sediment slurries.