Petroleum hydrocarbons are emitted into the environment via natural and anthropogenic activities. Once emitted, these hydrocarbons can be transported globally, persisting and accumulating in aquatic ecosystems. In the Alberta oil sands region (AOSR), mining activities have significantly altered and polluted the surrounding aquatic and terrestrial environments with heavy metals and various petroleum hydrocarbons including polycyclic aromatic hydrocarbons (PACs). Though PACs have been tracked through time using dated lake sediment cores, separating natural and anthropogenic PACs can be difficult. In the Peace Athabasca Delta (PAD) this task is especially difficult as this region has been receiving annual inputs of naturally eroded bitumen throughout history. Petroleum biomarkers are unique petrogenic compounds (i.e. derived from petroleum) which may provide a secondary proxy to track mining impacts. This thesis investigated the impacts of mining activities on the AOSR and the PAD using two different proxies, PAC and petroleum biomarkers. These two regions were compared to reference lakes to the south and northwest of the Athabasca oil sands formation, in order to provide a natural signal, with minimal oil sands mining contamination. Historically deposited PACs and petroleum biomarkers were analysed in radiometrically dated lake sediment cores from the AOSR and the PAD, Alberta. Sediment profiles in the AOSR (Saline Lake) showed increases in PAC fluxes for both alkylated and parent compounds coeval with mining activities. Alkylated PAC fluxes in reference lakes (Mariana Lake and BM11) increased at the height of oil sands development (1990s). PAD lakes showed no statistical increase in PAC flux through time due to high levels of naturally eroded bitumen entering the system. Parent PAC diagnostic ratios, however, showed clear shifts from pyrogenic (primarily wood burning) in pre-development sediments to petrogenically derived PACs in modern sediments, in both AOSR and PAD lakes, coeval with oil sands development. Petroleum biomarker diagnostic ratios in Saline Lake and PAD lakes remained stable through time, indicating a clear current and historical petroleum signal originating from the AOSR. Reference lakes (Mariana Lake and BM11) showed the greatest change in petroleum biomarkers. Historically, these lakes had signatures uncommon of petroleum sources, however, in recent years petroleum inputs from mining development were revealed by these petroleum biomarkers. This study compared the historical trends of several petroleum hydrocarbons in lake sediment to the historical emissions of these petroleum hydrocarbons from oil sands mining operations. Notably, we show the potential for petroleum biomarkers to trace petroleum hydrocarbon contamination in the environment.

This thesis combines detailed analyses of living plant communities with paleolimnological methods to develop the use of plant macrofossils as an effective tool to track hydroecological changes in ponds of the Slave River Delta (SRD), N.W.T. Several approaches were used to develop an understanding of the relationships between hydrolimnological conditions, living plant communities, and the composition of sedimentary macrofossil remains across spatial and temporal scales. A spatial survey approach was used to assess the relationships between the composition of plant macrofossil assemblages contained in the surface sediments and the hydrological and limnological conditions of 40 SRD basins that span a broad range of hydrological settings in the delta. Results show that there are strong relationships between the prevailing hydrolimnological conditions in the SRD and the composition of sedimentary macrofossil remains, and subsequently indicator macrofossil taxa were identified to distinguish between sites with high river influence (flood-dominated sites: ostracode shells, Daphnia ephippia, Chara oospores; exchange-dominated sites: Myriophyllum winter-bud scales, Daphnia ephippia) and sites with low river influence (evaporation-dominated: Ceratophyllum leaves, Lemna leaves, Drepanocladus leaves). In light of the strong connection between spring flood events and the hydrolimnological conditions of SRD ponds, and growing concerns that the frequency of spring floods have declined in recent decades, paleolimnological investigations were initiated at a pond (SD2) adjacent to the Slave River to construct a record of flood events in the SRD. Prior to analysis of macrofossil assemblages from sediment cores, a detailed study of the living plant community was conducted at SD2, and results were compared to the distributions of surficial sedimentary plant macrofossil assemblages to assess how representative surficial sediment assemblages are of the living plant community. This study indicates distinct patch-scale (or quadrat-scale)similarity between the living vegetation and sedimentary remains in the central basin, as well as distinct similarity between the living aquatic macrophytes and sedimentary remains at a pond-scale, suggesting there is excellent potential to track changes in the composition and percent cover of aquatic macrophytes in pond sediment cores using plant macrofossil assemblages. Additionally, this study indicates that influence of long-distance transport of macrofossils during the 2005 flood event was minor at this pond, and may not be an important factor affecting paleolimnological reconstructions of plant communities. With contemporary studies as a framework, an ~90-year record of ice-jam flood frequency was reconstructed from a sediment core collected from pond SD2. Multi-proxy analyses indicated decadal-scale oscillations in flood frequency at this site, with at least three multi-year periods of low river influence. Beginning in ~1943, an 18-year period of particularly low river influence and greatly reduced water levels was indicated by abundant macrofossils of Sagittaria cuneata and represents the driest period over the past ~90-years. Similarities between the flood history of SD2 and upstream sites in the Peace-Athabasca Delta suggest that spring discharge generated from headwaters and major contributing rivers plays a key role in the frequency and magnitude of spring flood events of both deltas.

This thesis combines detailed analyses of living plant communities with paleolimnological methods to develop the use of plant macrofossils as an effective tool to track hydroecological changes in ponds of the Slave River Delta (SRD), N.W.T. Several approaches were used to develop an understanding of the relationships between hydrolimnological conditions, living plant communities, and the composition of sedimentary macrofossil remains across spatial and temporal scales. A spatial survey approach was used to assess the relationships between the composition of plant macrofossil assemblages contained in the surface sediments and the hydrological and limnological conditions of 40 SRD basins that span a broad range of hydrological settings in the delta. Results show that there are strong relationships between the prevailing hydrolimnological conditions in the SRD and the composition of sedimentary macrofossil remains, and subsequently indicator macrofossil taxa were identified to distinguish between sites with high river influence (flood-dominated sites: ostracode shells, Daphnia ephippia, Chara oospores; exchange-dominated sites: Myriophyllum winter-bud scales, Daphnia ephippia) and sites with low river influence (evaporation-dominated: Ceratophyllum leaves, Lemna leaves, Drepanocladus leaves). In light of the strong connection between spring flood events and the hydrolimnological conditions of SRD ponds, and growing concerns that the frequency of spring floods have declined in recent decades, paleolimnological investigations were initiated at a pond (SD2) adjacent to the Slave River to construct a record of flood events in the SRD. Prior to analysis of macrofossil assemblages from sediment cores, a detailed study of the living plant community was conducted at SD2, and results were compared to the distributions of surficial sedimentary plant macrofossil assemblages to assess how representative surficial sediment assemblages are of the living plant community. This study indicates distinct patch-scale (or quadrat-scale)similarity between the living vegetation and sedimentary remains in the central basin, as well as distinct similarity between the living aquatic macrophytes and sedimentary remains at a pond-scale, suggesting there is excellent potential to track changes in the composition and percent cover of aquatic macrophytes in pond sediment cores using plant macrofossil assemblages. Additionally, this study indicates that influence of long-distance transport of macrofossils during the 2005 flood event was minor at this pond, and may not be an important factor affecting paleolimnological reconstructions of plant communities. With contemporary studies as a framework, an ~90-year record of ice-jam flood frequency was reconstructed from a sediment core collected from pond SD2. Multi-proxy analyses indicated decadal-scale oscillations in flood frequency at this site, with at least three multi-year periods of low river influence. Beginning in ~1943, an 18-year period of particularly low river influence and greatly reduced water levels was indicated by abundant macrofossils of Sagittaria cuneata and represents the driest period over the past ~90-years. Similarities between the flood history of SD2 and upstream sites in the Peace-Athabasca Delta suggest that spring discharge generated from headwaters and major contributing rivers plays a key role in the frequency and magnitude of spring flood events of both deltas.

abstract / Earth Sciences / Master / Master of Philosophy

Wildfire is an ecological disturbance that plays an important role in ecosystem function and interacts with climate and vegetation, relationships that may be altered by ongoing climate change. Insights from paleoecology can provide context for environmental change, including the natural range of variability. Here, the Holocene fire history of a small watershed in eastern Ontario, Canada is reconstructed. A high-resolution macroscopic charcoal series was derived from the lacustrine sediment of Mud Lake, north of Gananoque, Ontario and within the Frontenac Arch. Analysis of the charcoal record estimates a mean fire-return-interval (FRI) of 175 yr/fire around Mud Lake during the Holocene, and similar mean FRIs during different time periods indicates that it has been a largely stationary fire regime. The analysis suggests that fire activity may have recently increased, but a lack of documentary fire records for the area leaves this uncertain. There is no indication that humans have significantly impacted the fire regime, though anthropogenic ignition could have played a role in the area’s recent fires. The fire regime around Mud Lake does not appear to have shifted in association with major changes in regional vegetation. Fire activity does correlate with some paleoclimate trends. The estimated fire frequency decreased around 7500 yr BP, when wetter summers became more common in eastern Canada, and a recent increase in fire frequency would parallel with more frequent incursions of dry and cool air masses into the region. During other parts of the record, however, the fire activity does not appear to reflect the major climate impacts. The fire history of Mud Lake is relevant to the ecological management of eastern Ontario’s St. Lawrence Islands National Park and its restoration of a rare, fire-dependent tree species, the pitch pine. Though predictions vary, this area’s climate may become more favorable to fire through an increase in temperature and a decrease in summer precipitation. By providing information about the natural variability of fire activity in eastern Ontario, this research can be applied towards setting appropriate management goals during future environmental change. / Thesis (Master, Environmental Studies) -- Queen's University, 2010-02-01 00:14:00.711

The boreal forest region of Canada is climatically sensitive and may be impacted by anthropogenic-induced climatic changes. The results of this multi-proxy paleolimnological study contribute detailed information on changes to the boreal forest in northwestern (NW) Ontario, showing unequivocal changes in lake and forest structure due to climate during the warmer mid-Holocene. This study uses diatoms, pollen, and charcoal reconstructions to better understand the timing and extent of climate-related changes in Lake 239, Experimental Lakes Area (ELA), in NW Ontario throughout the Holocene with an emphasis on the warmer mid-Holocene. Diatom analysis revealed changes in water quality based on analysis of species assemblages and quantitative inferences of total phosphorus from a deep central core. Lake levels at least 8-m lower than today were inferred from a near-shore core and were concurrent with an increase in nutrient-rich diatom assemblages, an increase in diatom accumulation, and a decrease in chrysophytes relative to diatoms in the central core. A concurrent increase in pollen such as Cupressaceae and Ambrosia indicate more open boreal forest between ~4500-8000 cal yr BP. Pollen-based inferences of temperature suggest an increase on average of 1-2°C warmer than today with winter temperatures up to 4°C warmer. The pollen inferences also suggest enhanced precipitation, but with increased evaporation/evapotranspiration resulting in reduced moisture availability overall. A transect of cores surrounding ELA was synthesized using pollen-based reconstructions of temperature and precipitation to assess regional changes. All sites show shifts in pollen assemblages indicating a warmer mid-Holocene; prairie sites to the west show mid-Holocene decreases in precipitation relative to today, whereas sites near or east of ELA show consistent increases in precipitation, but with enhanced evaporation. Charcoal analysis shows an increase in charcoal accumulation during the mid-Holocene warm period compared to the early and late Holocene, suggesting a more active fire regime. Fire return intervals based on type-M charcoal show a pronounced decrease during the early-to-mid Holocene period and a corresponding increase in fire frequency, whereas fire frequency derived from total charcoal was virtually unchanged over the Holocene. This study helps fill a knowledge gap in NW Ontario noted by several large regional assessments. / Thesis (Ph.D, Biology) -- Queen's University, 2010-07-15 09:54:18.653

Freshwater systems in Canada are affected by a multitude of environmental stressors, including cultural eutrophication, introduction of non‐native species, and climate change. Multiple stressors can interact in unpredictable ways and generate novel ecological scenarios, thus creating challenges for lake management. Lake Simcoe is an example of an aquatic system impacted by multiple stressors, facing management challenges of deteriorating water quality and coldwater fisheries. In order to better understand stressor interactions and pre‐disturbance lake conditions, a long‐term perspective is necessary. Therefore, this study used paleolimnological techniques to assess changes in the water quality of Lake Simcoe over the past ca. 200 years. Sedimentary diatom assemblages were analyzed in 210Pb‐dated cores from five sites across the lake. Diatom assemblages recorded several pronounced and synchronous shifts over the last ca. 200 years. Modest lake‐wide shifts in diatom community composition occurred in the late‐1800’s and early‐1900’s, suggesting that early cultural disturbances, such as land clearance and canal construction, had relatively minor impacts on Lake Simcoe. However, starting in the 1930’s, agricultural and urban development intensified, as indicated by substantial increases in eutrophic taxa. The most pronounced lake‐wide shift in diatom assemblages occurred in the mid‐to‐late 1900’s, the taxonomic nature and timing of which strongly suggest a response to regional climate warming. Moreover, diatom compositional trends at all sites were significantly correlated with instrumental records of regional temperature and lake ice the last ca. 100 years. An additional and marked lake‐wide shift in diatom assemblages occurred in the mid-1990’s, coinciding with the invasion of dreissenid mussels. The combination of stressors acting concurrently on Lake Simcoe, as well as the lake’s distinct water chemistry and size, make it challenging to reconstruct single limnological variables (such as, total phosphorus) in this system. Nevertheless, overall patterns of diatom compositional changes from the five sites revealed the largest shifts occurred in the post‐1950 sediments and that change in lake‐water total phosphorus concentrations played a minor role. Our results imply that substantial changes in climate have amplified the effects of multiple stressors in this complex system. / Thesis (Master, Biology) -- Queen's University, 2010-08-04 12:03:42.267

Te Waihora – Lake Ellesmere is an expansive, shallow, turbid, brackish, hyper-eutrophic, lowland lake located on the east coast of New Zealand’s South Island. The catchment and lake are in a highly modified state, with much of the catchment used for intensive agriculture and the lake’s level artificially controlled by cutting a channel through the barrier separating the lake from the sea. Although it is known that Waihora is highly modified, it is difficult to determine the factors contributing to the current lake state and what constitutes a natural state for this lake. In order to plan management strategies, it is important to have this information. This study aims to provide insight into these matters using paleoecological techniques, in particular, analysis of sediment characteristics, palynology and diatom analysis, on cores obtained from the lake bed. The results of these analyses show that Waihora has had a diverse history, beginning as a freshwater lake, low in nutrients, not long before c. 7500 years ago, following the fusion of Kaitorete ‘Spit’ with Bank Peninsula. This freshwater state was interrupted by the discharge of a large river into the basin, causing a permanent barrier opening and tidal, brackish conditions to prevail. A second brackish state formed after this, caused either by a shift in the discharge point through the barrier or, more likely, a second avulsion event of the Waimakariri River to a discharge point into Waihora. Upon the avulsion of this river to a discharge point north of Banks Peninsula, a freshwater, nutrient rich lake formed. Subsequently, human influenced lake changes became evident, with a hypereutrophic, shallow, brackish lake forming. This research provides evidence that modern lake management has led to decreased lake levels and increasing salinity within Waihora. Intensive agriculture, particularly since the 1970’s has led to an increase in nutrients within the lake and its current hypereutrophic state. A combination of lake level management and the ‘Wahine Storm’ (1968) has led to the lake’s current turbid, phytoplankton dominated state. Therefore, sediment characteristics, palynological and diatom data suggest that a natural condition for the lake is one with lower nutrient levels, lower salinity with greater depth and area than the current lake, with a large distribution of freshwater riparian vegetation and little halophytic vegetation. If restoration of the lake is a target then (1) the lake should be opened to the sea less frequently, allowing a decrease in lake salinity and conditions conducive to the prevalence of freshwater riparian vegetation to prevail, and (2) a transition from a phytoplankton dominated state to a macrophyte dominated state should be targeted, by maintaining the lake at greater depths, the use of riparian planting practices and decreasing nutrient input. However, the latter will be costly and involve questionable trade-offs between lake values and stakeholders. Regardless of whether or not restoration of Waihora to something resembling a natural state is, or will be, a management aim, a decrease in nutrient input catchment wide and riparian planting in the area surrounding the lake should be a priority and may present a more realistic, short term management objective.

Thesis (Ph. D. ), Memorial University of Newfoundland, 1999. / Bibliography: p. 194-217.

Cyanobacterial blooms, such as those recently reported in Great Slave Lake (GSL, NWT), have sparked concern over the occurrence of toxic blooms in the North. This study investigated past and present incidences of cyanobacteria in lakes above latitude 60° N. The abundance of the toxin (microcystin) gene mcyE, as well as genes common to all cyanobacteria (16S rRNA) and bacteria (glnA) were quantified from lake sediment cores using ddPCR. Individual colony isolates from a surface bloom in Yellowknife Bay (GSL) in August 2015 were amplified and identified as non-toxigenic Dolichospermum lemmermannii. Very low levels of microcystin genes were detected through the sediment archives (over ~100-150 yr) of GSL and other lakes, as well as in the plankton of GSL. While recent increases in mcyE were not observed, an increase in the cyanobacterial 16S rRNA and glnA genes was seen through time. In the high Arctic Meretta Lake, gene abundance profiles reflected the effects of past eutrophication and recovery.