Lakes near Sudbury, Ontario, experienced widespread acidification and metal-contamination beginning in the late-19th century. These stressors caused extreme damage to regional aquatic systems and their catchments, with aquatic biota experiencing reduced species richness and, in some cases, extirpations. Emission control measures markedly improved pH, however biotic recovery continues to lag water quality improvements, prompting investigation into mechanisms leading to this phenomenon. Due to the lack of long-term monitoring data, I use paleolimnological approaches to examine temporal trends in cladoceran zooplankton, from pre-impact conditions, through the period of acidification/metal contamination, and following the implementation of emission controls. I assess the degree of biotic recovery that has taken place in these lakes, and review the mechanisms that continue to structure cladoceran assemblages. Lakes closest to Sudbury recorded increases of ~15-65% relative abundance of Chydorus brevilabris, concurrent with the late-1800s industrial development. The relative abundance of C. brevilabris remains elevated above pre-impact levels in two Sudbury lakes; however, in Middle Lake, which was neutralized with calcium carbonate, declines in C. brevilabris (to ~pre-impact levels) occurred following neutralization. Conversely, lakes located ~60 km southwest of Sudbury, in Killarney Provincial Park, experienced muted assemblage change, with minor (< ~5%) increases in grazers (e.g., Daphnia spp., Holopedium glacialis) occurring within the past ~40 years. Lakes in Sudbury and Killarney acidified to pH < ~5, however those in Sudbury additionally received high inputs of nickel and copper, which have toxic effects on aquatic organisms, including some Cladocera. Contamination with these metals may have been a primary driver of cladoceran assemblage change. Elevated metal concentrations likely continue to structure the cladoceran assemblages in the Sudbury lakes. In addition, many of the lakes contain altered food webs (e.g., large populations of yellow perch) as a legacy of the acid and metal contamination, acting as a potential barrier to recovery. Finally, warming air temperatures over the past ~40 years, which I link to increases in primary production, may alter the composition of cladoceran species found in these lakes, and therefore prevent a return to pre-impact conditions. / Thesis (Master, Biology) -- Queen's University, 2014-04-28 12:26:39.903

Due to accelerated climatic warming during the past fifty years, interest and concerns have been growing about changes in the ecological integrity of shallow freshwater ponds that dominate the landscape of the Hudson Bay Lowlands (HBL). Climatic warming is altering the hydrological processes that influence the water balances in these ponds, but knowledge remains insufficient to determine the effects these changes have on ecological conditions in the ponds. To address this knowledge gap, this study examines the relations between current hydrological and limnological conditions and recently deposited sedimentary assemblages of diatoms and photosynthetic pigments in 23 shallow ponds in the HBL. The knowledge from the contemporary studies will be used to inform paleolimnological reconstructions using multiple proxies at two ponds to assess how hydroecological conditions have changed during the past several centuries in response to climatic variations. Water samples were collected three times in 2010 to explore the relations between current hydrological and limnological conditions. The climatic conditions in 2010 provided an excellent opportunity to assess the effects that continued climate warming may exert on hydrolimnological conditions in the study ponds as the warm, dry conditions during the early thaw-season (May- mid-July) followed by extremely wet conditions for the remainder of the thaw-season are likely representative of future climate scenarios. The analysis revealed that the water chemistry in the ponds evolved along one of four different ‘trajectories’ throughout the thaw-season in 2010. These seasonal patterns of limnological conditions closely aligned with similar patterns identified in a study of contemporary hydrological conditions (Light, 2011; Wolfe et al., 2011). The patterns identified in both the hydrological and limnological studies were attributed to differences among ponds in catchment characteristics and hydrological connectivity with adjacent basins. Surface sediment samples were collected in 2010 to determine if hydrolimnological conditions are reflected in the distribution of recently deposited diatom and pigment communities. It was determined that diatom community composition was most highly influenced by the availability of microhabitat in the ponds which did not appear to be controlled by hydrological conditions. Nitrogen availability was determined to be indirectly influencing diatom community composition as the nitrogen-limited conditions in the ponds favoured the proliferation of N2-fixing cyanobacterial mats that provided a large amount of epiphytic habitat in the majority of the study ponds. This resulted in the complete domination of diatom assemblages by one diatom specie that was closely associated with these algal mats in the surface sediments of most ponds. Aphanizophyll, a photosynthetic pigment representative of nitrogen-fixing cyanobacteria, was also in the highest concentration in most of the study ponds as a result of the nitrogen-limiting conditions that allowed these organisms to dominate. Ponds located in the tundra ecozone were also found to have the highest overall pigment concentration which was related to a longer growing season due to the small size of these ponds that resulted in earlier ice-off conditions. The longer growing season of ponds in the tundra ecozone may also be due to high winds that cause a decrease in snow cover, lower surface albedos and an earlier onset of the spring thaw. The paleolimnological reconstruction of two of the ponds revealed similar shifts in diatom community composition in the stratigraphic record even though patterns of past change in their basin hydrology, as explored though the analysis of the δ18OPW record archived in the aquatic cellulose contained in the pond sediments, was very different. The water balance of “Left Lake” was found to be highly influenced by increased evaporation associated with recent warming trends as it is a relatively small basin that becomes hydrologically isolated after the melt period. However, “Erin Lake” was not as susceptible to evaporation during the recent warming trend due to its larger catchment and hydrological connections to other ponds. Both of these ponds experienced marked changes in the diatom assemblages. The changes were characterized by a shift from assemblages containing both small, adnate, benthic taxa that prefer mineral grain substrates and epiphytic taxa that are associated with the cyanobacterial mats covering the pond bottoms to assemblages entirely dominated by epiphytic taxa. The shift in diatom community composition occurred ~1820 in Left Lake, but the timing cannot be determined with any degree of confidence in Erin Lake as no diatoms are observed in the sediment record during the period when the change occurred (~1550 to 1850) due to preservation issues. Analysis of fossil pigments indicates that nitrogen-fixing cyanobacteria have been important to the ecology of the ponds over the entire sediment record. However, there is a trend towards lower concentrations of pigments representative of N2-fixing cyanobacteria in the most recent sediments. The trend in cyanobacterial pigment concentrations coincides with inferred changes in nitrogen availability from the geochemical analysis of the pond sediments by Light (2011). This recent shift in nutrient status may be the result of a number of factors including the increased atmospheric deposition of anthropogenically-derived nitrogen or changes in biogeochemical cycling in the ponds.

This study examined if nutrient loading of phosphorus-rich pollen into small mountain lakes has a significant impact on lake productivity. Increased pollen input into lakes due to changes in vegetation (e.g., timberline advance) may increase lake production. Deteriorated pollen was recorded for frozen and freeze-dried sediment samples to determine if storage method effects pollen preservation. There were no strong relationships between pollen accumulation rates (PAR) and pigment concentrations for Sentinel Lake and Eiffel Lake. A lagged response of pigment concentrations to increased PAR was illustrated for Eiffel. Examination of pollen ratios and stomata suggests recent timberline advance for Eiffel, but pollen ratios were a poor indicator of timberline for Sentinel. Sediment storage methods did not play a significant role in differential preservation of pollen grains. Further investigation of the potential effect of PAR on lake productivity is required because timberline advance may alter lake productivity through increased pollen input. / Ecology

Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 101-111).

No description available.

Despite lake sensitivity to climate change, few Florida paleolimnological studies have focused on changes in hydrology. Evidence from Florida vegetation histories raise questions about long-term hydrologic history of Florida lakes, and a 25-year limnological dataset revealed recent climate-driven effects on Lake Annie. The objectives of this research are (1) to use modern diatom assemblages to develop methods for reconstruction of climatic and anthropogenic change (2) to reconstruct both long-term and recent histories of Lake Annie using diatom microfossils. Paleoenvironmental reconstruction models were developed from diatom assemblages of various habitat types from modern lakes. Plankton and sediment assemblages were similar, but epiphytes were distinct, suggesting differences in sediment delivery from different parts of the lakes. Relationships between a variety of physical and chemical data and the diatoms from each habitat type were explored. Total phosphorus (TP), pH, and color were found to be the most relevant variables for reconstruction, with sediment and epiphyte assemblages having the strongest relationships to those variables, six calibration models were constructed from the combination of these habitat types and environmental variables. Reconstructions utilizing the weighted averaging models in this study may be used to directly reveal TP, color, and pH changes from a sediment record, which might be suggestive of hydrologic change as well. These variables were reconstructed from the diatom record from both a long-term (11,000 year) and short-term (100 year) record and showed an interaction between climate-driven and local land-use impacts on Lake Annie. The long-term record begins with Lake Annie as a wetland, then the lake filled to a high stand around 4000 years ago. A period of relative stability after that point was interrupted near the turn of the last century by subtle changes in diatom communities that indicate acidification. Abrupt changes in the diatom communities around 1970 AD suggest recovery from acidification, but concurrent hydrologic change intensified anthropogenic effects on the lake. Diatom evidence for alkalization and phosphorus loading correspond to changes seen in the limnological record.

This thesis focuses on a chronological analysis of the cladoceran communities from a sediment core of a small oligotrophic lake in southwestern Québec, Canada over the past 1250 years. The sediments of the lake were varved, which allowed for accurate dating. A previously published pollen study of the lake provided a record of the paleoclimatic and landscape changes in the region. The core was then used to infer how changes in temperature and landscape changes impacted the taxonomic composition of the cladoceran community through time. Cladoceran diversity was high throughout most of the Medieval Warm Period and into the Little Ice Age and decreased during the modern period in response to increased temperatures and anthropogenic impacts. Daphnia and plant-associated species greatly decreased in the past 100 years. This shift, combined with increased temperatures and changes in the landscape opened up a niche for the colonization by the smaller Bosmina longirostris. The modern communities are unlike most of what was observed throughout the past millennium.

No description available.

In-situ oil sands operations have been the dominant method of bitumen extraction in Canada since 2012; however, research on contaminants attributed to this method is limited in the peer-reviewed scientific literature, compared to that of open-pit mining. The Cold Lake oil sands region operates using exclusively thermal in-situ extraction techniques, raising the issue of whether oil sands activity is resulting in petroleum hydrocarbon (PHC) contamination in the absence of open-pit mines, upgraders, refineries, tailings ponds, and other bitumen processing operations. The lack of baseline contamination levels prior to oil sands development hampers debate on contamination from the oil sands industry. We address this shortcoming by using regional lake sediment cores to characterize petroleum hydrocarbons and trace their origin within the Cold Lake oil sands deposit. Petroleum hydrocarbons are hydrophobic compounds that bind to sediments, therefore persisting and accumulating in aquatic environments. This thesis examines historical levels of polycyclic aromatic hydrocarbons (PACs), petroleum biomarkers, and n-alkanes in radiometrically dated sediment cores collected from the depocenter of lakes within the Cold Lake heavy oil field. We used alkylated PACs and a suite of petroleum biomarkers to evaluate in-situ operations as potential petroleum-derived contamination sources. We predicted that similarly to open-pit mining, concentrations of PHCs in lake sediments would increase with industrial activity corresponding to proximity from in-situ operations. Like open-pit regions, alkylated PACs in Cold Lake sediments were elevated when compared to unsubstituted parent PACs and were significantly enriched in lake sediments deposited after the onset of oil sands operations. These findings imply that in-situ oil sands activity is driving the enrichment; however, diagnostic ratios and pyrogenic indices confirm a strongly pyrogenic origin in both pre-industrial and more recent sediments. When compared to a Cold Lake bitumen sample, the principal components driving PHC enrichment do not resemble bitumen. Likewise, diagnostic ratios of petroleum biomarkers and n-alkanes do not support bitumen as a significant source of hydrocarbons. PHC inputs in lake sediments are instead from terrestrial vegetation and plant waxes. These findings suggest that bitumen is not significantly contributing to petroleum hydrocarbon enrichment to lakes within the Cold Lake oil field; however, emissions from in-situ activity (natural gas burning, diesel trucks, seismic line cutting etc.) is increasingly abundant in more recent sediment. With >80 % of Canadian bitumen reserves requiring in-situ techniques for extraction, this thesis provides the first assessment of the spatial and temporal relationship between contaminant loading and proximity to in-situ oil sands operations. Additionally, this study allows for the environmental implications of open-pit mining operations to now be compared to that of in-situ techniques.

The aim of this study was to work out whether bloomery activities might have left a geochemical imprint in two mires close to a known bloomery and identify differences between the geochemical signals in the mires. Therefore two peat profiles (140 cm deep) and a series of bulk samples (composite of 10-60 cm) were taken near the remains of a bloomery close to Ängersjö, Hälsingland, which has one documented radiocarbon date of AD 1300-1435. One profile was taken in the fen closest to the bloomery, the other profile was taken close to a nearby lake. Geochemical analysis of the peat samples was performed with X-ray fluorescence spectroscopy (XRF). The results were combined with previously taken data from a sediment profile from the lake ~120 m away and a pollen profile close to the bloomery. The results showed that the activities of the bloomery were visible in the geochemical signals of the peat core closest to the bloomery with two peaks in Pb and Zn, which coincide with the previous reported times of operation (1. AD 1030-1060; 2. AD 1300-1435), which also fits with the pollen record from the nearby peat record. The mire close to the lake, which is hydrologically not connected with the area where the bloomery was, did not show these increases in elements associated with iron processing and only a small peak of Pb was visible. Furthermore, the geochemistry of the bulk samples showed that a disturbance of the mire surrounding the lake was responsible for the geochemical changes observed in the lake,particularly as a source of increases in inferred biogenic Si observed in the sediment record (as increased Si/Al ratios) in association with human-related disturbance in the sediment record during AD 800-1200. Si concentrations in the bulk peat samples in the fen adjoining the lake range as high as 14% (≤23% as SiO2).