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Surface water quality is a dynamic quantity to deal with. There are factors which affect the surface water quality. These factors include weather changes, anthropogenic activities and urbanization. There is an underlying problem with water quality monitoring and management around the world especially in developing countries. Pollution outbreak in a Luton town lake in 2012 which killed a lot of fishes is one instance of such devastating outbreak and the underlying effects. This thesis is aimed at utilising measured data values for certain physico chemical parameters in the determination of surface water quality through analysis, indexing and model prediction. The physical parameters measured are temperature, conductivity and turbidity while the chemical parameters are dissolved oxygen, pH and ammonium. These parameters are measured at two locations on the Luton Hoo Lake which is used as our research study site to monitor the water quality and possible sources of contamination. Data with regards to the values of the different parameters is collected with the help of multi parameter probe sensors that were installed at the site in form of a remote monitoring station. Manual sampling of the water and collection of parameter value readings is also used to substantiate the values derived from the remote monitoring stations. A preliminary analysis is carried out using descriptive Statistics and correlation analysis to determine the dependencies between the various parameters measured for water quality monitoring. We evaluate the relationship of the measured parameters to contamination sources and its impact on the water quality as it affects aquatic life. With the correlation analysis, it is discovered that some of the parameters exhibited the expected relationship whereas some could not relatively show any dependence. This led to the need for further analysis to help in the parameter selection since the aim of this work is to use minimal parameters to establish the water quality status. It is determined that dissolved oxygen is the most important parameter compared to other measured parameters. This was actualized through the use of principal component analysis to identified the major components. Multiple linear regression is used to establish the relationship between Dissolved oxygen and the other measured parameters. The two locations being monitored exhibit the same trend from the results of the box plot analysis that was carried out. Dissolved oxygen is inversely proportional to Temperature which confirms the same trend pattern as exhibited by the correlation analysis. Principal component analysis helps in the establishment of the hierarchy of the parameters measured and the level of importance which determines the input parameters for the water quality index. This research work looked at various water quality indices developed by various researchers and discovered that most available indices were limited by the fact that the data collection was done manually. This work adopted the use of a tailored Water quality index with three parameters which are Dissolved oxygen, Conductivity and Turbidity. These parameters were selected based on the results derived from the Principal components analysis. Water quality index is a good way of uniquely rating the overall water quality status of a water body using a single term. In this research study, we utilised available water quality indices that have been developed through expert opinions and modified them to suit our requirements. The results obtained were satisfactory and proved that the use of minimal parameters can give a good indication of the water quality in same way as the use of many parameters. The minimal Water Quality Index is recommended where faster and more economical approach is needed in decision making with regards to water quality monitoring. A hybrid neural network is finally proposed for the prediction of parameters for water quality index which can be tailored based on the location of the surface water and the primary use of the surface water for the end users. The major problem of identifying a low cost way of monitoring surface waters for developing countries is achieved through the use of minimal parameters and the availability of the sensor probes in the market is of great importance to the work.

Terrestrial inputs of organic matter contribute greatly to the functioning of aquatic ecosystems, subsidizing between 30-70% of secondary production. This contribution of terrestrial resources is especially important in boreal lakes that are largely nutrient-poor and thus more responsive to these additions. Yet the mechanisms underlying initial processing of terrestrial resources by microbial communities at the base of lake food webs remain poorly understood. With this in mind, this thesis aims to advance our understanding of lake sediment microbial community assembly and functioning along abiotic gradients, primarily reflecting variation in terrestrial organic matter inputs that are predicted to increase with future environmental change. Chapter 1 reviews current knowledge on the terrestrial support of lake food webs and highlights gaps in understanding the factors influencing the microbial processing of terrestrial resources. It also provides an overview of metagenomics methods for microbial community analysis and their development over the course of the thesis. Chapter 2 tests how much of ecosystem functioning is explained by microbial community structure relative to other ecosystem properties such as the present-day and past environment. Theory predicts that ecosystem functioning, here measured as CO2 production, should increase with diversity, but the individual and interactive effects of other ecosystem properties on ecosystem functioning remain unresolved. Chapter 3 further questions the importance of microbial diversity for ecosystem functioning by asking whether more diverse microbial communities stabilize ubiquitous functions like CO2 production and microbial abundances through time. It also aims to identify the biotic and abiotic mechanisms underlying positive diversity-stability relationships. Chapter 4 then explores how microbial communities assemble and colonize sediments with varying types and amounts of terrestrial organic matter in three different lakes over a two-month period. Understanding how microbial communities change in relation to sediment and lake conditions can help predict downstream ecosystem functions. Finally, Chapter 5 discusses the main findings of the thesis and ends with proposed avenues for future research.

The estimated global production of red mud, a by-product of alumina production, is ~120 million t per year. Little is known about the long-term chemical, physical and ecological responses in aquatic ecosystems following pollution with red mud. To date, no whole-lake assessment of the impact of red mud and recovery trajectories has been conducted. Kinghorn Loch, Fife, Scotland, is an important example of a red mud polluted aquatic ecosystem. This is due mainly to the availability of long-term data documenting changes in the lake during the pollution and recovery following diversion of red mud leachate in 1983 to date. Long-term data were assessed to determine the time scale of recovery for a range of specific pollutants in the surface waters of Kinghorn Loch, and field surveys and a laboratory controlled experiment were conducted to investigate lake sediment-pollutant interactions and arsenic (As) species bioaccumulation in aquatic plants. Results showed recovery of the lake water column, with a significant decrease of pH and the concentrations of all red mud constituents in surface water since the cessation of pollution. Using generalised additive models the chemical recovery period was 5 years for pH and from 22 to 26 years for As, vanadium (V) and phosphorus (P), with aluminium (Al) still not reaching the end-point recovery following this period. A 12- month field survey showed that concentrations of phosphate (PO4-P), total phosphorus (TP), dissolved and total As and V in lake water varied significantly throughout the year, with depth of overlying water contributing to variation in P concentrations in water above sediment. A range of physico-chemical factors, including dissolved oxygen (DO), pH and concentrations of pollutant binding element controlled seasonal and spatial variations in water column contaminant concentrations. The behaviour of V differed from As and P concentrations in water, with maximum V concentrations occurring in spring and the highest concentrations of As and P in surface water and dissolved As and PO4-P in water above sediment observed in summer. With the exception of V in deeper layers of the water column in spring and winter, observed total As and V concentrations met standards for Protection of Aquatic Life in the UK (50 and 20 μg L-1, respectively). Sediment in Kinghorn Loch is still contaminated 30 years into the lake recovery period. The highest seasonal mean concentrations in the upper (0-4 cm) sediment layer were 231 mg kg-1 for V and 185 mg kg-1 for As, the latter considerably exceeding Canadian Sediment Quality Guidelines for the Protection of Aquatic Life for As (17 mg kg-1). Evidence from the laboratory experiment and the field observations suggests that the lake still processes red mud contaminants, with seasonal mobilisation of As and P from lake sediment under reducing conditions. In contrast, release of V from sediment into overlying water appeared not to be driven predominantly by redox conditions, but instead by interactions between pH, competitive ion concentrations and DO. Higher pollutant concentrations observed throughout the year in deeper layers of the water column compared to surface water indicated that the impact of sediment on the water column is generally confined to the bottom waters of the lake. Macrophytes in Kinghorn Loch contained relatively high concentrations of As, predominantly in the inorganic form which is most toxic to organisms. The highest As content measured in roots of Persicaria amphibia (L.) Gray (40.4 – 218 mg kg-1) greatly exceeded the 3 – 10 mg kg-1 range suggested as a potential phytotoxic level. Accumulation of toxic As species by plants suggested toxicological risk to higher organisms in the food web and indicated that ecological recovery of the lake is still in progress. The results of this research at Kinghorn Loch will help water resource managers to understand not only the environmental and human health effects of multiple pressures related to red mud pollution, but also the likely recovery time scales in relation to water quality targets.

There is little doubt that anthropogenic climate change will have long lasting, unavoidable, large scale and cross sector effects. Having a clear understanding of the scale and rate of projected future changes, and the potential impacts of those changes at multiple spatial and temporal scales, will be important to allow environmental managers the best chance of adapting to changing conditions. There are particular concerns about impacts on freshwater systems due to the coupling of direct impacts to both hydrology and ecology. Expected changes can be grouped into three functional categories: those affecting physico-chemical (broadly water quality), hydromorphological (physical structure and habitat) and biological elements of the lake system. The Lake-Landscape Context framework provides a way of approaching the sensitivity or resilience of an individual lake to change by exploring the complex and multi-layered relations between water, land and human activity. However, the exact combination of strategies and actions available to environmental managers is yet to be comprehensively documented beyond broad principles. To reach this goal, to manage our ecosystems in the most comprehensive and responsible way, we need to have a clear understanding of what and where that resource is, what the conservation priorities currently are and where threats to these priorities are likely to emerge. Therefore, the overall aim of this thesis was to develop adaptation strategies to minimise climate change impacts on the conservation interests of Scotland’s standing freshwater. This was approached through the adoption of the ESVRA conceptual framework, intended to assist policymakers and practitioners in adaptation planning. Practical actions can be guided by working through the framework’s four key stages: understanding exposure to the pressure (external drivers); considering the sensitivity and resilience of the system at multiple scales (internal functions); exploring areas of vulnerability (a measure of sensitivity plus exposure); and consideration of multiple possible responses across spatial and temporal scales. Chapter 2 explores the lake resource making use of the latest geospatial data and GIS techniques to investigate Scottish standing freshwaters in depth. 5,165 Scottish lakes exhibit an outstanding myriad of forms and sizes ranging across the country. This variety of form, density and distribution contribute to habitats of international importance for numerous species. Perhaps because of this diversity, no natural grouping of lakes were found based on simple hydromorphological categorisations. The use of landscape and wildness ‘scoring’ is a novel geographic approach, which may be an important factor in how landscapes are valued in the future. Chapter 3 investigates the direct exposure to global climate change facing Scotland. Projected changes to global climate were downscaled to illustrate impact on the UK and Scotland using both the UKCP09 and HadGEM2-ES climate models. Climate change by the 2050s will impact the UK in the range 1.1°C to 2.7°C with a clear South-East/North-West gradient. Precipitation too is projected to change in the UK in this time, with annual precipitation varying from -65 to +116 mm/yr. By incorporating the climate model data into a GIS it was possible to further interrogate the results for specific locations, with a detailed water balance model created for all 5165 lakes. This model suggests that during the summer months there will be sustained periods of water scarcity and deficit. Finally, in this chapter, a climate change spatial risk assessment was undertaken, identifying 200 lakes in the area of greatest projected change. Leading on from these findings, Chapter 4 explores the vulnerability of Scotland’s standing freshwaters. A vulnerability framework attempts to place resilience as a key part of the model, which has to date been missing from similar assessments. The expert weighted scoring mechanism highlights 851 of Scotland’s standing freshwaters, geographically spread across the country, as being highly vulnerable to projected climate changes. The results were mapped to show the vulnerability across Scotland and a display system for individual lakes proposed that allows a transparent and coherent structure that can shed light on distinct components of vulnerability, so that each can be evaluated individually, and in combination. Finally, in Chapter 5, a multipart online survey with key stakeholder experts actively involved in freshwater environmental management was produced to approach adaptation strategies and actions themselves. Over 80 adaptation actions specifically applicable to Scotland’s standing freshwaters were collated and grouped into 12 adaptation strategies. All 12 strategies were considered desirable with six strategies considered ‘Definitely feasible’, a further four considered ‘Likely feasible’. This provides a framework of potential actions that could help to reduce system sensitivity by increasing adaptive capacity or system resilience. In conclusion, while there are undoubtedly challenges ahead for Scotland’s standing freshwaters and for those who manage them, there is clear opportunity to make proactive and engaged decisions to minimise the impact of climate changes on the conservation interest of these important habitats.

Dissolved oxygen concentrations are declining in the bottom waters of many lakes around the world, posing critical water quality concerns. Throughout my dissertation, I assessed how bottom-water dissolved oxygen may mediate the effects of climate and land use change on water quality in lakes. First, I characterized causes of variation in summer bottom-water temperature and dissolved oxygen. I demonstrated that spring air temperatures may play a greater role than summer air temperatures in shaping summer bottom-water dynamics. I then characterized the effects of declining bottom-water oxygen concentrations across diverse scales of analysis (i.e., using microcosm incubations, whole-ecosystem oxygenation experiments, and data analysis of >600 widespread lakes). I found that low dissolved oxygen concentrations contributed to release of nutrients and organic carbon from lake sediments, potentially altering the role of lakes in global biogeochemical cycles. Importantly, I also found support for a previously-hypothesized Anoxia Begets Anoxia feedback, whereby bottom-water anoxia (i.e., no dissolved oxygen) in a given year promotes increasingly severe occurrences of anoxia in following summers. This finding demonstrates the need for forecasts of future oxygen dynamics in lakes, as management actions to preempt the first occurrence of anoxia will be more effective than actions to restore ecological function after oxygen concentrations have already declined. To build the capacity for such forecasts, I led a systematic review of ecological forecasting literature that characterized the state of the field, emerging best practices, and relative predictability of four ecological variables. Combined, my dissertation provides a mechanistic examination of the effects of climate change on water quality in lakes worldwide, ultimately helping to anticipate, mitigate, and preempt future water quality declines.

This thesis looks into the use of historical macrophyte records to assess long term changes in macrophyte communities in lakes and potential reasons for these changes. In particular it uses historical records to assess changes in macrophyte communities in the Norfolk Broads and West Midland Meres, two sets of lowland, eutrophic lakes in England. It provides a critical examination of the use of historical records, highlighting some of the constraints common to such data such as variations in recording effort, and bias in species recording and site selection. Having acknowledged these issues we then go on to develop a robust way to interpret such data, using a “change index” based on species persistence over the last 200 years within individual lakes. Species with high change index values, which represented species which had persisted or increased within the lake districts, were those known to be characteristic of eutrophic lakes. Conversely species with low index scores, which had declined in both the broads and meres over the last 200 years, included species associated with less fertile conditions but also a selection of typically eutrophic species. Averaging of change index scores in present day survey data served to identify the historically least changed lakes and to rank lakes in order of degree of botanical change over the last century. We then analysed the ecological basis of the change index in order to better understand the processes behind the decline of some species and survival of others in the Norfolk Broads and West Midland Meres. Functional groups determined from morphological and regenerative traits displayed significant differences in change index values in both groups of lakes, but declining taxa occurred across a wide range of plant growth forms. Non-hierarchical clustering of species based on their ecological preferences, obtained from published literature, resulted in groups with distinct change index values, indicating that changes in the status of species could be partly explained by these preferences. Of these, trophic preference was consistently the most important, with species of less fertile habitats consistently experiencing the greatest declines. However, some characteristically eutrophic species have also declined significantly, particularly in the broads. In these cases increasing loss of shallow water, low energy habitats in the broads, or loss of fluctuating water levels and less alkaline backwaters in the meres, appear to have been contributory factors. In addition to the change index approach, we also used historical records at a site level to complement palaeolimnological analysis and investigate the change in macrophyte community composition and structure at Barton Broad, Norfolk. Sediment samples were extracted from the bottom of the broad and analysed for sub-fossil remains and pollen of macrophytes. The historical records and palaeolimnological analysis combined showed that early communities did not consist entirely of low growing, oligotrophic and mesotrophic species as previously thought, but in fact comprised a mixture of these and other more characteristically high nutrient species associated with taller, or free-floating growth habit. As eutrophication progressed throughout the last century, the community was increasingly dominated by these latter growth forms. Diversity was maintained, however, since encroaching reedswamp generated a mosaic of low energy habitats which supported a range of species unable to withstand the hydraulic forces associated with more open water habitat. When the reedswamp disappeared in the 1950s, many of the dependent aquatic macrophytes also declined resulting in widespread macrophyte loss. The thesis demonstrates not just the complexities of using historical records, but also ways in which these can be overcome to make useful observations about macrophyte community change and lake ecological integrity to inform conservation and lake management, both on a site and lake district level.

Microbes, living on the boundary between the sediment and the water-column in lakes, can play a pivotal role in governing the magnitude and frequency of nutrient cycling. The purpose of this research was to focus on the role of benthic microalgae in regulating such processes and to identify spatial and temporal characteristics in their function. Approaches included the quantification of sediment nutrient concentrations (particularly P fractionation), estimates of equilibrium phosphate concentrations (EPC0) (resuspended and undisturbed sediment estimates), and assessment of the benthic microalgal community composition, biostabilisation capacity, and its ability to regulate diffusive-nutrient flux. This thesis highlighted the importance of biological regulation of benthic/pelagic nutrient cycling, especially the role of benthic microautotrophs. Release sensitive sediment-P fractions were observed to be highly variable (both with depth and season) and correlated well with indicators of benthic photosynthesis (e.g. DO, chlorophyll, pH). Understanding the seasonality of whole-system P partitioning can enhance future lake management programmes. EPC0 estimates were significantly higher during undisturbed as opposed to disturbed sediment conditions. Epipelon constituted < 17 % of the total sediment chlorophyll signal and was highest in the clearer winter months and at intermediate depths at which a trade off between wind-induced habitat disturbance and light limitation existed. In intact core experiments, the benthic microalgal community significantly reduced the diffusive nutrient (especially PO₄-P and SiO₂) flux. NH₄ -N release was highest under light conditions at high temperatures. The mechanisms for regulation included direct uptake, photosynthetic oxygenation of the sediment surface, and regulation of nitrification/denitrification processes. Sediment stability increased with colloidal carbohydrate concentration (extruded by benthic microbes) at 4.1 m water-depth but not at 2.1 m overlying water depth, probably indicating the role of habitat disturbance in shallow areas acting to reduce epipelic production. Additionally, in an ecosystem comparison, the nature and extent of the biotic mediation of sediment stability varied between freshwater and estuarine ecosystems.

Abstract: Ongoing permafrost thaw in northern peatland catchments may increase the production and downstream delivery of neurotoxic methylmercury (MeHg) across the terrestrial-aquatic continuum. Peatlands in boreal-Arctic regions have large stocks of mercury (Hg) in frozen soils, accumulated through atmospheric deposition of natural and human-emitted Hg over thousands of years. Permafrost thaw in peatlands often leads to land surface collapse (thermokarst), which may shift environmental conditions to facilitate microbial production of MeHg (methylation). However, the degree to which Hg is methylated post-thaw and exported downstream remains uncertain in northwestern Canada and poses a potential hazard for uptake by aquatic food webs. I initiated three field studies examining MeHg cycling throughout the peatland-rich Interior Plains of boreal western Canada – 1) examining how peatland and permafrost extent influenced MeHg concentrations through a synoptic sampling of lakes and streams, 2) determining how discharge and land cover controlled the export and concentrations of MeHg in two stream catchments with differing peatland extent, and 3) exploring the microbial production of MeHg in thermokarst wetlands compared to intact permafrost peatlands. By sampling total Hg (THg) and MeHg concentrations from 25 lakes and 47 streams spanning 1700 km across the Interior Plains (Chapter 2), I found that peatlands were primary sources of MeHg to surface waters regardless of permafrost extent, as MeHg concentrations increased with indicators of peatland-derived water chemistry. Lakes were potential MeHg sinks, likely through solar MeHg degradation (photodemethylation), while resident microbial communities in lake sediments were most capable of gaseous Hg emission to the atmosphere rather than methylation. To consider seasonal variation in MeHg concentrations and export, I initiated a study involving higher-frequency sampling of streams in the discontinuous permafrost region. Alongside Dehcho-Aboriginal Aquatic Resources and Ocean Management, I monitored one peatland-dominated catchment and one mixed catchment of mountains, forests, and peatlands over three years (Chapter 3). Compared to the mixed catchment, the peatland catchment had higher MeHg and lower THg concentrations and greater inter-annual variability in solute yields driven by storage thresholds in peatlands that control runoff generation. Transport limitation primarily controlled solute concentrations in the mixed catchment, with terrestrial flushing during high flows and lower inter-annual variability of solute yields due to consistent streamflow from groundwater sources and runoff generation from steeper slopes. I then studied biogeochemical controls on Hg methylation in peatlands due to their significance as downstream MeHg sources (Chapters 2, 3). From methylation assays and peat and porewater chemistry of twelve peatland sites in the Interior Plains (Chapter 4), I found thermokarst wetlands to have greater methylation potential than intact permafrost peatlands. The highest MeHg concentrations and potential methylation rates were observed in fens and associated with a higher water table, labile organic matter, pH, and concentrations of sulfur and iron. The continued thawing of permafrost peatlands and expansion of thermokarst wetlands will likely result in favorable conditions for MeHg production. My findings suggest that permafrost thaw in northern peatlands will enhance Hg methylation across the landscape, although wetland trophic status and groundwater connectivity will control MeHg production, and catchment hydrological functioning will determine downstream export. This knowledge is important for public health planning and land use intervention in the face of climate change, given the high risks of MeHg in aquatic ecosystems to northern communities.

Hypoxia is a significant source of winter mortality for freshwater fish in north-temperate lakes and has the potential to alter fish communities. A multi-year dataset on Buckskin Lake, a shallow, productive drainage lake in northern Wisconsin with a history of winterkill, allowed the investigation of the effects of periodic winter hypoxia on fish communities. An aeration system was installed in 1984, which raised winter oxygen levels to levels sufficient for higher fish survival. In the winter of 2007-2008, the aerator system failed, causing an extensive winterkill. The lake was sampled from 2002-2005, before the aerator failure, and in 2008-2009, after the winterkill event. In addition, 16 similar lakes in the area with no winterkill history were sampled using similar methods. Using the combined datasets, two hypotheses were tested with non-metric multidimensional scaling (NMDS) and PERMANOVA analyses. We hypothesized that (1): after 18 years of aeration, the Buckskin Lake fish community from 2002-2005 would be similar to the non-winterkill lakes due to the recolonization of species from connected lakes, and (2): the fish community changed significantly in the lake due to the 2007-2008 winterkill event. The first hypothesis was not supported, as NMDS and PERMANOVA analyses showed that Buckskin Lake retained a fish community distinct from the non-winterkill lakes. Our findings were consistent with the second hypothesis: an incomplete winterkill occurred in 2007-2008 due to lack of aeration, causing changes in fish abundances, including the reduction of game fish species and centrarchids, with no notable extinctions. Together, our findings indicate that winter aeration may improve gamefish survival and allow lakes with winterkill tendency to support sport fish communities with healthy piscivore populations such as walleye and largemouth bass, which would be otherwise greatly reduced.

The recent recovery of a core in Unaweep Canyon, Colorado, penetrated ~140 m of lacustrine sediment of what is here termed paleo-Lake Unaweep. The lake is inferred to have formed as a result of mass wasting that blocked the ancestral Gunnison River during the early Pleistocene, causing partial filling of Unaweep Canyon before the ancestral Gunnison River abandoned the canyon. This core has been correlated to previous core that also penetrated paleo-Lake Unaweep, and captures a sediment record that dates from ~1.4-1.3 Ma, enabling a glimpse of the Early Pleistocene before the mid-Pleistocene transition— a time interval rarely captured in an upland (or any) setting of the greater Rocky Mountains. The lacustrine section begins atop an interval of ~21 m of inferred ancestral Gunnison River gravels, and comprises a series of mass flows that, overall, decrease in thickness (2 to 60 cm) from the bottom to the top of the core. The entire lacustrine section exhibits an alternation of two intervals: one exhibiting an olive-gray color and containing siderite, and intervals exhibiting red and ochre colors, possibly recording climatic variations. The basal ~20 m consists of reddish-brown, graded (granules to fine sand) mass flows. Above this is a ~15 m interval of thinner (2-10 cm) and finer-grained mass flows exhibiting ochre colors with pink/white clay caps. Next is an olive-gray interval (~48 m) with mass flows exhibiting basal loading, convolute bedding, sand injections, and mud clasts with thin (

Glaciers do not exist in isolation: they interact with the surrounding Earth System across a wide range of temporal and spatial scales. Global glacier recession driven by anthropogenically forced global warming has both intensified many of the interactions between glaciers and their surroundings and highlighted their importance. Glacier-ocean interactions are one well-known and globally important example, considering that unstable marine-terminating portions of Greenland and West Antarctica hold several metres of potential sea-level rise. However, other important interactions, such as between glaciers and ice-contact lakes, remain largely unexplored. Likewise, a wide suite of connections between glaciers and the surrounding Earth System can influence, and are impacted by glacier change. This thesis explores these interactions with the objective of contributing to a new integrated view of glaciers in the Earth System. The twenty-first century has both highlighted the need to understand glacier retreat and provided scientists with powerful new tools to analyze our cryosphere. In this thesis, I assess the drivers of glacier change by combining high-resolution satellite imagery, lake sediment cores, and field data with numerical modelling. Southern Patagonia is an ideal natural laboratory to examine the interactions between glaciers and the surrounding Earth System, due to its extensive glaciation, high relief, large proglacial lake systems, and extreme climate gradients. We also include two other study locations, the Northern Andes and Uttarakhand Himalaya, in which glacier change has created new geohazards and water security challenges for nearby populations. We find that large ice-contact lakes preserve an high-resolution record of climatic and glacial changes. We identify annual-resolution sediment layering ('varves') in Lago Argentino, the world's largest ice-contact lake, and use this to investigate the dominant controls on sedimentation across the lake. We show that, at Lago Argentino, varves are formed due to seasonal variations in glacial and fluvial sediment fluxes along with a seasonal cycle in lake mixing. In addition, we demonstrate that the dominant climatic controls on sedimentation are summer temperature and wind speed. On a larger scale, we use Lago Argentino's sedimentary record to identify a high late-Holocene eruption rate at the nearby Andean Austral Volcanic Zone, and dominant 200, 150, and 85 year periodicities in the high-latitude Southern Hemisphere's dominant mode of climatic variability, the Southern Annular Mode. Next, we investigate the interactions between glaciers and two major natural hazards: landslides and volcanic eruptions. For the former, we show that landslides can induce extensive and long-lasting effects on glaciers, with a 0.25 km^3 landslide reversing the multi-decadal retreat trend of a Patagonian tidewater glacier. For the latter, we identify a ~75% greater eruption rate in times of low ice volume in Southern Patagonia, due to deglaciation-induced tensional upper-crustal stresses. This process may affect other ice-clad volcanoes around the world. Glaciers can also contribute to major disasters, of which the deadly Chamoli rock-ice avalanche in February 2021 is a devastating example. We combine several advanced remote sensing methods to investigate the pre-collapse conditions of this avalanche, and show that the landslide was mobile more than five years prior to its February 2021 collapse. We also use a newly developed glacier velocity-based method to calculate the thickness and volume of all glaciers in the Northern Andes, where volcano-ice interactions initiated the worst volcanic disaster of the past 100 years. These ice-thickness maps will enable future research to identify zones most vulnerable to glacier-related hazards, and map out future water-resource vulnerabilities. Overall, our results highlight the importance of integrative and collaborative studies for forecasting the future of the world's glaciers, and their impacts on nearby populations.

Lakes are unique in the land surface due to their well-known anomalous intrinsic properties – unusually large heat capacity, stark albedo contrast with water’s phase change and sun’s position. They also exhibit a wide spectrum of extrinsic properties – related to their occurrence, distribution and abundance. That they are ubiquitously besprinkled over most land surfaces with such intrinsic (extrinsic) anomalous (spectrum of) properties makes them a low-hanging fruit to observe from space and tease out in-land climate change signatures from local to global scales. In this dissertation, I explore four aspects in our current understanding of lakes and their connection to climate change, and I show that: 1) Long-term lake changes are multi-directional in nature as a rule and not exception; 2) Lake evaporation calculations using global data can be improved by ~5% at seasonal scales and ~50% (i.e. 5-10X better) in the energy gap to turbulence scales (i.e. ~30 minutes), compared to 5 other state-of-the-art mass-transfer methods, by virtue of a century-old misunderstood body of work by Robert E. Horton that is based on kinetic theory of gasses; 3) Long-term trends can be separated from correlation noise up to 1-sigma better than current practice in terms of both statistical power and confidence by combining a portfolio of 16 methods from two families of trend detection tools from Econometrics (parametric) and Hydrology (non-parametric); 4) Building upon the results of 1-3, a quasi-analytical water albedo model, and derived lake and climate variables from many sources (including Google Earth Engine datasets) can help us characterize lake changes up to sub-daily and sub-meter (micro-topography) scale, under the assumption of regional hydro-climate homogeneity at 0.25 degree spatial resolution (an unavoidable caveat governed by rain gauge density) for millions of Arctic Boreal Zone (ABZ) lakes. Collectively, these results I demonstrate at continental scale spanning whole of Canada and Alaska, ~10 million lakes, carve a pathway for a high-fidelity understanding of local-to-global scale climate change signatures on ~100 million lakes, which are, due to their intrinsic and extrinsic characteristics, our best in-land sentinels of climate change.

This study explores the movement of simulated neutrally buoyant drifters in far western Lake Superior. It was motivated by a desire to understand the transport and fate of microplastic particles originating near the region’s population centers and their potential impact on the Apostle Islands National Lakeshore. Particle movements were determined using the Finite Volume Coastal Ocean Model (FVCOM) configuration developed by the Large Lakes Observatory at the University of Minnesota Duluth. When exploring vertically averaged monthly output for the years 2015 and 2018, particles (which could include microplastic particles or suspended sediments) were modeled as passive drifters and advected using model output during each month. Exploring month- long and three month-long model runs showed that drifters originating in the St. Louis and Nemadji estuaries move predominantly towards the Apostle Islands. Drifters are also predicted to be more prevalent on the northern side of the Apostle islands. Drifters were also observed to travel faster in the late summer months, with more drifters entering and staying in the Apostle Islands during those months as well. The drifter tracks suggest that if a microplastic or other neutrally-buoyant particle is deposited inside of the estuary, assuming no large wind events, it will most likely end up in the Apostle Islands within 3 months, especially during the late summer months. The results of this analysis will help researchers to better understand the source, transport and fate of microplastics in Lake Superior. Part of this research was intended to aid in further understanding microplastic sampling research done in the Apostle Islands during June through December of 2015 (Whitmire et al 2017), and May and August of 2018 (Minor et al 2020).

This thesis presents an outcrop-based, near depositional-strike cross section of fluvio-lacustrine interactions along the well-studied Nine Mile Canyon near Helper, Utah, highlighting the strike variability of facies and depositional environments in the Sunnyside Interval fluvio-lacustrine deposits. We utilize a new, high-resolution correlation panel to demonstrate the existence of a new lacustrine sequence stratigraphic concept: the Supply-Generated Sequence (SGS), which allows subdivision of the cyclically deposited alluvial, fluvial, and lacustrine facies in the Sunnyside Interval based on identifiable stratigraphic horizons, indicating periods of marked clastic input followed by subaqueous lake deposition. This novel conceptual framework helps address the inadequacy of previous sequence stratigraphic interpretations of the Sunnyside Interval. Conventional interpretations rely on premises regarding base level and sediment discharge that were developed for marine settings and do not apply directly to lacustrine systems because the creation and preservation of sedimentary deposits must logically occur during base-level rise in lake basins. In marine settings, base-level draw-downs are interpreted as the common causal mechanism for deltaic progradation, leaving sediment supply as a secondary consideration. In lacustrine systems, accommodation and sediment-supply are generated by water and sediment discharge routed through tributary rivers, making pulses of deposition inherently transgressive in nature. Our findings corroborate recent studies that consider the large, channelized sandstone deposits (shown to be accompanied by δ13C negative excursions) of the Sunnyside Interval to be discharge macroforms deposited during orbitally forced high-discharge early Eocene Hyperthermal events that lasted ~40 kyr. We also document the lateral complexity and discontinuity of hyperthermal sandstone event deposits and show the approximate durations of Sunnyside Interval SGSs to be 40-50 kyr, adding further evidence for the hyperthermal forcing mechanism model. We examine four previously proposed analogs of the Sunnyside Interval System, comparing basin type, morphology, lake level change, and depositional slope. We submit that the Neales River Delta in Lake Eyre, Australia is the best modern analog for the Sunnyside Interval System is due to its morphological and stratigraphic similarities. Ultimately, we characterize the Sunnyside Interval System as a “Supply-Controlled Splay-Delta” with high sediment and water supply during transitory hyperthermal events and low sediment and water supply during inter-hyperthermal periods. The depositional system acted as both a terminal splay or a fluvially dominated delta guided by the interplay of supply and accommodation in Eocene Lake Uinta.

Red siliciclastics and evaporites of Permian Nippewalla Group in mid-continental US were deposited in western equatorial Pangea. Previous studies of these rocks record Permian air temperatures as high as 73 °C, saline lake waters with a pH as low as ~1, and sedimentology that shows arid conditions. This current study conducts detailed sedimentological observations and geochemical analyses of the Blaine Formation of the Nippewalla Group. The Rebecca K. Bounds core from west-central Kansas is used to interpret the depositional environments and diagenetic history of the Blaine Formation. The lithologies of the Blaine Formation, listed in order of most to least abundant, are displacive halite, bedded gypsum/anhydrite, bedded halite, siliciclastic mudstone, and crystalline carbonate. These units represent a neutral-to-acid, perennial-to-ephemeral, saline lake-mudflat-desert soil system. The displacive halite lithology, consisting of randomly orientated halite crystals in a red mudstone matrix, represents a mudflat environment with shallow saline groundwater. The bedded gypsum/anhydrite lithology has three major textures: bottom-growth, laminated, and massive textures. The bottom-growth and laminated gypsum/anhydrite formed by chemical precipitation in a shallow saline water environment. The massive gypsum/anhydrite texture was possibly deposited as physically reworked grains. Bedded halite has cumulate and chevron crystals, dissolution pipes, and efflorescent crusts. These features indicate that evapoconcentration, flooding, and desiccation events occurred in a shallow ephemeral saline lake environment. Additionally, the iron-oxides, presence of “hairy blobs”, and the paucity of carbonates in the bedded halite shows that these were likely acid saline lakes. The siliciclastic mudstones are massive, red, and represent dry mudflats which experienced infrequent flooding and displays pedogenic overprinting. The thin crystalline carbonate unit is composed of diagenetic dolomite and halite. Original deposition may have been as detrital grains or as a chemical sediment that underwent diagenesis. The Blaine Formation has a complicated diagenetic history. Many of the early diagenetic features are related to dissolution, desiccation, and pedogenesis. Later diagenetic processes formed pseudomorphs, cements including magnesite, dolomitic interlocking crystal mosaic, and quartz veins and overgrowths. Dehydration and rehydration of gypsum and anhydrite plausibly occurred throughout the paragenetic sequence. Detailed sedimentology of the Blaine Formation marks an arid time consistent with the other formations of the Nippewalla Group. Similarities with Permian and Triassic red beds and evaporites from other well-preserved cores reveal that these acid saline lake systems were widespread across much of Pangea.

In this dissertation, I document three multifaceted investigations in which I tested hypotheses regarding the formation of crater-interior features on Mars. The first investigation was global in scope. In it, I tested groups of previously proposed formation mechanisms for central pits – centrally located depressions within certain complex craters – based on observed morphologies that would be expected for each. These groups of mechanisms are (A) explosive volatile release, (B) central peak collapse, and (C) drainage of subsurface melted volatiles. The results of inferential statistical tests do not point to any single group of mechanisms as causative of central pits, although they do support some component of central peak collapse in central pit formation. The results of this study suggest that central pit formation may require some combination between these formation mechanisms and/or other untested process(es). I next tested the hypothesis that central pits hosted paleolakes. This testing was accomplished by inspecting 96 central pit craters with valleys leading to their central pits, previously identified through a global inspection of CTX images. I used a suite of analyses to identify which central pits had the most evidence in support of a paleolake. Such evidence could include (1) outlet channels, (2) polygonal ground suggestive of desiccation cracks, (3) slope characteristics of valley terminal deposits consistent with deltas, (4) grain sizes and grain size spatial distributions consistent with deltas, and (5) spectral signatures of evaporites or hydrated materials. I found two central pits with two lines of evidence and three central pits with one line of evidence in support of such a paleolake. This number of craters is likely a minimum value due to incomplete data coverage and obscuring erosion and mantling deposits, suggesting that >5% of central pit craters globally had lakes. Finally, I tested the hypothesis that five craters within the Aeolis Dorsa region, which exhibits extensive paleofluvial and aeolian deposits, once hosted paleolakes. To test this hypothesis, I mapped, characterized, and interpreted intracrater sedimentary deposits. I present possible unit origins and discuss similarities with deposits exterior to the craters. Inferred depositional origins include aeolian, fluvial and (potentially) lacustrine environments.

The object of this thesis is a modestly scaled house at Smith Mountain Lake. The objective of this thesis is to please the senses through material composition. We gain knowledge and sensible understanding of our world through physical interaction and direct sensory experience. Through touching, smelling, listening, and observing we form and guide our choices. These experiences enrich the designer's knowledge of material properties and thus the proper use of materials. The primary focus of this study seeks to understand the physical properties of materials in relation to a site and to each other. Following, it attempts to transform these materials into elements of architecture, as the functional components of a building. Forms derive their unique qualities from these materials; qualities that enrich our consciousness, evoke sensible memories, and fulfill expectations. Chosen for their qualities as well as their perceptions, brick and wood, present a dynamic dialogue about mass in volume.The story of this house is told in relation to how the brick responds to the primary structure and how it orchestrates architectural elements within the whole. The dichotomy between these two materials lends this study to a larger exploration of joinery. The internal joining of wood to wood, or tectonic joining, produces a different expression than the joining of different materials. Wood to brick, for instance produces the legible differentiation of the architectural elements within the house. The arrangement of these materials articulates structure as well as spatial distinctions within the whole. Where volumes detach, glass bridges these materials as its attributes blend the differentiation between an interior and exterior condition. Articulating how these materials meet addresses essential architectural questions of knowledge, thought, and order as well as ephemeral pleasures. To enjoy the physical experience, as it is embraced by all of the senses, is the final goal and desire of this thesis.

The water's shore, used for defense, trade, transportation and industry, always plays an important role in a city's development. Buildings were built there to fulfill related practical functions, such as barns, factories or piers. However, at the present time, the functions mentioned above are not the only purpose of the shore, now more entertainment activies happen along the water's edge. Therefore, architecture's roles are changing. The site is in a small town called Riva San Vitale, which is located at the south end of Lake Lugano, Switzerland. For this small town, lake's shore is usually used by local people as a place for relaxation. Based on my four-month long living experiences there, I decided to design an art center on the lake to enrich residents' daily life.

Chapter 1: Lake Vostok is named for the nearby Vostok Station located at 78°28’S, 106°48’E and at an elevation of 3,488 m. The lake is covered by a glacier that is approximately 4 km thick and comprised of 4 different types of ice: meteoric, basal, type 1 accretion ice, and type 2 accretion ice. Six samples were derived from the glacial, basal, and accretion ice of the 5G ice core (depths of 2,149 m; 3,501 m; 3,520 m; 3,540 m; 3,569 m; and 3,585 m) and prepared through several processes. The RNA and DNA were extracted from ultracentrifugally concentrated meltwater samples. From the extracted RNA, cDNA was synthesized so the samples could be further manipulated. Both the cDNA and the DNA were amplified through polymerase chain reaction. Ion Torrent primers were attached to the DNA and cDNA and then prepared to be sequenced. Following sequencing the sequences were analyzed using BLAST. Python and Biopython were then used to collect more data and organize the data for manual curation and analysis. Chapter 2: As a result of the glacier and its geographic location, Lake Vostok is an extreme and unique environment that is often compared to Jupiter’s ice-covered moon, Europa. Lake Vostok was originally thought to be sterile, but multiple studies have suggested that not only is there a variety of bacterial and eukaryotic organisms living in the lake, but it may contain a complex ecosystem. The results of this analysis yielded metagenomic and metatranscriptomic data that aligned with a wide variety of organisms from 30 different phyla. The associated organisms were capable of many metabolic pathways, such as the nitrogen cycle and carbon fixation, as well as oxidation and/or reduction pathways for sulfur, iron, arsenic, hydrogen, hydrocarbon, phosphorous, uranium, and chromium compounds. The number of organisms unique to each sample was quite high for all samples except the layered meteoric ice sample, which only contained sequences similar to one organism. These results, combined with previous research, indicates that Lake Vostok is a transitory repository of DNA and organisms from the glacier, and also contains a much larger dynamic community and ecosystem.

Abstract: The preservation of biodiversity on our planet is crucial to our health. However, we cannot preserve what we do not understand. Biodiversity surveys most often forget to include some of the most diverse organisms on our planet, the parasites. Historically given a bad rap because of the diseases they can cause, parasites are often not thought of as organisms we should preserve. What most do not realize is that parasites are engrained in food-webs and ecosystems, playing many different important roles in the processes that regulate populations and more. Parasites can also form their own communities, and the processes that underly their assembly can have important impacts on the transmission of certain diseases. The focus of my doctoral research has been to examine the diversity and assembly processes of digenean trematode communities in Alberta, and the implications of community dynamics on their transmission of in recreational lakes. Trematodes are parasitic flatworms that have complex life cycles involving two or more host species. Some of the underlying factors that can affect trematode community assembly in their snail hosts are environmental factors that relate to the quality of the ecosystem, and therefore the suitability for their hosts. As well, the ecological interactions, those occurring between species, such as competition and predation, can impact community assembly as well. So, if we have an understanding of how trematode communities are formed, we may predict how changes to the important factors may impact the transmission of diseases they can cause. I conducted a longitudinal species survey of snails and trematodes across six lakes in central Alberta over three summers. From the survey, we applied morphological and molecular genetic analyses to identify snail and trematode species. Overall, we uncovered an incredible diversity of trematodes, with 67 species and counting. Surprisingly, there were only five snail species needed to host them. From spatio-temporal analyses, we found no clear patterns for species composition in communities, though it does appear as if the ecoregion and the amount of nutrients in the water determining the trophic status may be playing a role. Furthermore, for some very abundant species, dissolved oxygen content in the water is an important predictor for their presence. All communities examined shared a trematode composition pattern of a few highly abundant and common trematode species, and many rare and inconsistent species. This information has important implications for the local public health issue of swimmer’s itch in Alberta. Swimmer’s itch is a re-emerging, neglected allergic condition caused by trematodes of the family Schistosomatidae. People are exposed to the larvae of schistosomes when swimming and recreating in natural water bodies. The larvae emerge from their snail first intermediate host and actively penetrate the skin of unsuspecting swimmers, causing a rash that can last up to two weeks. What these larvae are actually attempting to do is to infect a duck, their definitive host. These accidental exposures to humans have many downstream public health impacts, most being indirect effects as a result of discontinued use of lakes for recreation, due to the economic, cultural, and spiritual values associated with them. My doctoral research has laid the foundation for understanding the aspects of the swimmer’s itch issue, the biological side and the human perspective. From our species survey, we found seven schistosome species capable of causing swimmer’s itch, and all were rare in each community. This was a surprising result, given that our swimmer’s itch survey, a longitudinal survey of people who had experienced swimmer’s itch from across Canada, revealed many reports of swimmer’s itch every year, even from the lakes we had directly sampled snails from. In total, in Alberta there were 101 lakes that had reported swimmer’s itch over five years. One trend found among both surveys was the occurrence of peaks in trematode species diversity, snail infection prevalence, and swimmer’s itch occurrences during the months of July and August, which will be an interesting avenue for future research. Overall, my doctoral research has contributed to a broad understanding of swimmer’s itch transmission, as well as the spatio-temporal dynamics of trematode community assembly processes.

The Last Glacial Maximum (LGM; ~23,000-19,000 years ago) and subsequent deglaciation (~19,000-11,000 years ago) represents the last major global climatological transition. In the Western United States, the LGM and deglacial were both characterized by increased effective moisture and expansive lake systems, with most lake growth and maximum lake extents achieved during the deglacial period. In stark contrast, the modern Great Basin is characterized by aridity and low effective moisture. The factors contributing to these large-scale changes in hydroclimates are critical to resolve, given this region is poised to undergo future anthropogenic-forced climate changes with large uncertainties in model simulations for the 21st century. Furthermore, there are ambiguous constraints on the magnitude and even the sign of changes in key hydroclimate variables between the LGM and present-day in both proxy reconstructions and climate model analyses of the Western United States. In this work, I present new stable and clumped isotope data from several ancient lakes, analyze this new data in concert with previously published data, and compare both new and existing results to climate model simulations. Radiocarbon dated samples from ancient lakes constrain lake elevation and the timing of lake level fluctuations. Using a hydrological modeling framework, clumped isotope data constrain several other hydroclimate variables including temperature, precipitation rate, and evaporation rate, which are all used to assess climate model simulations of the same hydrological variables. In Chapter 1, I compile new and existing radiocarbon ages from post-LGM lake basins, and provide an analysis of changing effective moisture through time and space. In Chapter 2, I provide a detailed analysis of our data from one specific basin, Lake Surprise, and provide evidence of evaporation depression as a key driver of lake growth. Finally, in Chapter 3, I use clumped and stable isotope analysis of samples collected across the Great Basin (by UCLA students and others) to provide evidence for spatial and temporal variation in hydroclimate. Concomitant analysis of proxy data and climate model simulations provides a robust means to understand past climate change, and by extension, predict how current hydroclimates may respond to expected future climate forcings.

Abstract: Climate change across northern latitudes is fundamentally altering the hydrological cycle there, resulting in increased glacial melt, permafrost thaw and precipitation. Whereas enhanced glacial melt has potentially important implications for water quality and productivity in downstream freshwater ecosystems, little is yet known about how glacial meltwaters impact biogeochemical cycles of both nutrients and contaminants across glacierized watersheds, a critical gap in our ability to predict the future quality of freshwater resources in the North. To address this, we integrated principles from glaciology and limnology in a multi-year (2013-2017) study of freshwater quality and productivity across the glacierized High Arctic Lake Hazen watershed on northern Ellesmere Island in Nunavut Canada, from glacier termini through rivers and lakes to the nearshore marine environment. We first examined nutrient (nitrogen, phosphorus, iron, silica) and carbon retention and mobilization across the glacierized land-to-ocean aquatic continuum (Chapter 2). Largely particle-bound nutrients (total phosphorus, iron, nitrogen) from the glacier-fed rivers were deposited to the depths of the lake by turbidity currents generated by the glacial inflows. Lake Hazen was also a sink for dissolved nitrogen species and dissolved organic carbon, likely due to biological processes, but a source of dissolved inorganic carbon (DIC) to the Ruggles River outflow. To understand this source of DIC, we then focused on DIC and by extension, dissolved carbon dioxide (CO2) concentrations across the watershed (Chapter 3). At the watershed scale, the glacier-fed rivers were a strong, previously overlooked sink of atmospheric CO2 due to the strength of CO2-consuming chemical weathering reactions involving the large loads of comminuted sediments entrained by glacial meltwaters as they traveled across the poorly consolidated proglacial zone. As the reactions consumed CO2, they also generated DIC, resulting in the net export of DIC from Lake Hazen to the Ruggles River. These reactions intensified with increasing discharge and distance from the glaciers and continued into the lake, resulting in CO2 undersaturation even at 267 m depth. Finally, we used a mass balance approach to identify sources and sinks of neurotoxic methylmercury (MeHg) and total mercury (THg) across the watershed (Chapter 4). Glacial meltwaters were annually the most important source of THg to Lake Hazen and MeHg. Because much of this mercury was particle-bound and deposited to the bottom of the lake, Lake Hazen was a large sink for both MeHg and THg, resulting in low MeHg and THg exports to the Ruggles River. However, permafrost slumping and erosion along the banks of the Ruggles River significantly increased exports of MeHg and THg to coastal marine waters. This study highlights the importance of climate change-accelerated glacial melt to the biogeochemistry of downstream aquatic ecosystems.

Lakes continuously accumulate sediment, a process that has been ongoing since their formation. The sediment consists of soil particles and biological remains that runoff from the watershed and into the lake. The sediment may also contain particles from aeolian transported material from the “airshed” and biological and inorganic precipitated minerals. Thus, lake sediment is a continuous environmental archive, containing information about the history of the lake, and its surroundings. Unfortunately, lake sediment is subject to remobilization and mixing due to a variety of sediment transport processes, such as mass wasting. There has been limited research on how base-level change influences mass wasting, in particular, slope failure. Some studies suggest slope failures are correlated with base-level fall and/or base-level rise, while others suggest they don’t correlate at all. To address this controversy, I conducted flume experiments at the Saint Anthony Falls Laboratory (SAFL) to observe slope failure in sediment mixtures containing four different walnut-shell/kaolinite ratios. Three base-level change rates were tested, producing 12 base-level change experiments. Another set of experiments was also designed to investigate what effect, if any, the addition of waves would have on mass flow. Video recordings were taken during each experiment and were analyzed to study the geometry of each profile before and after base-level change had occurred. Results suggest that there is consistent sediment transport when waves are present, aiding in the transportation of walnut-shell downslope. Without waves, transport is limited, and the clinoform is subject to compaction, or slump formation, depending on clay content. This difference depends heavily on a sediment’s composition, where hydraulic conductivity (K) plays an important role in water transmission through the clinoform. My experiments suggest that slope failures in the field would occur in lake sediment with higher clay content. Base-level change itself has no effect on the occurrence of failures, but slope failures should occur during base-level change if clay content is high. With only base-level change, we can expect to see compacted lake sediment with lower clay content (~15-33% clay). Slope failures (slumps) occur in lake sediment with higher clay content (~50%). With the presence of waves, however, wavebase plays an important role in sediment transport. Wave-base greatly influences sediment transport downslope, which is seen in my experimental work. This suggests that waves in the field also transport lake sediment downslope while washing away any finegrained particles (i.e. clay).

Anthropogenic contributions of mercury (Hg) and other contaminant metals to northeast Ohio likely derive from a variety of sources including coal combustion, waste incineration, and landfills. This Hg is transported through the environment and can accumulate in the bottom sediments of rivers and lakes. For this study, Hg concentrations were measured in soil, surface lake sediment, and sediment cores from Summit Lake, which is situated within the urban core of Akron, Ohio and Rex Lake, which is located 8 km to the south in a suburban setting. These two lakes were sampled because of their contrasting locations to potential Hg point sources. Around Summit Lake, soil samples collected in 2016 have Hg concentrations that range from 0.06 ± 0.01 µg/g to 0.85 ± 0.01 µg/g. Surface sediment was collected from Summit Lake in 2001 and 2015. For samples collected in 2001, Hg concentrations in organic rich mud range from 0.23 ± 0.01 µg/g to 1.05 ± 0.02 µg/g and in samples from 2015, values range from 0.10 ± 0.01 µg/g to 0.58 ± 0.02 µg/g. Locations having elevated Hg concentrations in soil and lake surface sediment within Summit Lake are associated with a land-fill in the southeast area of the lake. A sediment core collected from Summit Lake displays a record of change from pre-industrial (depth below 308 cm) through industrial, to post-industrial (depth above 97 cm). The change in the surrounding land is reflected in the change in the organic carbon concentration and C:N ratios. During the pre-industrial period ratios average 11 ± 1 (n = 8), and then during industrialization C:N ratios significantly (p < 0.05) increase to 33 ± 1, with the industrialization period having an average C:N ratio of 20 ± 7 (n = 55). During industrialization organic carbon decreases with an increase in Hg and other contaminant metals (chromium, copper, lead, mercury, and zinc) concentrations. These additional metals were analyzed on many of the same materials as the Hg concentrations and were presented previously (Haney, 2004; Mitchell, 2014). Chromium, copper, and lead begin to increase at a depth of 280 cm and remain elevated throughout the industrial period, until a depth of 97 cm, when contaminant metal concentrations decrease. The first contaminant metal to peak in the sediment core was mercury (10.9 µg/g) at a depth of 236 cm, with zinc (8010 µg/g) concentrations peaking at 235 cm. C:N ratios for post-industrialization period average 15 ± 3 (n = 39) with uniform delivery of organic carbon from 0 to 39 cm (9.2 ± 1.1%, n = 39). Rex Lake, 8 km south of Summit Lake, is surrounded by suburban land uses and forests. Soil samples collected around Rex Lake in 2016 have Hg concentrations that range from 0.03 ± 0.01 µg/g to 0.13 ± 0.01 µg/g and uniform C:N ratios 16 ± 2. Surface sediment samples collected from Rex Lake in 2014 range from 0.05 ± 0.01 µg/g to 0.79 ± 0.02 µg/g. Two lake surface samples from Rex Lake have significantly (p < 0.05) higher Hg concentrations than other samples collected, and were collected in the north central area of Rex Lake. Organic rich mud samples from Rex Lake have a uniform distribution of organic matter with C:N ratios averaging 12 ± 2 (n = 8). The sediment core collected from Rex Lake also shows a steady increase in organic carbon and contaminant metals beginning at a depth of 63 cm. Prior work showed that chromium, copper, lead, and zinc all begin to increase during the start of industrialization, and then decrease at the start of post-industrialization, around a depth of 30 cm. Similarly, our study suggests that although anthropogenic activities continue to contribute to soil and lake sediment Hg concentrations, these contributions have been decreasing since the enforcement of the Clean Air Act in 1970. Hg variations between and within the systems are likely impacted by both previous or “legacy” anthropogenic activities as well as ongoing activities. Urban Summit Lake has significantly higher Hg concentrations compared to suburban Rex Lake for soil, surface sediments, and within the sediment core. Despite these elevated contaminant metal concentrations, there appears to be an overall declining trend in contaminant metal concentrations consistent with the broader decline since the peak concentrations observed in the sediment cores.

To provide greater spatial coverage of late Pleistocene to Holocene environmental change in the Midwestern United States, a 1350 cm long sediment core was collected from Silver Lake in northeast Ohio. Age control was provided by new radiocarbon dates, correlation to a dated lake record from western Ohio, and a prior study of Silver Lake. Lithologic descriptions and sedimentary profiles of dry bulk density (DBD), organic matter (OM), carbonate, C/N, grain size, magnetic properties, and concentrations of terrigenous derived elements (Al, Ti, and K) allow the core to be divided into six periods. The climate interpretations are compared to published regional and hemispheric climate records. The first period is Deglaciation, which spans from 17,560 – 13,600 cal year BP (1353 - 1188 centimeters below lake floor (cmblf)). Silty sediment with low OM (average 6 %) and high DBD (average 0.832 g/cm3) are interpreted to reflect cold conditions soon after deglaciation. The Latest Pleistocene Period is the second period and spans from 13,600 – 12,200 cal yr BP (1188 – 1103 cmblf). Brown to light brown mud with silty layers, a slight increase in % OM (average 9 %) and decrease in DBD (average 0.694 g/cm3) characterize this interval. The Latest Pleistocene Period may have been a time of increased primary productivity in Silver Lake. The third period is the Younger Dryas, which spans from 12,200 – 11,500 cal yr BP (1103 – 1070 cmblf). Gray-brown to light-brown silty mud having low % OM (average 6%), high DBD (average 0.703 g/cm3), high concentrations of magnetic minerals, and elevated concentrations of Al, Ti, and K characterize this period. These sediment characteristics are interpreted as cold and dry conditions, increased terrigenous input, and/or decreased primary productivity. The fourth period is the Early Holocene which spans from 11,500 – 7,450 cal yr BP (1070 – 824 cmblf), and is divided into two subperiods. During the first subperiod, from 11,500 – 10,600 cal yr BP (1070 – 1016 cmblf), there was an increase in % OM (average 28 %) and decrease in DBD (average 0.311 g/cm3) and concentrations of Al, Ti, and K. The first subperiod of the Early Holocene is interpreted to be a period of brief warming. The second subperiod of the Early Holocene spans from 10,600 – 7,450 cal yr BP (1016-824 cmblf), and is characterized by highly variable % OM and DBD and increased Al, Ti, and K. This subperiod is interpreted as a period of increased aridity. The fifth period is the Mid to Late Holocene which spans from 7,450 – 200 cal yr BP (824 – 128 cmblf). Alternating brown and dark brown mud having no visible silty layers, high % OM (average 51%), low DBD (average 0.116 g/cm3), and decreased Al, Ti, and K and magnetic concentration characterize this period. These sediment characteristics are interpreted to reflect warm and moist conditions when primary productivity increased and/or terrigenous influx decreased. However, within the Mid to Late Holocene Period there are six pronounced intervals of decreased % OM and increased Al, Ti, and K suggestive of millennial-scale increases in terrigenous input and/or decreases in lake productivity. These six intervals may be related in part to rapid global climate changes during the Holocene, when temperatures and moisture balance fluctuated. The sixth period is the Anthropogenic Period, which spans from 200 cal yr BP to the present (128 – 0 cmblf). The Anthropogenic Period is characterized by a pronounced decrease in % OM (average 19%), increase in DBD (average 0.273 g/cm3), and an increase in the mass accumulation rate (MAR) resulting from Euro-American land clearance enhancing watershed erosion.

Sediment core archives provide a history of data useful for serving as a long-term monitoring reserve to evaluate chronological events of contamination to lake systems. This could be an effective tool for continual environmental management, monitoring and potential restoration efforts. This method is also very cost-effective without the addition of a water quality monitoring station on site. Taking 3 sediment cores from Punderson Lake Ohio for analysis has allowed associating variations in select metals to anthropogenic events or activities; we can determine a time frame with limited uncertainty and resolve the intensity of anthropogenic contamination to the lake starting with post World War II contamination till the present. We used sedimentation rate in conjunction with radiometric dating methods of 137Cs to establish a timeline through the cores. Applying mass depth g/cm2 (Matisoff and Whiting, 2011) and core segmentation intervals (1cm) we can remove issue of porosity and compaction. Selected trace elements (As, Cu, Mn and Pb) were studied in these sediment cores. We can parse natural crustal sources of sediment input from anthropogenic sources using a method known as enrichment factor (EF) (Feng et al., 2004). This method requires the normalization of trace metal concentration against Al into an index/dimensionless data form (Essien et al. 2009). EF index implies a severity of contamination in a sediment interval allowing for the consideration of environmental impact, status of pollution and possibly source the contamination of the select trace metal. We can then plot EF over time to obtain relative burial times of the excess trace metals. We can then make a comparison to other regional lakes to see how anthropogenic source contamination appears in other systems. We used diatoms as a biological component as they are sensitive to ecosystem/environmental changes and preserve well in buried sediment. Therefore; diatoms can be seen as responding to possible human influences that are changing the habitat or quality of the lake. We found correlations within the core showing trace element pollution related to anthropogenic activities. Primarily we can see strong signals of Pb and As in earlier portions of the core indicative of industrialization and fossil fuel burning of the time. We also see a rise in Cu enrichment at the top of the core which, is linked to CuSO4 additions to the lake. Diatoms confirm that the CuSO4 is having an impact on biotic components of the lake particularly changing their community structures. It is important to consider the benefits of this type of study. Future benefits such as building and periodically updating a data base that can be used to track a lake systems contamination levels and provide invaluable insight into remediation and site maintenance efforts.

At the beginnings of this thesis, the importance was solely focused on the design of an independent multipurpose theater and the transitions between the public area and backstage. As the year and project progressed, it changed to become a realization and study of architectural experiences within a space. After choosing a site within the Snoqualmie National Forest in Seattle overlooking Lake Serene, decisions were made to design a theater that would not hinder the natural landscape but immerse the audience in it. Years of backpacking, camping, and hiking, I have personal experiences and memories of walking through the shafts of light shining through the canopies of the trees or feeling the dampness that sticks to clothes as you roam through the fog rolling off the mountains. The orientation and exterior choices were made as to not take away from an audience member's experience of the natural surroundings of the area. Blending the building within the mountain hides it from view as to not over take the landscape behind it, the bridge connects the two mountains to each other and the building itself creates an axis towards the lake. The movement through the lobby was designed as a natural progression towards the view as a canopy of timber surrounds the audience, mimicking the trees outside. How we perceive architecture is how we experience it. Creating a space that would not only flow with its natural environment but also have movement inside to assist each individual, whether it is a visitor, stagehand, technician, or performer was my end goal. Focusing my efforts on the visitor, I was able to learn the importance of moments and the simplicity of details. Taking ultimately what Juahani Pallasmaa is quoted saying that "the architectural experience calls for the senses of balance, movement, orientation, continuity, time, self, and existence."

Understanding the transport processes in lakes and other aquatic systems is vitally important since much of the living biomass is transported by the water, along with nutrients, contaminants, suspended particles, and other materials important to biogeochemical processes. The hydrodynamic processes therefore determine the environmental conditions that affect the biogeochemistry. The physical processes that control the hydrodynamics of large lakes are complex, and depend on a balance of characteristics of the lake (geometry, stratification, etc.) and forcing conditions (meteorological, hydrological) that change over various spatial and temporal scales. Using data from several extensive field campaigns, including measurements of velocity and thermal structure at multiple locations over several seasons, an extensive set of CTD data, and a 15 year long bi-weekly water quality dataset at multiple locations, we analyze the physical forces controlling the dynamics of a large, narrow and deep lake, and the response of the lake to these forces. The study site is Cayuga Lake, the second largest of the Finger Lakes of central New York State, USA (latitude 43N). It is a long (60 km), narrow (less than 6 km) and deep (maximum 130 m) lake. The bathymetry at the south end of the lake slopes up to a shallow shelf, not unlike a coastal estuary, which receives discharges from both natural and anthropogenic sources, and on which sharp spatial and temporal gradients in water quality exist. The geometry of the lake and the prevailing winds in the region lead to the generation of large amplitude internal waves, which develop to be highly nonlinear. Shoaling of these waves on the southern shelf are shown to lead to the intermittent upwelling of hypolim- netic water on to the shelf, creating sharp spatial gradients in water quality (e.g., TP and chlorophyll-a concentrations) on the shelf. We analyze the internal wave field of the lake and the nonlinear processes associated with it, and the factors that lead to the sharp spatial gradients observed on the shelf. We show that a subtle balance of forces controls mixing and transport in the various regions of the lake and propose an explanation for a persistent anomaly in chlorophyll-a concentration observed in one region of the lake.

The western Sandhills of Nebraska contain many shallow lakes and wetlands that interact strongly with groundwater and the overlying atmosphere. The region is semi-arid, and most of the lakes are saline, supporting a wide range of ecosystems. Water levels and salt concentrations are highly sensitive to variations in precipitation, evaporation, and groundwater fluxes, making the Sandhills an excellent laboratory for examining the effects of climate on the water balance of interdunal lakes. In this study, we investigate the atmospheric controls on evaporation rates, as well as the water balance of Alkali Lake, one of the more saline lakes in the western Sandhills. The Bowen ratio energy balance and mass-transfer methods are applied over a three-year period (2007-2009) to quantify summer evaporation rates. Daily evaporation is found to vary widely, but averages around 5-6 mm/day during the summer. Evaporation rates are largely controlled by solar radiation on a seasonal basis and by variations in wind and vapor pressure gradient at shorter timescales. Adjustments for salinity affected the mass transfer method more than the energy budget method, with a root mean squared error of 0.49 mm/day, but only 0.09 mm/day for the energy budget method. Evaporation dominated the water balance during the summer months, exceeding precipitation by a factor of 3.2, on average. The lake water balance also indicates that evaporation exceeds the sum of all water inputs during summer months, causing lake levels to decrease in summer (but rebound during the winter). Net groundwater inflow is the largest source of water into the lake and averages 2.5 mm/day. Occasional negative net groundwater values indicate complex interactions between the coupled lake and groundwater systems. Lake reactions to precipitation inputs suggest that short term groundwater flow reversals are possible. Adviser: Diego Riveros-Iregui

Environmental fluctuations related to climate, biological productivity, and evaporation can be recorded by sedimentary archives within lacustrine depositional systems. Sediments within terminal, closed-basin lakes are amongst the most sensitive paleoenvironmental indicators, and have great potential for permitting detailed reconstruction of environmental conditions via a variety of geochemical and isotopic proxies. Microbialites, however, have been largely overlooked as repositories of paleoenvironmental data. Here, we investigate mineralized microbialites within Laguna Negra, a high-altitude (4100 meters above sea level) hypersaline, closed-basin lake in the Argentinian Puna region and explore the potential recovery of environmental signals from these unique sedimentary archives. Mineralized microbialites within Laguna Negra preserve complex layering composed of three distinct carbonate fabrics—isopachous cement phases, botryoidal precipitates, and microbially-associated micrite. These phases are interpreted to reflect differential physical and biological influences on carbonate nucleation and growth. Detailed preservation of successive laminae within these microbialites provides the opportunity for time-wise reconstruction of geochemical signatures. Geochemical analysis of Laguna Negra microbialites shows overall range of δ13[delta-13]Ccarb[carbonate carbon] is from +5.75‰ [permil] to +18.25‰ and from -2.04‰ to +7.36‰ for δ18[delta-18]Ocarb[carbonate oxygen]. Long-term signals preserved within successive laminae of lighter δ13Ccarb and δ18Ocarb through time suggests increased input water contribution since the beginning of microbialite deposition. General hydrological evolution of Laguna Negra is reconstructed via integration of observed oxygen isotopes signatures with published water balance models, and is consistent with regional records from other lacustrine systems. Examination of paired δ13Ccarb and δ13[delta-13]Corg[organic carbon] permits interpretation of the relative effects of evaporation and biotic activity in the evolution of Laguna Negra, and reveals that extrinsic parameters, such as CO2 [carbon dioxide] degassing and evaporation are the primary control on isotopic evolution. Geochemical and petrographic differences between microbialites across a spatial gradient, however, suggest that Laguna Negra microbialites also preserve signals that represent both heterogeneous evolution of environments within the lake and influence of biogenic activity. Ultimately, understanding of the relative effects of environmental and biotic parameters on the evolution of lacustrine deposits will enhance our understanding of both paleoenvironmental change and its potential relationship to microbialite mineralization.

In this dissertation, I have completed a research project that focused on reconstructing past climate and environmental conditions in the Great Basin of the western United States. This research project incorporates four discrete but interrelated studies. (1) The geochemistry of lake sediments was used to identify anthropogenic factors influencing aquatic ecosystems of sub-alpine lakes in the western United States during the past century. Sediment cores were recovered from six high elevation lakes in the central Great Basin of the United States. Mercury (Hg) flux varied among lakes but all exhibited increasing fluxes during the mid-20th century and declining fluxes during the late 20th century. Peak Spheroidal Carbonaceous Particles (SCP) flux for all lakes occurred at approximately 1970, after which SCP flux was greatly reduced. Atmospheric deposition is the primary source of Hg and anthropogenically produced SCPs to these pristine high elevation lakes during the late 20th century. (2) Chironomids are used to develop centennial length temperature reconstructions for six sub-alpine and alpine lakes in the central Great Basin of the United States. Chironomid-inferred temperature estimates indicate that four of the six lakes were characterized by above average air temperatures during the post-AD 1980 interval and below average temperatures during the early 20th century. This study adds to the growing body of evidence that sub-alpine and alpine lakes in the western United States have been, and are increasingly being affected by anthropogenic climate change in the early 21st century. (3) A sediment core representing the past two millennia was recovered from Stella Lake in the Snake Range of the central Great Basin in Nevada. The core was analyzed for sub-fossil chironomids and sediment organic content. The chironomid-based mean July air temperature (MJAT) reconstruction suggests that the Medieval Climate Anomaly (MCA), was characterized by MJAT elevated 1.0°C above the subsequent Little Ice Age (LIA), but likely not as warm as recent conditions. The Stella Lake record provides evidence that elevated summer temperature contributed to the increased aridity that characterized the western United States during the MCA. (4) Lake sediment cores spanning roughly the last 7,000 years were recovered from four small sub-alpine and alpine lakes located in central Great Basin of the United States. Reconstructions of MJAT were developed for each of the study sites using a chironomid-based inference model for MJAT (two-component Weighted Averaging-Partial Least Squares (WA-PLS)). The elevated temperature that characterizes the mid-Holocene at Stella Lake is surpassed only during the Medieval Climate Anomaly and in the post-AD 1800 interval. The reconstructions for the sites located in the northern portion of the study transect are characterized by greater variability, likely reflecting the influence of both radiative forcing and catchment-specific conditions.

Abstract: The potential for walleye (Sander vitreus) restoration at Lac la Biche, Alberta, Canada is a social-ecological question that requires understanding of changes to ecosystem integrity and historical fidelity resulting from disturbance. This study explored variability in fisheries-induced disturbance across time, examined the effects of disturbance on ecosystem structure and functioning, characterized the system during different eras from pre-European settlement to the present, and assessed walleye restoration potential based on conceptual models describing the system response to disturbance. An anthropological assessment of historical harvest was conducted (1800 to 1900) to estimate the magnitude of subsistence lake whitefish (Coregonus clupeaformis) harvest during rapid settlement of the Lac la Biche area. The results were compared to more recent harvest estimates (1900 to 2009) reflecting combined commercial, subsistence and recreational harvest, to describe the relative variability in the magnitude of fishing disturbances during the 200 years preceding the current restoration project. Ecosystem models for 1800 and 1900 were used to examine how historical fisheries affected the structure, functioning, and resilience of the system, and to assess if targeting system conditions in 1900 would satisfy the restoration goal of a walleye-dominated ecosystem. Results suggest little change in ecosystem structure and function between 1800 and 1900, though the trend in the analyses is towards declining system maturity and resilience. Parameters and state variables used as model inputs provide plausible values for guiding the restoration program. Potential success of the walleye restoration program was addressed using a series of models representing four eras (1800, 1900, 1965, 2005) to test the for multiple ecosystem states, specifically a walleye-dominated equilibrium and a double-crested cormorant (Phalacrocorax auritus) dominated equilibrium. Identification of alternate stable attractors would influence the predictability of system recovery following a disturbance. Results from over 900 model simulations suggest both walleye and cormorant attractors existed in historical (1800, 1900) models but a single cormorant-dominated equilibrium is present in contemporary models (1965, 2005). Differential size-selective foraging of walleye and cormorants on yellow perch (Perca flavescens) provides a negative feedback stabilizing each state. Recovery of a walleye population seems possible but restoration of a walleye-dominated ecosystem was not predicted.

Aquatic plants (macrophytes) are an undervalued but critically important component of Minnesota's lakes. The macrophyte Index of Biotic Integrity (IBI) was developed to evaluate lake health using metrics that describe the condition of the aquatic plants. However, a detailed evaluation to determine whether the index can explicitly link lake condition with activities that negatively impact lake resources has not been conducted. This information is necessary before the IBI can be used to develop biological standards required under the federal Clean Water Act. The goal of this dissertation was to develop and implement a framework for identifying the strengths and weaknesses of the index to inform biological assessment. Four chapters describe research to fulfill this goal. The first chapter identifies comparable groups of lakes using a set of environmental variables that influence macrophyte community composition. The second chapter describes the development and application of semi-automated techniques for quantifying potential stressors of aquatic macrophytes in nearshore areas of lakes, such as docks and boat lifts. The third chapter provides a complementary analysis to chapter two by examining the relationships of shoreline development at different spatial scales with metrics describing macrophyte richness. The fourth and final chapter develops modeling techniques to quantify the relative effects of multiple stressors on the IBI. Specifically, I have used artificial neural network models that can 'learn' inherent data structures and are especially useful for modeling noisy data with non-linear relationships. Outcomes from my dissertation will inform management agencies on the most appropriate use of the index, which will ultimately facilitate the protection and restoration of Minnesota's lakes.

The Eocene Green River Formation (USA) contains one of the best known Konservat Lagerstätte in the fossil record. Whereas there have been many studies performed on the vertebrate fauna, particularly the fish, there have been relatively few studies done on the invertebrate fauna such as the ostracodes from this famous fossil deposit. Two species (Candona pagei and Hemicyprinotis watsonensis) were recovered from 16 intervals and three study sites from Fossil Basin, a sub-basin of the Greater Green River Basin. The two species represent differing ecological tolerances, both mud-dwelling and plant-dwelling. This formed the basis for a reconstruction of lake levels throughout the history of Fossil Lake. This in turn can be used to examine biotic response to climate change during the Paleocene-Eocene Thermal Maximum (PETM).Stratigraphic sections were measured at three sites and sampled for ostracodes. A 1 cm x 1 cm grid was used to quantify the number of ostracode valves in each sample. Lamination counts were also performed on samples collected in Smith Hollow Quarry (SHQ), which yielded the number of laminations per millimeter. This was compared throughout the section to assess how it changed throughout Fossil Lake's history at SHQ. Taphonomic uniformity was quantified by comparing the number of whole valves in the samples of kerogen-poor versus kerogen-rich laminated micrites (kerogen-rich micrites are thought to have been deposited under deep, anoxic water conditions), and then compared to each other. Frequencies of occurrence and abundances of individuals per bed were also compared between the two types of micrites. The trophic structure of the lake was also assembled to attempt a better understanding of the community ecology of Fossil Lake.This study demonstrates the utility of ostracode species assemblages in tracking lake-level fluctuations throughout the history of Fossil Lake during a time of climate change. This has important implications and applications for studies of current climate change.

Abstract: The mechanisms that contribute to the frequent switching of primary producer communities in shallow lakes on the Boreal Plains of Alberta, Canada were explored. The lakes tend to be clear and macrophyte-rich (61% of lakes) or turbid and phytoplankton-rich (30% of lakes). The study is based on surveys of twenty-three lakes on the Boreal Plains, Alberta, Canada monitored from 2001 to 2007. I examined the effect of annual fluctuations in precipitation on the limnological conditions of the study lakes and the primary producer communities. Drought concentrated nutrients, phytoplankton biomass and turbidity, decreasing macrophytes cover and promoting a phytoplankton-rich regime. Macrophyte abundance was better predicted by lake depth. During the study SAV cover increased with lake depth and was significantly higher in 2007 following three years of high water levels. Precipitation-induced switches occur because the lakes are small, isolated and the water budget is dominated by precipitation inputs and evaporative outputs with little surface or groundwater fluxes. The lake and landscape factors affecting the persistence of the macrophyte-rich regime and phytoplankton-rich regime were assessed. The macrophyte-rich regime was more persistent in shallow lakes (max. depth < 112 cm) with high macroinvertebrate predator biomass (> 580 µg L-1) and low TP concentration (< 58 µg L-1) (variance explained = 0.66). Lakes with high Daphnia dominance (> 61% of the Cladocera community) and higher TP concentration (> 67 µg L-1) were associated with a more persistent phytoplankton-rich regime (variance explained = 0.50). I examined the importance of food web structure in maintaining the alternative regimes. Food web structure appears important in maintaining the resilience of the macrophyte-rich regime in fishless lakes on the Boreal Plains. The macrophyte-rich regime is reinforced (stabilized) by top-down control of phytoplankton and periphyton by macroinvertebrates and zooplankton. In contrast, food web effects appear weak or absent in the phytoplankton-rich regime.

Abstract: Decades of fish introductions into mountain lakes have altered invertebrate communities. I assessed the current status of fish populations and their effects on crustacean zooplankton communities by sampling 37 lakes in the mountain parks, where stocking practices had been halted over 25 years ago. I discovered that introduced fish were more likely to persist in colder alpine lakes than in montane sites. However, their effects on total zooplankton biomass and species diversity increased with rising lake temperatures. Persistence of introduced fish in warmer lakes favored small-bodied zooplankton species, whereas larger-bodied communities in colder, larger alpine lakes were relatively unaffected. Greater resistance and resilience (i.e. recovery rate) of alpine zooplankton (e.g. Hesperodiaptomus arcticus) in deeper, fish-stocked lakes was likely attributable to a greater availability of refuge from predators and more abundant diapausing egg banks. Fish residence time and the species of stocked fish were key factors of taxonomic stability in perturbed zooplankton communities.

Winter surveys across Lake Erie between 2007 to 2011 documented diatom assemblages associated with extensive ice cover. This study aims to characterize these winter assemblages in terms of their community structure, their interactions, adaptations to a psychrophylic lifestyle and their role in the biogeochemistry of the lake. The winter assemblage was dominated by diatoms, specifically by Aulacoseira islandica (O. Müller) Simonsen (≈80%) and Stephanodiscus binderanus (Kützing) Krieger (≈19%), with other taxa like Fragilaria spp., Cyclotella spp., Asterionella spp., and Tabellaria spp. making up less than 1% of the assemblage. The detailed morphology of the two dominant taxa observed are described in this study, and the presence of resting cells and auxospores in filaments of A. islandica, but not in the other taxa are documented. The study compares different sample processing techniques for scanning electron microscopy (SEM), and describes a rapid and effective technique, substituting critical point drying (CPD) with hexa-methyl-di-silazane (HMDS) treatment, that allows viewing of fine details including the epiphytic colonization of the diatoms by flagellated rod-shaped bacteria embedded in an extracellular matrix. The study also describes ice nucleating activity associated with assemblages of filamentous diatoms sampled during winter and early spring across the Laurentian Great Lakes. The ability to promote ice formation offers a previously undescribed mechanism by which non-motile phytoplankton can attach to overlying ice and, thereby, maintain a favorable position in the photic zone. The ice nucleating activity is attributed to bacteria. Bacteria isolated from the phytoplankton showed high temperatures of crystallization (Tc) to -3°C. Ice-nucleating active (INA) isolates were identified as belonging to the genus Pseudomonas. Whereas INA bacteria have been isolated from lakes and streams, their presence in these environments is attributed primarily to runoff and atmospheric deposition as rain or snow consistent with their proposed role as biological ice nuclei in clouds. Far from a passive existence in the aquatic milieu, the INA microbes associated with winter diatoms in the Great Lakes may possess a role in promoting the formation of ice during winter and in so doing, promote the growth of their diatom hosts under ice. The novel mechanism presented may be relevant to temperate and polar ecosystems beyond the Great Lakes including coastal oceans. Finally, photosynthetic O2 evolution rates measured in winter support characterization of the assemblage as a photosynthetically robust population, with rates of primary production in winter higher than those measured in spring and comparable to those reported in summer. Results further suggest that the winter diatom assemblage may play an important role in the export of carbon to the benthos, thereby potentially driving the hypolimnetic oxygen deficits observed months later in summer.

The volume of methane (CH4) and other gases in sediments and the rate of CH4 ebullition were determined for a shallow eutrophic freshwater lake in Southern California. Gas volume, principally as CH4, was measured at 28 sites in July 2010, followed by monthly sampling at 7 sites through December 2011. Gas volumes measured in July 2010 at the 28 sites exhibited a complex dependence on sediment properties; the volume of CH4 and other gases were negligible in very coarse-textured sediment with low water and organic carbon contents. Gas volumes increased strongly with increased silt content, and were highest in sediments with intermediate water contents (60-70%), organic carbon contents (2-3%) and depths (approximately 4 m). Methane was the dominant gas collected from sediment (80 - 90%), while carbon dioxide comprised roughly 2 - 3% of sediment gas in the lake. Gas sampling during cool winter months found very low or undetectable volumes of gas present, while sediment gas volumes increased markedly during the spring and early summer months, and then declined in late summer and fall. The rate of CH4 ebullition, quantified with an echosounder, also varied markedly across the lake and seasonally. High rates of ebullition were measured at all 7 sites in July 2011 (up to 96 mmol CH4 m-2 d-1), while the rates were >50% lower in September and negligible in December 2010. Ebullition rates were inversely correlated with depth and most other sediment properties, but strongly positively correlated with sand content. No simple relationship between ebullition rate and sediment gas volume across the set of sites was found, although ebullition rates at individual sites were positively related to gas volume. Measurements of acoustic target strength of individual bubbles across the sediments and over time were also made. Bubble size and volume varied weakly across the different sediments and depths, with no strong correlation with sediment properties. A statistical characterization of the population of bubbles found broadly normally-distributed bubble size, with kurtosis values of -0.84 to +1.11 and skewness values of -0.23 to 0.62. The ensemble-average weighted mean bubble volume was 0.0940.023 cm3, although individual bubbles with target strengths as low as -68dB (0.0013 cm3) and as high as -43dB (4.689 cm3) were found.

The present dissertation is a collection of papers investigating the magnetic properties of sediments. The main aim of the work presented here is to study the magnetic characteristics of sedimentary deposits by using a methodology that efficiently quantifies the contributions of various ferrimagnetic components in sediments, and to exemplify how this model can be used to make inferences about past climatic and environmental variability. Magnetic minerals in sediments have long been used as indicators of variability in the factors controlling sediment deposition, and sediment-magnetic properties can be interpreted in terms of the processes controlling the fluxes of various magnetic components. Ferrimagnetic minerals, such as magnetite, are strong magnetically, and tend to dominate the signal from bulk measurements. Two sedimentary ferrimagnetic components that play a major role in shaping the magnetic record with time: a detrital component and a biogenic component. The detrital component of magnetic assemblages probably accounts for the greater proportion of the magnetic signal in many records, and therefore has been the focus of most environmental magnetism studies. The processes that control detrital records are mostly tied to local hydrology, climate, and vegetation cover. However, there is strong evidence that many magnetic assemblages are dominated by autochthonous magnetic particles, which in most cases are produced as a result of direct biologic control. Knowing the contribution of each of these components to the total mass of ferrimagnetic material becomes important when making inferences about past climatic or environmental conditions. The theoretical mixing model devised here using the characteristics of detrital and biogenic end members was tested on lake sediments from Minnesota. The analysis incorporates both spatial and temporal effects on magnetic record. We have investigated the history of sediment flux to Deming Lake, Minnesota, for the past 1000 years. Our results reveal several episodes of reduced precipitation, during which less sediment is mobilized from the catchment by overland flow and runoff. The most prominent episode occurred at the end of the Little Ice Age, indicating that this time period was not only cold but might have been drier than previously thought. The spatial control on sediment-magnetic properties was established via a survey of the magnetic properties of surface sediments from several Minnesota lakes. The magnetic properties are controlled by the competing fluxes of detrital and biogenic particles, according to location in the basin, while the position of the oxic-anoxic interface controls whether biogenic magnetite is formed in the sediment or in the water column, with implications in the preservation of intact versus collapsed bacterial chains. The thesis concludes with an incursion into the magnetic properties of chemical sediments from caves, or speleothems. The magnetic recordings preserved in calcite speleothems hold enormous potential for paleomagnetic and paleoenvironmental reconstructions. Speleothems lock in magnetization instantly, are not affected by post-depositional effects, and can be dated with high precision. The natural remanence in speleothems is carried mainly by magnetite, and the main remanence acquisition mechanism is depositional, through physical alignment of detrital magnetic grains parallel to the Earth's magnetic field. Future speleothem magnetism studies should benefit from increasingly sensitive magnetometers, operating at high spatial resolution, that are able to resolve short-term geomagnetic variability, and characterize events such as geomagnetic excursions at an unprecedented scale.

In Louisiana, the beds of natural lakes are owned by the state. The locations of property boundary lines separating state property from private lands have usually been set by determining the levels of natural monuments known as ordinary high water marks. The term is confusing and subjective, leading to controversy in reference to its determination. Catahoula Lake in central Louisiana was chosen as a study site because of its large size, its 20-foot variation in water levels, and its low-relief perimeter. Geology, geomorphology, hydrology, archaeology, vegetation, dendrochronology and dendrohydrology of the ancient cypress fringe, nineteenth century land survey records, historical records, and time-series statistics were applied to determine the elevation range of ordinary high water. Research suggests that the level of the ordinary high water natural monument used universally in Louisiana to define lake boundaries is not the correct natural monument. This research suggests that, for example, the natural monument that defines the Catahoula Lake boundary is not a vertical monument, but rather an areal monument that was originally recognized by nineteenth century U.S. government surveyors and embedded in the evidence extracted from their original field notes. The solution coincides with the boundaries of regional land patents and offers a consistent solution to determining the boundaries of thousands of acres of disputed lands. The procedure is applicable to other lake and swamp boundaries in Louisiana and other states.

The research studied a subterranean sediment deposit in an abandoned underground passage and soils from a sinkhole within the Scott Hollow drainage basin, Monroe County, southeast West Virginia. The purpose was to decipher how the lake formed, and the origin of the deposited sediment.Two excavations in the sinkhole overlying the eastern portion of the cave and a total of 11 samples were collected for study. 174 m of cave passage was mapped to delineate the morphology, calculate passage volume, volume initially covered by sediment and the current volume of sediment in place. Five profiles were made from the cave, and 32 sediment layers sampled. Grain size and environmental magnetic analyses were conducted. A composite stratigraphic column of the subterranean sediments was constructed to establish depositional sequence.The results indicated that the overlying soils form part of Teas-Calvin-Litz and Frederick-Duffield-Dunmore soil associations. The survey showed that lake was formed from partial conduit blockage by damming of the stream when the ceiling of the cave collapsed. 517 m3 of fluvial sediment was then deposited, of which 64% has since been eroded. There is currently 1398 m3 of open passage volume. The deposition was from two major hydrologic  ” depositional cut and fill phases resulting to the four sediment terraces. The lower terraces are younger than the upper terraces, as evidenced by the lower sediments lapping onto the upper terrace. Channel and wall irregularities and the breaching of the dam resulted in irregular deposition and erosion of the sediment.The environmental magnetic studies showed high magnetic mineral concentrations, abundant superparamagnetic grain fractions, and both low and high magnetic coercivity minerals. Correlation of the magnetic mineralogy, however, showed the subterranean sediment to be composed of high coercivity minerals (goethite) and the soils composed of low coercivity minerals such as magnetite. Although correlation of soils and cave sediment was not possible based on magnetic mineralogy, there existed a general correlation between the layers of sediment found within the stratigraphic column constructed from the cave sediment.The morphology of the cave and the sediment present substantiate that sediments were deposited due to partial conduit blockage from damming of stream. Grain size analyses indicate that samples are mainly of clay, silt, sand, pebbles and some cobble size fractions. Gravel mineralogy is shale and chert. Shales in the sediment and the cave wall are both fine grained and smooth in texture, with light  ” dark gray to greenish gray coloration. This is different from shales found in the soils which have light-gray color. Based on these findings, it can therefore be argued that gravels found in the cave sediment did not originate solely from outside the cave. The color of the samples was determined in-situ. This may have led to apparent differences in color due to variable moisture conditions. The hypothesis that cave sediments were derived from a sinkhole overlying the eastern environs could not be substantiated because of the imprecise correlation established between cave sediment and sinkhole soils. The cave sediments are likely autochthonous at least in part.

This thesis uses multiple regression analysis in the determination of two hedonic models to explain the impact that sedimentation and algal bloom events may have on property values along Lake Greenwood, SC. Utilizing different independent variables, the hedonic equations reflect the market value and the sales price of the selected lakeside properties. With an average 4.6 percent of the original lake area lost to accreted sediment, the models show a $7,800 to nearly $10,000 average loss in property value or an estimated $5 to $6 million in value lost within the study area. Properties sold within a two-year period following the major algal bloom event that occurred in 1999 are found to have sold for approximately $22,000 less than they would have during any other period. This equates to a loss of over $1.6 million among the parcels sold during this period.

The Eocene Green River Formation (USA) is one of the most extensively studied Konservat Lagerstätte in the world. Six species of ostracodes (Hemicyprinotus watsonensis, Candona pagei, Cypridea bisulcata, Metacypris paracordata, Potamocypris williamsi, and Procyprois ravenridgensis) were recovered from a 154 meter section of the Laney Member in the Washakie Basin. The ostracode species recovered comprise a variety of iological niches including plant and mud dwellers as well as nektonic lifestyles. These biological tolerances were used to reconstruct environmental conditions of the lake through its history. The ostracode response to the changing lake conditions within the Laney Member demonstrates an environmental tracking of balanced-filled to overfilled basin conditions. In addition, the similarity of ostracodes faunas between the Laney Member and those from the Uinta Basin supports the possible paleo-hydrologic connections of various basins within the Green River Formation, related to tectonic uplift and concomitant climatic change during the Eocene Thermal Maximum.

This thesis began with the goal of designing a bold house cantilevered over the edge of a cliff 120 feet above the water, and evolved into the study of how to design when starting with the primary form of a cube. The cube was chosen as representing the crystalline form of the rock upon which the house sits. The outside shell of the house is horizontal, board formed concrete, also in reference to the layered rock of the cliff face. There are two primary forces cutting away the mass of the cube to produce the final form of the house. The first force is of the site, and is generated by two spectacular views. These two views are used to cut through the house, forming an â Xâ shaped atrium eight feet wide and four storeys high, in the center of the house. The second force is generated by the desire to bring daylight into two opposite corners of the house. The southern corner of the house faces the lake. The bottom of that corner is cut out more than the top to admit direct sun in the winter, indirect sun in the summer, and reflected sun off the lake year round. The northern corner of the house faces the woods. The top of that corner is cut out more than the bottom to allow northern light into the top floors and maintain privacy on the lower floor, where the driveway approaches the house.

Implied spatial boundaries are examined and evaluated at a camping shelter complex on an Eastern California lake. A grid of concrete columns house a series of suspended wooden boxes and a connecting ramp.

Artificial destratification equipment was installed in Lake Samsonvale in October 1995 to reduce the biomass of potentially toxic cyanobacteria in the reservoir. This study was undertaken to investigate the effects of the destratifier on the limnological processes occurring in the lake and to determine if operation of the destratifier has been effective at reducing the summer populations of Cylindrospermopsis raciborskii and Microcystis aeruginosa. The study showed that artificial destratification of Lake Samsonvale has been successful at reducing the surface to bottom thermal gradient and increasing dissolved oxygen concentrations at depth. While the destratifier has not resulted in the lake becoming completely 'mixed' during summer, it has weakened resistance to mixing from meteorological events, which has led to a reduction in mean concentrations of total and dissolved phosphorus during summer. Although not conclusive, it is likely that the influence of the destratifier is restricted to a narrow radial distance around the bubbleplumes during periods of strong stability, so internal loading may continue to provide a substantial source of nutrients for cyanobacterial growth, particularly in regions of the lake less influenced by the destratifier. The results for cyanobacteria are less encouraging. Despite the reduction in concentrations of dissolved phosphorus, the destratifier has not been effective at reducing summer populations of C. raciborskii and M. aeruginosa. On the contrary, there is evidence to suggest that populations have actually increased which could have serious operational consequences for the lake by mixing the previously buoyant cyanobacteria to the level of the water off-take. The growth season for C. raciborskii has been extended by up to 3 months and population onset now occurs during spring. This increase in spring populations could be a result of significantly greater baseline populations during winter, or the earlier germination of akinetes as a result of increased sediment temperatures. The seasonal successional relationship between C. raciborskii and M. aeruginosa appears to have shifted from one of alternating dominance between the two species to one of co-existence under conditions of intermediate disturbance. It was concluded that although the continued operation of the destratifier may prove useful to minimise water treatment costs through reducing internal loading of dissolved constituents, it has not been successful in achieving its original objective of controlling cyanobacterial populations in the lake.

Annually laminated lake sediments provide detailed records of climatic variability and human activity in a watershed. Laminated lake sediments from Derby Lake, Michigan have been used to reconstruct Holocene climate variability for the last 8,600 years. Using a detailed grayscale record, spectral analysis shows distinct periods of variability centered at ∼250 and 44 years. These periodicities are similar to observed and inferred fluctuations in solar variability, and indicate that solar-climate linkages may be important factors governing regional climate. A sediment record from Crawford Lake, Ontario, Canada, has been used to reconstruct human activity in the watershed for the past ∼1000 years. The Crawford Lake watershed has long been of interest to archaeologists and anthropologists due to settlement by native Iroquois people in the mid 13 th century. Detailed fossil diatom assemblages reconstructed from Crawford Lake sediment show that diatom assemblages were extremely susceptible to human activity in the watershed. The diatom flora changed simultaneously with the arrival of humans in the watershed, despite very low numbers of people. The Crawford Lake record is unique in that nearly 400 years of lake recovery separate Iroquoian abandonment of the watershed and resettlement by Canadians in 1867 AD. The diatom flora, combined with a detailed geochemical record, show that despite decreased nutrient availability during this recovery phase, diatoms in Crawford Lake did not return to a pre-disturbance assemblage. Rather, diatoms maintained a meso-eutrophic assemblage throughout the recovery phase. Diatom community structure may be related to hysteresis, or non-linear behavior. The diatom community may have shifted to an alternative stable state following Iroquois village construction, thereby making recovery to pristine assemblages difficult or not possible.

TD-123

With a population estimate of 99 pairs, the Madagascar fish-eagle (Haliaeetus vociferoides) is one of the rarest birds of prey in the world. I investigated the ecological requirements of the Madagascar fish-eagle in 1994 and 1995 to help determine management action to prevent its extinction. I investigated fish-eagle foraging ecology in 1996 to determine its prey preference and whether fish abundance and availability affect fish-eagle foraging rates and foraging success. Madagascar fish-eagle nest and perch trees were taller, broader, had more unobstructed branches, and had a greater arc of accessibility than unused trees. Perch trees also were deciduous more often and had a narrower growth form than unused trees. Nest sites had more shoreline perch trees than unused sites. Lakes occupied by fish-eagles were deeper and clearer, and had more shoreline perch trees, more fish, a greater total fish weight, and more fish species than unoccupied lakes. I developed logistic regression models to predict the probability of Madagascar fish-eagle use based on the measured habitat variables. Nest and perch tree models included tree height. The nest site model included number of shoreline perches. Lake models included number of shoreline perches and either number of fish, total fish weight, or number of fish species. These models can be used to predict fish-eagle habitat use with > 70% accuracy. Introduced tilapia, Oreochromis spp. and Tilapia spp., made up the majority of both the gill net (66.3%) and fish-eagle catch (64.7%) in similar proportion, which suggests that the fish-eagle is an opportunistic predator. Replacement of native fish species by exotics, thus, probably has not been detrimental to the island's fish-eagle population. Male fish-eagle foraging success was positively correlated with number of fish, total fish weight, and number of fish species, which suggests that declines in the fish population could adversely affect the fish-eagle population. The results of this study indicate that Madagascar fish-eagles require bodies of water with large shoreline trees and an ample fish population. I recommend greater protection of aquatic habitats, monitoring and management of freshwater fish populations, and education of local people in sustainable tree harvesting practices.