Thesis (Ph. D.)--Michigan State University. Dept. of Fisheries and Wildlife, 2008. / Title from PDF t.p. (viewed Sept. 11, 2009). Includes bibliographical references. Also issued in print.

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Eutrophication is a global environmental problem, which in Sweden is predominantly in the south of Sweden where there are large agricultural areas. Skellefteå is a small town on the northern coast which has eleven water bodies classified as “poor ecological status” of which Uttersjöträsket is one of them according to the water authorities. Uttersjöträsket has a requirement to achieve good ecological status by 2021. Uttersjöträsket’s agriculture land is from at least 1716 according to historical maps. To be able to restore a eutrophic lake the source of the phosphorus load must be identified.To determine the natural state for Uttersjöträsket the sediment record could be studied. For example, earlier studies have been made in Kassjön in Umeå were they conclude that the beginning of the agriculture area started in the 12th century, which means that Uttersjöträsket could have had agriculture land since before 1716. The municipality of Skellefteå made contact with residents in the area who formed a water group to work towards achieving the goal by 2021. This report will form the basis for the water group to take appropriate measures to reduce the bloom of cyanobacteria and to achieve good ecological status. The conclusions of this report are based on analysis of data and results from previous studies of eutrophic lakes. Many different methods must be done to have a long-lasting impact and to achieve good ecological status in Uttersjöträsket. The focus of the actions should be on the ditch between Yttersjön and Uttersjöträsket as the highest phosphorus load is in that catchment.

Master of Arts / Department of Geography / Kendra K. McLauchlan / The importance of local parent material has been recognized as a fundamental control on the geochemistry of lake sediments, but there have been relatively few broad-scale surveys of catchment sources of terrigenous lake sediments. In this paper, I present a geochemical study of catchment parent materials and lake sediments from four lakes in Northern Minnesota. Similar climate and vegetation conditions are present at all four lakes, which vary mainly in catchment parent material and lake morphometry. Geochemical data including major, trace and rare earth elements (REEs) from catchment parent material samples was compared with lake sediment geochemical data using PCA, linear regression, geological indices and elemental ratios. In homogenous till-dominated catchments, patterns of elemental variation in the catchment till could be extended to predict elemental concentrations in the lake sediments. Simple ratios, which are commonly used to analyze lake sediment geochemical data, were not good predictors of lake sediment composition, however. Catchments with mixed bedrock and till were compositionally heterogeneous, and comparison with lake sediments was difficult. Lack of grain size control and biogenic silica measurements further confounded analysis. However, ΣREE/Y ratio was found to be diagnostic of the catchment parent materials and present within the lake sediments. This study makes a contribution to an improved understanding of lacustrine sedimentary archives by analyzing the spatial linkages among catchment, water and sedimentary geochemistry.

The purpose then of this paper has been to expand our knowledge of these aquatic forms by investigating the cultural, physiological, morphological, and chemical characteristics of an actinomycete isolated from the water supply, Lake Waco, of Waco, Texas.

Both travel times and amplitudes of large offset refracted and reflected arrivals observed during GLIMPCE (Great Lakes International Multidisciplinary Program on Crustal Evolution) along line A in Lake Superior have been modeled using two-dimensional ray tracing techniques. Forward modeling was used to iteratively refine an initial velocity model that was constructed from results of tau-sum analysis of the travel time data at each station combined with information from the coincident common depth point (CDP) reflection profile. When converted to time the resulting model agrees quite well with the CDP reflection profile. A 50-100 ms time advance anomaly associated with the Isle Royal Fault is observed at every station. This anomaly has been modeled as shallow, high velocity blocks located directly beneath the fault. The blocks correlate well with the walls of a steep-sided bathymetric trough and are believed to represent highly indurated upper Keweenawan sediments which may have resulted from hydrothermal alteration. Approximately 2 km of sedimentary rock (2.8-4.6 km/sec) overlie an 8 km thick sequence of volcanics and interflow sediments (5.0-6.5 km/sec) within the rift graben observed on the reflection data. Beneath this sequence is a 6-8 km thick sequence of 6.6-7.0 km/sec material that is interpreted to represent metamorphosed volcanics. The velocity of the material at the base of the rift graben is not well constrained (approximately 7.0 -7.2 km/sec), but probably comprises an additional 10-12 kilometers of meta-volcanic rocks and intrusions that extend to the base of the graben as imaged on the CDP reflection profile. Boundaries between these sequences are indicated by reflections observed at several of the wide-aperture stations. A marked decrease in the apparent velocity and amplitude of the first arrivals is observed on reversed sections at ranges exceeding 100 km. This decrease in apparent velocity has been modeled as lower velocity continental crustal rocks (approximately 6.5 km/sec) at a depth of about 15-20 km adjacent to the 7.0 km/sec material in the graben. Calculation of the gravity response of the seismic model demonstrates that the gravity high centered over the rift can be entirely attributed to high density rocks occupying the central half-graben imaged on the CDP profile. Wide angle reflections from about 15-30 km depth beneath the flanks of the graben indicate the presence of velocity discontinuities that may represent rift related detachment surfaces and/or pre-rift structures. Modeling of wide angle reflections indicate a high degree of structural relief preserved within the lower crust. The high velocities modeled for this region, coupled with information from the CDP profile, suggest that the lower crust represents Archean crust that has been either heavily intruded or underplated by mafic magma. The style and volume of volcanic emplacement is similar to that of Phanerozoic rifted continental margins and flood basalt provinces. By analogy, the volcanism within the midcontinent rift appears to have resulted from decompression melting during lithospheric extension above a broad, asthenospheric thermal anomaly recently referred to in the literature as the "Keweenawan hot spot". / Graduation date: 1991

The subjects for this study are two subglacial lakes -- Vostok and Concordia -- located in East Antarctica. Lake Vostok is the largest known subglacial lake on Earth. Melting and freezing at the ice-water contact are known to occur in both lakes. These internal processes are important subjects for numerical modeling. The precise knowledge of the lake's bathymetry and the distribution of unconsolidated sediments at the bottom of the lake are required boundary conditions for such modeling. The ultimate goal of this research was to develop 3D bathymetry models and to establish the distribution of unconsolidated sediments for both lakes. Joint interpretation of airborne gravity and seismic data was performed for Lake Vostok, revealing that the lake is hosted by consolidated sedimentary rocks. The modeling shows that Lake Vostok consists of two sub-basins: a larger, deeper one with water thickness exceeding 1000 m in the south and a shallower one with a water thickness of about 250 m in the north. The resulting 3D model has a substantially better correlation with seismic data than two previous models. Lake Concordia appears to be significantly shallower with water thicknesses not exceeding 200 m for all possible host rock densities. Since the lake is relatively shallow, the sediment layer cannot be resolved. A similar pattern of freezing and melting was observed in Lake Concordia and Lake Vostok: the deeper part of the lake lies under thinner ice and is dominated by the freezing of water at the ice bottom, while in the shallower part of the lake the overlying thicker ice melts. The analysis of seismic data in four different locations over Lake Vostok revealed the presence of unconsolidated sediments at the bottom of the lake. The sedimentary layer appears to be thicker (up to 400 m) in the northern basin, while its thickness does not exceed 300 m in the southern one. Four different sedimentation mechanisms were considered to explain how such a thick sedimentary layer was deposited in Lake Vostok under glacial conditions. The estimates show that none of the mechanisms considered is capable of depositing the observed sedimentary layer, revealing the pre-glacial origin of Lake Vostok.

Hypotheses regarding the distribution, texture and trace element concentrations of lake sediments were tested by empirical analyses of multi-lake data sets (52 to 83 lakes). Sediment distribution was best characterized by the deposition boundary depth (DBD), the abrupt transition from coarse- to fine-grained sediments. The DBD can now be predicted from either empirical models or empirical-theoretical simplifications of wave of sediment threshold theory, both in terms of exposure (or fetch) and bottom slope. The texture (organic content, water content and bulk density) of profundal sediments was related to the inorganic sedimentation rate and exposure, but not to the lake trophic status or the net organic matter sedimentation rate. The relationships between sediment texture and intra- and inter-site variability, together with the models that predict the DBD and sediment texture, were used to develop an algorithm that should greatly reduce sampling effort in lake sediment surveys. Finally, sediment trace element concentrations were predicted from sediment texture, site depth and simple geologic classifications. The models developed here, provide a framework in which to sample lake sediments and interpret their properties.

Thesis (M.S.)--University of Wisconsin--Stevens Point., 2007 / Includes bibliographical references (leaves 102-112).

Thesis (M.A.I.S.)--Oregon State University, 1997. / Typescript (photocopy). Includes bibliographical references. Also available online.