Thesis (Ph. D.)--Albert-Ludwigs-Universität zu Freiburg i. Br., 1978. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 161-184).

Thesis (M.A.)--Louisiana State University, 1959. / HTML version of 1959 thesis. Last viewed 3/26/2009. Vita. Includes bibliographical references (leaves 66-69).

This thesis presents the results of a three year study devoted to discovering the life and phenomena found in Lake Worth near Fort Worth, Texas.

The Canterbury Region is susceptible to a variety of natural hazards, including earthquakes, landslides and climate hazards. Increasing population and tourism within the region is driving development pressures and as more and more development occurs, the risk from natural hazards increases. In order to avoid development occurring in unacceptably vulnerable locations, natural hazard assessments are required. This study is a reconnaissance natural hazard assessment of Lakes Lyndon, Coleridge and Tekapo. There is restricted potential for development at Lake Lyndon, because the land surrounding the lake is owned by the Crown and has a number of development restrictions. However, there is the potential for conservation or recreation-linked development to occur. There is more potential for development at Lake Coleridge. Most of the land surrounding the lake is privately owned and has less development restrictions. The majority of land surrounding Lake Tekapo is divided into Crown-owned pastoral leases, which are protected from development, such as subdivision. However, there are substantial areas around the lake, which are privately owned and, therefore, have potential for development. Earthquake, landslide and climate hazards are the main natural hazards threatening Lakes Lyndon, Coleridge and Tekapo. The lakes are situated in a zone of active earth deformation in which large and relatively frequent earthquakes are produced. A large number of active faults lie within 15 km of each lake, which are capable of producing M7 or larger earthquakes. Ground shaking, liquefaction, landslides, tsunami and seiches are among the consequences of earthquakes, all of which have the potential to cause severe damage to lives, lifelines and infrastructure. Landslides are also common in the landscape surrounding the lakes. The majority of slopes surrounding the lakes are at significant risk from earthquake-induced failure under moderate to strong earthquake shaking. This level of shaking is expected to occur in any 50 year period around Lakes Lyndon and Coleridge, and in any 150 year period around Lake Tekapo. Injuries, fatalities and property damage can occur directly from landslide impact or from indirect effects such as flooding from landslide-generated tsunami or from landslide dam outbreaks. Lakes Lyndon, Coleridge and Tekapo are also susceptible to climate hazards, such as high winds, drought, heavy snowfall and heavy rainfall, which can lead to landslides and flooding. Future climate change due to global warming is most likely going to affect patterns of frequency and magnitudes of extreme weather events, leading to an increase in climate hazards. Before development is permitted around the lakes, it is essential that each of these hazards is considered so that unacceptably vulnerable areas can be avoided.

The species compositions and densities of the littoral and pelagic zooplankton assemblages in Crater Lake were compared. The littoral and pelagic zooplankton assemblages of most lakes are typically different due to different habitat conditions in the two zones. The littoral zone of Crater Lake lacks many of the habitat characteristics, which distinguish a typical littoral zone from the pelagic zone. In fact, none of the water quality variables measured differed significantly between the littoral zone and epilimnion of the pelagic zone in Crater Lake. The littoral and pelagic zones of Crater Lake were sampled with twelve paired sites in August and again in September of 1995. For the purposes of this study, the littoral zone was defined as lakeward from the shoreline to the 10m depth contour. At each paired site the pelagic assemblage was sampled to a depth of 120m at the 200m depth contour. Despite the almost identical water quality between the pelagic and littoral zones of Crater Lake, lack of vascular macrophytes in the littoral zone, and well-mixed epilimnion, the littoral zooplankton assemblage differed from the pelagic assemblage in both species composition and density. Several ubiquitous zooplankton taxa dominated both the littoral and pelagic zooplankton assemblages, although the density of these taxa as well as the relative abundance of these taxa differed between zones. These ubiquitous species reached their maximum densities in the metalimnion of the pelagic zone at a depth range of 10 to 60 meters below the lake surface and were considered primarily pelagic. A shift in wind direction between sampling periods influenced the distribution of pelagic zooplankton taxa in the littoral zone. Twenty-four taxa were recorded in the littoral zone, and aside from infrequent exceptions, none of these taxa were found in the pelagic zooplankton assemblage. Most of the littoral taxa were primarily adapted to the benthic zone. / Graduation date: 1999

Waldo Lake, located in the Oregon Cascades, is considered to be one of the most dilute lakes in the world. Even with very low nutrient concentrations and sparse populations of zooplankton, introduced fish in the lake are large in size and in good condition when compared to fish from other lakes. Fish were originally stocked in Waldo Lake in the late 1800's. The Oregon Department of Fish and Wildlife began stocking in the late 1930's and continued stocking until 1991. Species existing in Waldo Lake today include brook trout, rainbow trout, and kokanee salmon. The overall objective of this thesis was to increase the understanding of the interrelationships that affect the age, growth, and diet of fish in Waldo Lake. The specific objectives were to summarize and synthesize available information on the substrate, climate, water, and biota of the Waldo Lake Basin; describe the cultural history and current cultural values of the Waldo Lake Basin; determine the age, growth, length, weight, condition, diet, and reproduction of introduced fish species in Waldo Lake; interrelate the above information to show how these components of the natural-cultural system are related. Fish were collected one week per month from early June through mid-October in 1992 and 1993. Variable mesh experimental gillnets set in nearshore areas were used to capture fish in 1992. During the 1993 sampling period, experimental gillnets and trapnets were set in the nearshore areas of the lake. Relative age specific growth rates of brook trout in Waldo Lake are comparable to brook trout growth rates in other lakes. Brook trout growth rates generally decreased with age, however, there were no significant differences in the growth rate of each age class between 1991 and 1993. The condition of brook trout in Waldo Lake is also comparable to brook trout in other lakes. The same is true for rainbow trout and kokanee salmon. Fish in Waldo Lake are large in size and in good condition due, in part, to the availability of benthic macroinvertebrates. Taxa found in stomach contents of fish captured in Waldo Lake consisted primarily of aquatic benthic macroinvertebrates, but terrestrial vertebrates and vertebrates, although infrequently consumed, were also part of the total diet. Rainbow trout in Waldo Lake consumed primarily chironomidae larvae and pupae although odonata larvae, ephemeroptera larvae, and amphipods were also consumed. Kokanee salmon fed almost exclusively on chironomid larvae although small numbers of ephemeroptera larvae, odonata larvae, and coleoptera were also consumed. The most important macroinvertebrate taxon consumed by Waldo Lake brook trout was chironomid larvae and pupae, although other species also were important. The diet of Waldo Lake brook trout varied in a complex way that appeared to be related to the relative abundance of macroinvertebrate taxa, feeding location in the lake, and time of year. Brook trout diet also varied by size class. The components of the Waldo Lake natural-cultural system are complexly interrelated and the nature of these relationships are constantly changing. Each component in some way affects and is, in turn, affected by each of the other components. Changes in some components, such as substrate, affect other components along geologic time scales. Other components, such human culture and biota, may change rapidly within a decade. The capacity of natural-cultural systems, such as Waldo Lake, to change over time makes it possible to view the present state of the system only as a snapshot in time. This dynamic nature of the Waldo Lake natural-cultural system is not unique to Waldo Lake, but is expressed in all natural- cultural systems. / Graduation date: 1997

Approximately 14,500 years ago, Pleistocene Lake Bonneville discharged 4750 km 3 of water over the divide between the closed Bonneville Basin and the watershed of the Snake River. The resulting flood, emanating from the divide at Red Rock Pass, Idaho, followed the present courses of Marsh Creek, the Portneuf River, and the Snake and Columbia Rivers before reaching the Pacific Ocean. For the 1100 kilometers between Red Rock Pass and Lewiston, Idaho, the Bonneville Flood left a spectacular array of flood features that have allowed for geologic reconstruction and quantitative evaluation of many aspects of the flood hydrology, hydraulics, and sediment transport. Geologic evidence of maximum flood stages in conjunction with step-backwater modeling provides for peak discharge estimates and understanding of local hydraulic flow conditions for ten separate reaches along the flood route. Peak discharge was approximately 1.0 million m³•sec⁻¹ at the Lake Bonneville outlet near Red Rock Pass. Downstream, the maximum discharge had attenuated to 0.57-0.62 million m³•sec⁻¹ by arrival at Lewiston. Attenuation was primarily the result of flow storage in the wide alluvial valleys of the western Snake River Plain. The local hydraulic conditions (depth and velocity) of the Bonneville Flood varied significantly within and between the study reaches. The rate of energy expenditure was also highly varied; local calculated stream-power values ranged from less than 10 watts•m² to 100,000 watts•m². Greater than 60% of the total energy loss at peak discharge was expended in a total distance that encompassed less than 10% of the flood route. These spatial variations in local hydraulic conditions were profoundly important in controlling the distribution of flood processes and features. The deposition of tractively-transported cobbles and boulders (measured diameters ranged from less than 10 cm to greater than 10 m) occurred in reaches of decreasing flow energy within quantitatively-definable limits of flow energy. Areas of erosion are more difficult to precisely evaluate; however, they were restricted to reaches of greater stream power. It is likely that cavitation was an important erosional agent in many areas of most intense flow conditions.

Submerged macrophyte beds provide a secondary realm of accumulation in lakes. Particles otherwise destined to reside in the deep-water profundal zone are intercepted by nearshore macrophyte communities that attenuate wave and current energy. The microenvironment found inside submerged macrophyte beds can be substantially more quiescent than that of the open-water, allowing for fine particles to be deposited out of the water column. Together with larger, eroded inorganic sediments and coarse organic particles, these materials comprise the sediments underlying macrophyte communities. / Thirty-four littoral sites were sampled in Lake Memphremagog (Quebec-Vermont) to quantify the role of morphometry (littoral slope and site exposure) and macrophyte beds (mean biomass and biomass density) on the accumulation of sediments. An established historical marker, stable Pb, was used to date the sediments (approx. 110 years) and calculate rates of accumulation (SARs). Identifiable stable Pb profiles were obtained at two-thirds of the sites confirming the utility and robustness of littoral sediment core analysis. Multiple regression analyses showed that macrophyte parameters were the best predictors of SARs. Macrophyte mean biomass and biomass density were clearly most important in predicting the volume (total SAR) and organic content (organic SAR) of the sediments ($R sp2=0.57 rm to 0.76$, $P<0.001$). The same macrophyte parameters, however, poorly predicted the bulk (mainly inorganic) accumulation of sediments. Biomass density was solely related to the long-term accumulation of stable Pb in the sediments supporting empirical models that credit growth form as an important factor explaining among species or among weedbed variability in sediment-plant tissue elemental concentrations. The quantification of SARs will benefit both lakewide modeling of nutrient and contaminant budgets, and the understanding of littoral succession and its contribution to lake ontogeny.

Lake Ellesmere/Te Waihora is one of New Zealand’s largest coastal, brackish water lakes. It has nationally significant wetland bird populations and is regionally important for iwi. The lake regularly experiences fluctuations in water level, resulting in a continually expanding and contracting littoral zone. This study investigated the impacts of these water level changes on the ecology of the lake. Water chemistry results collected over 12 months, confirm the lake is hypertrophic, due to high nutrient (nitrogen and phosphorus) concentrations resulting in high chlorophyll a levels and low water clarity. Water chemistry conditions were collected at five locations around the lake and showed marked spatial variation, with the eastern most end (Kaituna Lagoon) having generally the best water quality and lowest salinity (mean 4.9 ppt). Mean concentrations of total nitrogen ranged from 1.63 to 2.4 mg/L, chlorophyll a from 50 to 148 ug/L and total suspended solids from 151 – 248 mg/L. Seasonally, highest nutrient concentrations (mean, total nitrogen = 2.625 mg/L, dissolved reactive phosphorus = 0.059 mg/L and total phosphorus = 0.365 mg/L) occurred in late summer months (February – March), slightly decreasing but remaining high throughout winter. The benthic invertebrate community was surprisingly diverse, Crustacea (Paracorophium excavatum), Oligochaeta, Mollusca (Potamopyrgus antipodarum) and Chironomidae (Chironomus zealandicus) were dominant community members in the littoral zone, although 24 other taxa were collected. At high water levels, taxonomic richness increased in the eulittoral zone, while decreasing in the mid-littoral and lower littoral zones. In contrast, density decreased with higher water level in the eulittoral and mid-littoral zones, while increasing in the lower littoral zone. Benthic invertebrate communities appeared to be adapted to periods of intermittent dewatering, and even sustained dewatering under cooler temperatures. Despite the relatively high diversity of benthic invertebrates, invertebrate predators are generally absent from the lake. My results suggest multiple factors and interactions from predation pressure, salinity and lack of macrophytes are likely responsible for the absence of predatory invertebrates such as damselfly (Xanthocnemis zealandica) and dragonfly (Procordulia grayi) larvae. The lack of significant relationships between water quality variables and water level, and the positive relationship between chlorophyll a and salinity, suggests that current lake opening events do not have a positive effective on either water quality or phytoplankton biomass in Lake Ellesmere/Te Waihora. However, the current lake opening regime seems to be favourable to benthic invertebrate survival in the littoral zone, as the lake is predominantly open over winter when temperatures are lower, reducing the risk of desiccation. Anthropogenic activities which modify hydrodynamic and water quality conditions can potentially have a large negative impact on the structure and diversity of the littoral invertebrate community as well as flow on effects through the lake food web. Based on results from this study, I suggest a minimum lake level at Taumutu of 0.6 m during the months from November – April in order to protect benthic invertebrate communities in the eulittoral zone from extensive loss of habitat, extreme temperature and reduced risk of desiccation. Having a minimum set at ~0.6 m would provide sufficient littoral zone habitat for the lakes extensive bird life and fish populations. In addition, immediate efforts are needed into reducing nutrient loads into the lake, through improved farm management (nutrient and stocking budgets) and riparian fencing. Furthermore, physical and chemical water quality properties would benefit from an increased water level over summer months, by reducing water temperatures, diluting readily available nutrient concentrations and potentially reducing phytoplankton (and potentially toxic cyanobacterial) blooms.

The Canterbury Region is susceptible to a variety of natural hazards, including earthquakes, landslides and climate hazards. Increasing population and tourism within the region is driving development pressures and as more and more development occurs, the risk from natural hazards increases. In order to avoid development occurring in unacceptably vulnerable locations, natural hazard assessments are required. This study is a reconnaissance natural hazard assessment of Lakes Lyndon, Coleridge and Tekapo. There is restricted potential for development at Lake Lyndon, because the land surrounding the lake is owned by the Crown and has a number of development restrictions. However, there is the potential for conservation or recreation-linked development to occur. There is more potential for development at Lake Coleridge. Most of the land surrounding the lake is privately owned and has less development restrictions. The majority of land surrounding Lake Tekapo is divided into Crown-owned pastoral leases, which are protected from development, such as subdivision. However, there are substantial areas around the lake, which are privately owned and, therefore, have potential for development. Earthquake, landslide and climate hazards are the main natural hazards threatening Lakes Lyndon, Coleridge and Tekapo. The lakes are situated in a zone of active earth deformation in which large and relatively frequent earthquakes are produced. A large number of active faults lie within 15 km of each lake, which are capable of producing M7 or larger earthquakes. Ground shaking, liquefaction, landslides, tsunami and seiches are among the consequences of earthquakes, all of which have the potential to cause severe damage to lives, lifelines and infrastructure. Landslides are also common in the landscape surrounding the lakes. The majority of slopes surrounding the lakes are at significant risk from earthquake-induced failure under moderate to strong earthquake shaking. This level of shaking is expected to occur in any 50 year period around Lakes Lyndon and Coleridge, and in any 150 year period around Lake Tekapo. Injuries, fatalities and property damage can occur directly from landslide impact or from indirect effects such as flooding from landslide-generated tsunami or from landslide dam outbreaks. Lakes Lyndon, Coleridge and Tekapo are also susceptible to climate hazards, such as high winds, drought, heavy snowfall and heavy rainfall, which can lead to landslides and flooding. Future climate change due to global warming is most likely going to affect patterns of frequency and magnitudes of extreme weather events, leading to an increase in climate hazards. Before development is permitted around the lakes, it is essential that each of these hazards is considered so that unacceptably vulnerable areas can be avoided.