A palaeolimnological study was carried out on a high-resolution, 7.62 m-long core (RU188-07) from northern Lake Rotorua, North Island. The core consists predominantly of olive diatomaceous ooze, laminated in places, and contains five tephras including Tarawera (1886 A.D.), Kaharoa (c. 1314 A.D.), Taupo (c. 233 A.D.) and Whakatane (c. 5500 cal. years B.P.). The core terminated in Whakatane Tephra giving the sediment a maximum age of 5530 60 cal. years B.P. An age model for the sediment was developed using tephrochronology. Radiocarbon dates obtained on the sediment returned ages too old because of contamination by old CO2 or CH4, or both. Investigations carried out on the core included spectrophotometric, sedimentological and geochemical analyses, and diatom identifications, which provided a number of proxies from which inferences were made about lake history, catchment development, and palaeoclimate since c. 5500 cal. years B.P. The laminations, evident only in the upper, post-Kaharoa Tephra part of the record, comprise alternations of thin, dark, detrital deposits and pale, relatively fine-grained diatom assemblages. Sediment geochemistry indicates that the Rotorua catchment has undergone several changes since c. 5500 cal. years B.P., alternating between periods of variable and stable environmental conditions. Following the Whakatane and Waimihia eruptions and up to approximately 3000 cal. years B.P., the catchment surrounding Lake Rotorua was rather unstable. Fluctuations in many of the proxies during this period are likely to be associated with a variable climate with periods of storminess, coinciding with the establishment of ENSO conditions in New Zealand. A notable feature of the record is two phases of stability, the first following the Taupo eruption (from c. 1700 cal. years B.P. to c. 630 cal. years B.P.) and the second from c. 580 cal. years B.P. to c. 300 cal. years B.P. The latest, most significant event in the catchment history of Lake Rotorua was the settlement by Polynesians. M.S. McGlone implied from pollen profiles (from Holden's Bay) that initial settlement took place around the time of the Kaharoa eruption (c. 630 cal years B.P.; c. 1314 A.D.), but the sediment chemistry and erosion profiles obtained here, from the northern part of Lake Rotorua, indicate that although there may have been some early clearing in the northern catchment for tracks or buildings, large-scale clearing in the area probably did not occur until considerably later, c. 300 cal. years B.P. Also contained within the sediments are three layers of reworked tephric material that probably originate from the transfer of coarse grained tephra from shallow to deeper water during large storms at c. 1300 cal. years B.P, c. 520 cal. years B.P, and c. 220 cal. years B.P. Each event coincides with storm events inferred from records from Lake Tutira in eastern North Island. Because of Lake Rotorua's inland position, these inferred storm events probably represent only the largest cyclonic events (e.g. ex-tropical cyclones).

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Graduation date: 1970

Thesis (Ph. D.)--Oregon State University, 1972. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Abstract Half a century after the Tanganyika sardine (Limnothrissa miodon Boulenger) was introduced into Lake Kivu, several aspects of metazooplankton ecology were investigated from January 2002 to June 2005 in the pelagic zone of the lake. As in other large lakes of the region, zooplankton in Lake Kivu is species-poor, and is dominated by copepods. In addition to three cyclopoid species, four cladoceran and 12 rotifer taxa were recorded. Zooplankton showed marked seasonal variation. Total crustacean abundance increased to a distinct dry season maximum (August-September), following the rise of phytoplankton production associated with deep vertical mixing. The three copepods and the most important cladoceran species exhibited different patterns of vertical migration, depending on their feeding habits, life stages and body size at the adult stage. The relatively small Tropocyclops confinis Kiefer was permanently present in the euphotic layer, while the largest copepod species, Thermocyclops consimilis Kiefer and Mesocyclops aequatorialis Kiefer, as well as the cladoceran Diaphanosoma excisum Sars, exhibited a typical diel vertical migration, with some differences among life stages. Total biomass of copepods in Lake Kivu (Mean= 0.3 g C m-2) is lower than in lakes Tanganyika and Malawi. Similarly, mean annual total production (8.3 g C m-2 y-1) is about three times as low as in lakes Malawi and Tanganyika. The ratio between phytoplankton production and zooplankton production is low (about 1.6 %), suggesting a low transfer efficiency at this food web level. As primary production is in the range found in the other large lakes of the region, it is suggested that the low total zooplankton biomass in Lake Kivu is related to the disappearance of Daphnia curvirostris Eylmann, which was likely the key grazer before the planktivorous fish introduction. The absence in Lake Kivu of a calanoid copepod species, which can more efficiently exploit phytoplankton production, may be another reason why carbon transfer efficiency between phytoplankton and zooplankton is low. Data analysis using multivariate methods showed that seasonal variations of the ratio mixed layer depth: euphotic depth (Zm:Zeu) is the key driving force influencing plankton dynamics via its influence on quantity and quality of zooplankton food resources. This suggests that mesozooplankton dynamics in Lake Kivu is essentially bottom-up controlled. Presently, the sole indication of a significant impact of L. miodon predation on zooplankton is the decrease of average body size of the cladoceran Diaphanosoma over time. Résumé Un demi-siècle après l’introduction de la sardine Limnothrissa miodon Boulenger, endémique du lac Tanganyika, plusieurs aspects de l’écologie du métazooplancton pélagique du lac Kivu ont fait l’objet d’investigations dans ce lac de janvier 2002 à juin 2005. Comme dans d’autres grands lacs de la région, le métazooplancton du lac Kivu présente une faible diversité spécifique. Il est dominé par trois espèces de copépodes cyclopoïdes. Quatre espèces de cladocères et 12 taxa de rotifères ont également été observés. Le zooplancton de ce grand lac présente des variations saisonnières marquées. L’abondance totale des crustacés présente un pic distinct vers la fin de la saison sèche (août - septembre), qui succède à un pic de phytoplancton. Les 4 espèces les plus abondantes montrent différents patrons de migration verticale, dépendant de leur régime alimentaire, du stade de développement et de la taille du stade adulte. Le plus petit copépode, Tropocyclops confinis Kiefer reste en permanence dans la zone photique alors que les 2 grandes espèces, Thermocyclops consimilis Kiefer et Mesocyclops aequatorialis Kiefer, ainsi que le cladocère Diaphanosoma excisum Sars, réalisent des migrations verticales journalières, dont l’amplitude varie selon le stade de développement des individus. La biomasse totale des copépodes (moyenne = 0.3 g C m-2) est plus faible que dans les lacs Tanganyika et Malawi. Une différence semblable a été observée pour la production totale annuelle qui est de 8.3 g C m-2 j-1, soit environ 3 fois moins que dans les deux autres grands lacs. Le rapport entre la production primaire phytoplanctonique et la production zooplanctonique est également faible (environ 1.6 %) ; indiquant une faible efficience de transfert à ce niveau du réseau trophique. Le fait que la production primaire du Lac Kivu soit du même ordre de grandeur que dans les autres grands lacs de la région suggère que les faibles valeurs de la biomasse totale du zooplancton sont une conséquence de la disparition de Daphnia curvirostris Eylmann, qui était sans doute le brouteur le plus efficace avant l’introduction de la sardine. L’absence au Lac Kivu d’une espèce de copépode calanoide, qui peut exploiter le phytoplancton de façon optimale, est sans doute une autre raison de la faible efficience du transfert de carbone entre le phyto- et le zooplancton. L’analyse des données par des méthodes multivariées a montré que la variation saisonnière du rapport zone de mélange: zone photique (Zm:Zeu) est le facteur clé influençant la production du métazooplancton via la quantité et la qualité de ses ressources alimentaires. La dynamique zooplanctonique dans ce lac subit donc essentiellement un contrôle « bottom-up ». La diminution de la taille des individus de Diaphanosoma au cours du temps est actuellement la seule indication de l’impact de la prédation de Limnothrissa miodon sur le zooplancton.

The Coyote Hills are located about 46 kilometers north-northwest of Lakeview, Oregon, within the Basin and Range physiographic province. These hills represent a complex volcanic center of bimodal calc-alkaline igneous activity. The oldest rocks recorded in the Tertiary succession are horn-blende- bearing andesite and aphanitic basalt flows, laharic breccias, conglomerates, tuffaceous sandstones, and lithic wackes of the late Eocene to early Oligocene Lower Andesite formation. During middle to early late Oligocene time, voluminous eruptions of predominately basaltic andesite formed a large shield volcano. This unit, the Upper Basalt formation, was followed, after a short hiatus, by the Coyote Hills rhyolite of late Oligocene to early Miocene age. The Coyote Hills rhyolite represents a complex spectrum of multi-phase silicic volcanism and comagmatic near-surface plutonism. Magma compositions varied from dacite to rhyolite and include lava flows, volcanic plugs, a flow dome complex, and a hypabyssal quartz monzonite intrusion. Volcanic activity that post-dates formation of the bimodal Coyote Hills complex culminated with the lower slopes of the shield volcano onlapped by the middle Miocene Steens Basalt, the late middle to early late Miocene Plush tuff, and the late Miocene to early Pliocene Upper basalt. A prominent northwest and northeast-trending fault and fracture system formed after emplacement of the Coyote Hills rhyolite, and as early as late Oligocene to early Miocene in time. Basin and Range faults post-date the Steens Basalt and have caused some minor displacement of the younger rocks. Penecontemporaneous with silicic volcanism of the Coyote Hills rhyolite was a period of hydrothermal activity. Fluids ascended favorable structures, altered the surrounding country rocks, and deposited minor quantities of epithermal gold-silver-copper-mercury-molybdenum(?)- lead(?), and zinc(?) in structurally controlled quartz-pyrite veinlets and as disseminations. Because of the association of mineralization with silicic volcanics in time and space, it is concluded that the two processes were genetically related. The hydrothermal system in the Coyote Hills is related to the late stages of silicic volcanism. Evidence for a genetic relation includes the close association of rock type, and chemical and mineral zonations within the district. Geological and geochemical evidence that includes rock type and alteration patterns, and mineral and trace element zonations, collectively suggest that only the highest level of the hydrothermal system has been exposed. It is entirely possible that a large vein or disseminated-type deposit containing both base and precious metals is present at depth. / Graduation date: 1981

The main objective of this study was to investigate small-bodied fish caging as an approach to evaluate selenium (Se) bioaccumulation and speciation in native fish species inhabiting lakes influenced by uranium (U) milling effluent in northern Saskatchewan, Canada. In contaminated environments freshwater fish show a high propensity to accumulate Se beyond levels needed for normal physiological function. Maternal transfer of elevated Se concentrations to offspring can cause deformities and reduced survival in fry, and in certain cases negatively impact the sustainability of native fish populations. This research included a caging validation study using wild, naïve (i.e., collected from a reference lake) lake chub (Couesius plumbeus) and spottail shiner (Notropis hudsonius), and three field based 21-day caging studies to investigate the dominance of the feeding pathway with respect to Se uptake and speciation in wild populations of northern small-bodied fish exposed to a gradient of Se. Three feeding regimes were used: an in situ benthic diet, a basal Se diet of Chironomus dilutus (1.5 µg Se/g dry weight) and a Se-spiked diet of C. dilutus (5.5 µg Se/g dry weight). Lake chub were identified as more suitable candidates for caging due to higher survival and condition factor at the completion of the in situ 21-day trial. The resulting Se bioaccumulation was compared among treatments as well as to wild small-bodied fish populations from the study area. Results from the caging experiments showed that caged lake chub exposed to natural and controlled diets with elevated Se had significantly greater whole-body Se concentrations after 21 days compared to fish caged in the reference lake. The results also showed that whole-body Se concentrations exceeded conservative Se thresholds, and approached the currently proposed USEPA regulatory threshold (7.91 µg/g dry weight) designed to protect fish species in only three weeks. The use of stable carbon (C), nitrogen (N), and sulphur (S) isotope ratios indicated that alternate benthic food sources native to the exposure lake were consumed in conjunction with the controlled diets. Stable isotope analysis of both wild and caged lake chub indicated that the N and S isotopic signatures decreased with increasing Se exposure, representing differences in isotopic signatures of the food sources. Speciation results from caged lake chub indicated that Se substituted for S in methionine (i.e. selenomethionine) was the dominant Se species found in caged lake chub exposed to dietary sources of elevated Se. Overall, this research demonstrates that using caged native lake chub represents a useful biomonitoring approach to investigate patterns of Se bioaccumulation and speciation in fish.

The lake sturgeon (Acipenser fulvescens), is a species with considerable ecological, social and economic value. Unfortunately, over-exploitation and habitat alteration have led to the collapse of lake sturgeon fisheries across North America. Based on conservation concerns, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) identified eight designatable units (DUs) among Canadian populations of lake sturgeon using the limited information available. These DUs are intended to represent taxonomically, genetically, geographically, or biogeographically distinct units below the species level. In this study, the genetic structuring among 20 lake sturgeon localities was examined using nine microsatellite loci. Lake sturgeon localities conformed to hierarchical partitioning of genetic diversity, with the greatest genetic divergence between localities in the Great Lakes and Hudson Bay drainages. Finally, minimal divergences among the current DUs warrant adjustment of lake sturgeon DU boundaries, to more appropriately reflect the distribution of genetic differentiation among lake sturgeon localities.

The lake sturgeon (Acipenser fulvescens), is a species with considerable ecological, social and economic value. Unfortunately, over-exploitation and habitat alteration have led to the collapse of lake sturgeon fisheries across North America. Based on conservation concerns, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) identified eight designatable units (DUs) among Canadian populations of lake sturgeon using the limited information available. These DUs are intended to represent taxonomically, genetically, geographically, or biogeographically distinct units below the species level. In this study, the genetic structuring among 20 lake sturgeon localities was examined using nine microsatellite loci. Lake sturgeon localities conformed to hierarchical partitioning of genetic diversity, with the greatest genetic divergence between localities in the Great Lakes and Hudson Bay drainages. Finally, minimal divergences among the current DUs warrant adjustment of lake sturgeon DU boundaries, to more appropriately reflect the distribution of genetic differentiation among lake sturgeon localities.

The purpose of the study was to investigate possible environmental impacts of a reduced catchment area (~25 %) for Kaunisjärvi lake and Patojoki river due to establishment of a iron ore mine in Kaunisvaara, Pajala municipality. To accomplish this, two methods were used; first a literary study was inducted to establish impacts of reduced inflow to lakes and reduced flow in rivers. Secondly, the state of the waters was determined by collecting background data from the mining company (Northland Resources SA) which included chemical- and biological parameters. The result showed that a reduced inflow can affect a lake by either eutrophication or oligotrophication, depending on the lakes condition and the character of the inflow, which in turn has impacts on the entire food-web. Reduced flow in rivers also has impacts on the entire food-web by increased water temperature, decreased dissolved oxygen levels, decreased inundation (witch effects nutrient and organic material exchange), decreased biodiversity in phytoplankton, benthos and fish and inhibiting migration, studies differed in effects on pH and alkalinity. The result also showed that both Kaunisjärvi and Patojoki are affected by nutrient load and organic matter, which impacts the entire ecosystem of the waters. Possible consequences for Kaunisjärvi and Patojoki of reduced inflow and reduced flow are discussed. The report concluded that the reduced catchment area will have impacts on environmental goals set by EU and also on national level, but that the interest of exploitation weighs higher.