Thesis (Ph. D.)--University of Wisconsin. / Vita. Description based on print version record. Includes bibliographical references.

Transformation of counts and weights of bottom fauna to either logarithims or square roots was required before application of statistical analyses. Preliminary analyses indicated that variability associated with relatively restricted sampling in a large lake prevented reliable evaluation of the bottom fauna while variability evident in extensive sampling from a large lake was not so great as to prevent reasonably precise estimation of abundance. Further analyses showed that the degree of variability was affected by regional location, depth, changes in abundance of the fauna, and qualitative composition of the fauna. Examination of factors contributing to sampling variability showed that operation of the Ekman-Birge dredge, distinction and delimitation of sampling zones in respect to depth and bottom substrate, diurnal and seasonal changes, and the size of samples all were of importance. The use of Ekman-Birge dredge with more powerful jaws in conjunction with more rigorous horizontal and vertical stratification of sampling was suggested as a means of reducing extreme variability in sampling. A 70 per cent sodium silicate solution was found to provide an effective separation of bottom organisms from certain types of substrate. Predation by fish was suggested as responsible for the significant littoral minimum evident in abundance of bottom organisms in Hatzic lake. / Science, Faculty of / Zoology, Department of / Graduate

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Source: Dissertation Abstracts International, Volume: 37-01, Section: B, page: 0074. / Thesis (Ph.D.)--The Florida State University, 1976.

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The toxin-producing potential of some freshwater cyanobacterial species and their ability to form dense blooms makes the possibility of an increase in their biomass of concern to lake managers and the general public. Modelling of cyanobacterial biomass and dominance in inland water bodies has demonstrated that cyanobacterial biomass increases concomitantly with nutrients in freshwater systems. Though temperature and water-column stratification are increasingly cited as factors promoting cyanobacterial biomass, support for this has been mainly provided by laboratory studies and individual lake studies. Furthermore it is not well known if models developed across large spatial gradients perform adequately at regional scales where responses could be modulated by additional unconsidered regionally-distinct variables. This thesis evaluates the effects of temperature, nutrients and other predictors on cyanobacterial biomass in North American lakes, through general models and when accounting for water body type and region of origin. A novel analysis of an existing dataset comprising single sample dates of over 1000 lakes in the United States showed that temperature was a significant predictor of cyanobacterial biomass. The effect of temperature was shown to be independent of those of nutrients and increases in total phytoplankton biomass. This suggests that warming alone might result in an increase in cyanobacterial biomass in lakes. The effects of the different variables varied between the lake systems considered (deep or shallow; natural lake or reservoir) with the strongest relationships found in deep natural lakes. An unpublished dataset of 88 Canadian lakes was used to test the effects of nutrients and temperature across regions using seasonally averaged data. These robust models provide some support for differing responses among regions, suggesting caution when applying general models to specific regions. Additionally, cyanobacterial genera biomass distribution in lakes was found to be explained by multiple environmental variables. Generally, nitrogen was found to be a significantly better predictor of cyanobacterial biomass than total phosphorus suggesting that nitrogen-fixation by cyanobacteria is less prevalent that previously estimated. Together, this thesis advances our understanding of the variables driving cyanobacterial biomass in lakes and demonstrates that under continued nutrient enrichment and warming temperatures increases in cyanobacterial biomasses in North American lakes could be expected. / Les proliférations de cyanobactéries sont des sujets de préoccupation à l'échelle globale en raison de leur capacité de former des écumes denses qui épuisent l'oxygène dissoute et qui peuvent produire des toxines, nuisant à l'utilisation des plans d'eau tant pour l'eau potable que les loisirs. La modélisation de la biomasse et de la dominance des cyanobactéries a préalablement démontré que leur abondance augmente de façon concomitante avec les nutriments dans les systèmes d'eau douce. Bien que la température et la stratification de la colonne d'eau soient de plus en plus citées comme facteurs favorisant la prolifération des cyanobactéries, ces associations sont surtout basées sur des études en laboratoire et de lacs individuels. En outre, il n'a pas été bien démontré que les modèles développés sur d'importants gradients spatiaux s'appliquent de façon adéquate à l'échelle régionale, où la biomasse pourrait aussi être modulée par des variables additionnels. Cette thèse évalue les effets de la température, des nutriments et d'autres prédicteurs sur la biomasse des cyanobactéries dans les lacs d'Amérique du Nord, à travers le développement de modèles général ainsi que des modèles tenant compte des spécificités régionales. Dans le premier chapitre, je présente une analyse exhaustive d'un ensemble de données de plus de 1000 lacs. Utilisant cet ensemble de données, où la plupart des lacs ont été échantillonnés une seule fois au cours de la saison de croissance, j'ai démontré que les concentrations de nutriments (azote et phosphore) et la température étaient des prédicteurs significatifs de la biomasse des cyanobactéries. L'effet de la température sur la biomasse des cyanobactéries est statistiquement indépendant de celui des nutriments. Ces résultats suggèrent que le réchauffement des eaux de surface pourrait entraîner une augmentation de la biomasse des cyanobactéries dans les lacs. Les effets des variables différaient entre les systèmes étudies (profonds, peu profond ; lac naturel, réservoir). Les meilleurs modèles ont été développés pour lacs naturels profonds. Dans le deuxième chapitre de cette thèse, j'ai examiné un ensemble de données inédites basées sur les moyennes saisonnières de 88 lacs provenant de trois régions du Canada (l'Alberta, la Colombie-Britannique et l'Ontario). J'ai développé des modèles prédictifs généraux et examiné comment les modèles pouvaient différer entre les régions en utilisant la modélisation linéaire générale et la modélisation à effets mixtes. Les prédicteurs environnementaux ressortant furent similaires à ceux du premier chapitre mais, tel qu'attendu, les modèles utilisant les moyennes saisonnières expliquèrent une plus grande proportion de la variance de la biomasse des cyanobactéries car elles sont plus représentatives. Ces modèles ont aussi relevé des différences claires entre l'Ontario et les autres provinces mais l'inclusion d'avantage de lacs de l'Ontario dans l'analyse serait nécessaire afin de résoudre pourquoi c'est le cas. Dans l'ensemble, cette thèse enrichit notre compréhension des variables influençant la prolifération des cyanobactéries dans les lacs. Elle démontre clairement que, par l'enrichissement continu en nutriments et le réchauffement des eaux de surface, une augmentation de la biomasse des cyanobactéries dans les lacs nord-américains serait attendue.

Forty-five lakes in Killarney Provincial Park and the surrounding area in south-central Ontario, Canada, were sampled for crustacean zooplankton and water chemistry in the summer of 2005. For each of the lakes, we had historic data from peak-acidification in the 1970s and post-acidification periods in 1990 and 2000. Situated among the orthoquartzite ridges of the La Cloche Mountains in and near Killarney Provincial Park, many of these lakes were acidified during the mid-1900s owing to extensive mining and smelting activities in nearby (40-60 km) Sudbury, Ontario. There is large variation in the geochemistry of the soils and the bedrock within the park. As a result, these freshwater lakes have varying degrees of acidification, ranging from being heavily acidified (pH < 4.5) to others that were buffered from the effects of acidic deposition. With over 90% reductions in sulphur dioxide smelter emissions over the past 30 years and the present, many lakes in the Sudbury region are starting to show strong evidence of chemical recovery. Despite significant increases in lake water pH, there is limited evidence of biological recovery. A variety of univariate and multivariate metrics, as well as variation partitioning, were used to examine recovery on a lake-by-lake basis and on a regional scale. Our results revealed only moderate recovery of crustacean zooplankton communities despite improvements in water quality. Some lakes increased in zooplankton richness while others decreased compared to richness during peak acidification. Shifts in community composition from a damaged state toward those typical of circum-neutral lakes were observed for lakes that have chemically recovered. The lack of chemical recovery is believed to be impeding biological recovery of many lakes. Biological resistance and dispersal limitation do not appear to be hindering biological recovery. Other stressors such as the invasion by the predatory zooplankton Bythotrephes and climate change may delay biological recovery in the coming years. Future recovery of Killarney Park lakes will require further chemical recovery for biological recovery to become complete. / Thesis (Master, Biology) -- Queen's University, 2007-09-24 22:33:35.058

This study aimed to understand annual and long-term chemical and physical processes that affect the development and state of coastal lakes in the Canadian High Arctic. The first major research project studied the formation of hypersalinity in a seasonally isolated marine basin (SIMB) located near Shellabear Point, Melville Island, Northwest Territories (75'N, 113'W). To quantify the role of brine rejection from a seasonal ice pan, an annual ice-formation model was applied, which incorporated stable oxygen isotope fractionation. This model complemented seasonal sampling of ionic and isotopic composition and a full-year recording of physical lacustrine parameters. Additionally, a pilot study using radon-222 as a tracer of groundwater seepage was undertaken to quantify the brine seepage from surrounding permafrost into the hypolimnion of the SIMB. Results indicate that brine rejection from the annual formation of lake ice in a SIMB is the major driver of hypersalinity in this system, and that the current chemical constitution may have formed in less than a decade. This study contributes novel hypotheses on the chemical formation of hypersaline lakes, but also coastal meromictic lakes derived from epishelf lakes during the Holocene. The second investigation focused on the seasonal variability of limnological processes in two coastal freshwater lakes in the Canadian Arctic. East and West Lake are located at the Cape Bounty Arctic Watershed Observatory (CBAWO, 75'N, 109'W), Melville Island. From 2006 to 2009, there have been two central changes in the lake systems: 1) an enhanced ionic loading into both lakes since 2007, and 2) a significant increase in the suspended sediment concentration in the lower 15 m of West Lake in 2009. The elevated ionic concentrations are a result of increased active layer thickening during an unusually warm summer in 2007. The high turbidity in 2009 had a substantial impact on annual mixing of West Lake. The suspended sediment produced a density gradient that prevented river-generated density currents from delivering fresh oxygenated water to the bottom of the lake, and prevented thermal warming. The lack of re-oxygenation and nutrient delivery likely had a substantial impact on the benthic ecosystem in the lake. / Thesis (Master, Geography) -- Queen's University, 2010-05-24 10:26:59.208

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