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The aim of this literature study is to compare and discuss different fields of paleolimnology, with a focus on three main research areas – eutrophication, acidification, and climate change. Pioneering work and the development of paleolimnological methods around these three areas were reviewed and synthesized. Paleolimnology started out as limnology and paleoecology, but has evolved tremendously over the past decades. Early paleolimnological studies focused on lake ontogeny and mechanics in the catchment such as weathering. The focus eventually shifted to nutrient loadings during the 1960s – 1970s as the debate on human induced eutrophication emerged. The important question to answer was which nutrient was the limiting factor in eutrophication. Acidification was the next topic of investigation during the 1980s – 1990s, and paleolimnology developed methods to infer past pH change based on chironomids and diatom fossils preserved in lake sediment. This research resulted in calibration sets and proxies which can be used to reconstruct past conditions. The paleolimnological community eventually shifted focus in the late 1990s to climate change and began to use lake sediment to reconstruct past climatic trends using multiproxy studies such as diatoms, chironomids and geochemistry. Varved lake sediment offered a much needed terrestrial high resolution option to the ice core records. History plays a fundamental role in all environmental issues and paleolimnology has the ability to provide historical records of past environmental conditions. Paleolimnology will most likely play a key role in management and restoration in the future. As technology and training sets develop, fast and cheap ways to interpret sediment proxies will emerge and maybe even fully automated identification of proxies.

Freshwater systems in Canada are affected by a multitude of environmental stressors, including cultural eutrophication, introduction of non‐native species, and climate change. Multiple stressors can interact in unpredictable ways and generate novel ecological scenarios, thus creating challenges for lake management. Lake Simcoe is an example of an aquatic system impacted by multiple stressors, facing management challenges of deteriorating water quality and coldwater fisheries. In order to better understand stressor interactions and pre‐disturbance lake conditions, a long‐term perspective is necessary. Therefore, this study used paleolimnological techniques to assess changes in the water quality of Lake Simcoe over the past ca. 200 years. Sedimentary diatom assemblages were analyzed in 210Pb‐dated cores from five sites across the lake. Diatom assemblages recorded several pronounced and synchronous shifts over the last ca. 200 years. Modest lake‐wide shifts in diatom community composition occurred in the late‐1800’s and early‐1900’s, suggesting that early cultural disturbances, such as land clearance and canal construction, had relatively minor impacts on Lake Simcoe. However, starting in the 1930’s, agricultural and urban development intensified, as indicated by substantial increases in eutrophic taxa. The most pronounced lake‐wide shift in diatom assemblages occurred in the mid‐to‐late 1900’s, the taxonomic nature and timing of which strongly suggest a response to regional climate warming. Moreover, diatom compositional trends at all sites were significantly correlated with instrumental records of regional temperature and lake ice the last ca. 100 years. An additional and marked lake‐wide shift in diatom assemblages occurred in the mid-1990’s, coinciding with the invasion of dreissenid mussels. The combination of stressors acting concurrently on Lake Simcoe, as well as the lake’s distinct water chemistry and size, make it challenging to reconstruct single limnological variables (such as, total phosphorus) in this system. Nevertheless, overall patterns of diatom compositional changes from the five sites revealed the largest shifts occurred in the post‐1950 sediments and that change in lake‐water total phosphorus concentrations played a minor role. Our results imply that substantial changes in climate have amplified the effects of multiple stressors in this complex system. / Thesis (Master, Biology) -- Queen's University, 2010-08-04 12:03:42.267

Optimization of the culture conditions for the biomass production of the alga Phaeodactylum tricornutum was investigated in relation to chlorophyllase activity. To obtain the highest total chlorophyllase activity, the biomass of P. tricornutum was harvested after a period of 7 days of incubation during which the incubation temperature was maintained at 18°C for 18 h during the day and 10°C for 6 h during the night. During culture incubation, illumination was provided by fluorescent lamps projecting an incident intensity of 330 mumol/m2.s and the pH of the culture was maintained at 8.4, adjusted by a stream flow of CO 2. The hydrolytic activity of a partially purified chlorophyllase extract, obtained from the fresh biomass of P. tricornutum, was investigated in an aqueous/miscible organic solvent system containing refined bleached deodorized (RBD) canola oil, and chlorophyll or pheophytin as substrate. The effect of a wide range of oil contents, chlorophyll and pheophytin concentrations, acetone concentrations, incubation temperatures and agitation speeds on the enzyme activity was studied. The optimum reaction conditions for chlorophyllase biocatalysis were determined to consist of 20% oil, 10% acetone and a 200 rpm agitation speed with optimum temperatures and substrate concentrations of 35°C and 12.6 muM for chlorophyll, and 30°C and 9.3 muM for pheophytin. The presence of RBD canola oil showed an inhibitory effect on chlorophyllase activity whereas acetone acted as an activator at low concentrations and an inhibitor at higher ones. Moreover, chlorophyllase showed a limited affinity towards pheophytin as substrate compared to that obtained for chlorophyll. Selected samples of crude commercial canola oil were analyzed for their green pigment content using high-performance liquid chromatography and chlorophyllase biocatalysis was investigated on eight varieties of crude commercial canola oil. The chlorophyllase activity was lower in th

Graduation date: 1982

During the recessional flow period of 2004, benthic diatoms were sampled from four catchments in the tropics of the Northern Territory of Australia. Each of the catchments showed evidence of acid mine drainage. Diatoms were used in conjunction with physical and chemical water parameters to provide a biomonitoring approach with the ultimate goal to assess the water quality of the mine impacted catchments. A total of 267 species of diatoms from 45 genera were recorded from 50 sites in the Northern Territory. One of the primary aims of this study was to assess diatom classification techniques, morphological and genetic, for the accurate identification of the morphologically variable taxon, Nitzschia palea. A second primary aim was to determine the degree to which diatom taxa and community structures can be effectively used as biological indicators and monitors of heavy metal pollution in tropical aquatic environments. To address the lack of diatom floristic studies from the Northern Territory, an iconograph of the most abundant taxa was created. Forty eight Nitzschia palea-like cells were cultured and then grouped by hierarchical cluster analysis (Ward’s method). The reliability of the groups was tested with discriminant analysis. The morphological groups were compared to the phylogenetic grouping of 20 of the cultures which were each genetically sequenced using the nuclear-encoded small subunit rDNA. For monitoring studies, multivariate statistical techniques were used to produce models to infer environmental variables from diatom distributions. The three datasets used varied in terms of the level of taxonomic identification and the inclusion of bioavailable or total metal concentrations. The program AquaRisk was employed to determine the bioavailable concentrations of the heavy metals. Each dataset was related to water quality parameters using canonical correspondence analysis. The Simpson’s index and the Shannon-Wiener diversity index were statistically related, together with species richness, to the variables pH and copper through bivariate regression analysis. To determine the usefulness of individual diatom taxa as indicators, species were selected based on their occurrence, weighted average optima and tolerance values, and species response curves. Additionally, teratogenic frustules were statistically correlated with environmental variables by bivariate and linear regression. Although the Nitzschia palea-like cultures displayed morphological variation, which could be used separate the cultures into five distinct groups, the cultures were not found to be genetically variable. However, one new species, Nitzschia sp. 39, was defined genetically and described morphologically. As with other analyses of mine impacts, canonical correspondence analysis identified pH and aluminium as the principal environmental factors structuring the diatom communities. The calibration set models generated to infer pH and heavy metals had high predicative capabilities. Overall, the species dataset, rather than the datasets utilising genus level identification or bioavailable metal fractions, provided the statistically strongest results. Monitoring using diversity indices was less successful for indicating pollution. Contrary to findings from other studies, species richness tended to be higher in polluted waters than control sites. Unlike other studies of acidic environments, the species Chamaepinnularia mediocris, Naviculadicta subtilissima, Nitzschia vasta and Pinnularia schoenfelderi were found to be the best indicators. Nitzschia vasta was the only teratogenic diatom within the dataset. However, as with other analyses, the relationship between teratogenic valves and mine impact was not significant. This study demonstrates the continued need for research in the tropics in order to better understand biological responses and enable study comparisons. Although at least one new xii species was identified, the genetic research indicated that taxonomic texts produced for northern hemisphere regions can be applied to tropical diatom taxa as long as the risk of taxonomic force fitting is avoided. Additionally, the benefit of diatoms as biological monitors varies depending on the method utilised. In these highly impacted systems, transfer functions produced the strongest results. In contrast, it is evident that the abundance and distribution of teratological forms of diatoms are poor indicators of impact. Further work culturing diatoms and combining this technique with ecotoxicological work will help verify autecologies of taxa and their responses to co-varying pollutants. This will strengthen use of diatom taxa as indicator species. Continued monitoring of these sites can add much to our ecological understanding of these highly impacted systems which, in turn, will lead to better management of the systems for both sustainable resource development and conservation. / Thesis (Ph.D.) -- University of Adelaide, School of Social Sciences, 2008

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (M.S.)--Ohio University, August, 2006. / Title from PDF t.p. Includes bibliographical references.

Thesis (M.S.)--Duquesne University, 2007. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references (p. 67-70) and index.

Thesis (M.S.)--California Institute of Technology, 1931. / Includes bibliographical references (leaves 60-61).