Recent studies within the past decade or so have shown the importance of algae in geomorphic and hydrologic processes of lotic systems. However, the ecohydraulic role of algae in bedrock systems has largely been ignored. In addition, the utility of algae as indicators of channel dynamics have often been assumed by geomorphologists, but relatively few studies have examined this relationship. The purpose of this study was to determine whether algae, specifically diatoms, are useful indicators of channel geomorphological dynamics, and to examine if distinct habitats or biotopes typical in fluviokarst and bedrock systems provide unique habitat space for diatoms, and to address the potential ecohydraulic implications. The investigation was performed in a 100 m reach of Shawnee Run, a limestone, fluviokarst tributary to the Kentucky River in Mercer County, KY. The results of the study showed that periphyton are not useful indicators of channel dynamics, and that biotopes and other distinct habitats, including riffles, bedforms, and fine sediment, do not provide unique habitat in terms of diatom community composition.

The vast majority of Adirondack lakes have been impacted since pre-industrial time through either regional (e.g. acidification) or local (e.g. fish stocking, liming, seepage of road salt, cultural eutrophication) environmental disturbances. Inferring changes related to climate are difficult due to the possible complexities associated with multiple stressors. Thirty minimally-disturbed ‘reference’ lakes were identified from a database of 1469 lakes using the following selection criteria: <5% shoreline development; a circumneutral pH; and no records of introduction of non-native piscivores (protecting against eutrophication, chronic lake acidification and modifications of trophic structure, respectively). As such, these ‘reference’ lakes may be useful for isolating the effects of regional changes, including climate warming, from other anthropogenic influences. A ‘top-bottom’ paleolimnological analysis of diatom assemblages was undertaken to identify changes since pre-industrial times. The uppermost sediment layer was used to represent present-day diatom assemblages, and a sediment sample from a depth of 20cm was used to represent pre-industrial conditions. Discostella stelligera, a planktonic diatom taxon, is presently the dominant species in 50% of the lakes, and showed the greatest change. D. stelligera increased by >10% in 11 of the 30 study lakes. The measured present-day chemical and physical limnological variables in the study lakes could not predict changes in the abundance of D. stelligera, suggesting that unmeasured variables, such as decreased ice cover, and changes in mixing and stratification patterns, are likely driving the observed changes in diatom assemblages. Heavily silicified tychoplanktonic Aulacoseira species declined by an average of 8.3% across the dataset. In three of the relatively deep lakes with higher concentrations of phosphorus, another planktonic diatom, A. formosa, was found to increase in abundance. Additionally, some lakes that were dominated by a high proportion of benthic taxa experienced increases in the relative abundance of benthic taxa over time. Observed changes in the relative abundances since pre-industrial times are significantly higher than the variation between replicate cores, and between two ‘pre-industrial’ sediment intervals. Further studies on the timing of changes in diatom assemblages are necessary to confirm that such changes are consistent with recent changes in climate in the Adirondacks. / Thesis (Master, Biology) -- Queen's University, 2014-05-29 21:33:42.24

Low dissolved zinc concentrations in marine waters can limit growth and productivity of phytoplankton. as Zn is a required component of critical enzymes such as carbonic anhydrase. This thesis examined the effects of Zn availability on growth rates. cell morphology, elemental composition and ratios, and incorporation rates of macronutrients in the coastal diatom Skeletonema costatum and the oceanic diatom Thalassiosira oceanica. Under Zn limitation. S. costatum exhibited a decrease in maximum growth rate (60%), chlorophyll content (20%) and an increase in the surface to volume (S/V) ratio (80%) compared to Zn-replete cells. In S. costatum elemental quotas showed a decrease in silicon content (20%) and a significant increase in carbon content (52%) and phosphorus content (55%). Moreover. silicon content per surface area significantly decreased by 50% under Zn limitation. Elemental ratios showed significant differences only for Si:C and Si:N between Zn-replete and Zn limiting conditions. The elemental stoichiometry of S. costatum was 82C : 9N : 5Si : 1P under Zn-limiting conditions compare to 84C : 12N : 9Si : 1 P under Zn-replenishment. In T oceanica. Zn limitation was also responsible for a decrease in maximum growth rate (60%) and chlorophyll content (20%) compared to Zn-replete cells, but Zn limitation did not affect the S/V ratio. Elemental quotas and ratios in T. oceanica did not exhibit significant differences under Zn limitation. However. nitrogen. silicon and phosphorus content showed a 20% increasing trend in Zn-limited cells. Elemental quotas for T. oceanica were 51C : 6N : 2Si : 1P under Zn-limitation and 71C : 6N : 2Si : 1P under Zn-replenishment. These laboratory experiments suggest that Zn availability in the oceans can affect the stoichiometry of nutrient uptake and the structure of phytoplankton assemblages. especially in coastal environments.

Rapidly changing climates in northern Canada make the western Hudson Bay region an area of high importance for paleoenvironmental studies. Long-term changes in assemblages of diatoms (microscopic algae) were analyzed from lake sediment cores from Baker Lake, Nunavut, and Lake AT01, northern Ontario, to track responses to past environmental changes. Diatom assemblages dating to 6700 years ago in AT01 were initially characterized by cold- tolerant Fragilarioid assemblages, but shifted to an assemblage dominated by large benthic species and Cymbella diluviana consistent with the timing of the Holocene Thermal Maximum after 6300 years BP. A possible drainage event in Lake AT01 may have added significant hydrologic control on the diatom assemblages. The post-industrial period is marked by the largest compositional shifts in both records. Assemblages during the 20th century are indicative of reduced ice cover and enhanced thermal stratification linked to a climate regime shift noted in Hudson Bay since the mid-1990’s.

Rapidly changing climates in northern Canada make the western Hudson Bay region an area of high importance for paleoenvironmental studies. Long-term changes in assemblages of diatoms (microscopic algae) were analyzed from lake sediment cores from Baker Lake, Nunavut, and Lake AT01, northern Ontario, to track responses to past environmental changes. Diatom assemblages dating to 6700 years ago in AT01 were initially characterized by cold- tolerant Fragilarioid assemblages, but shifted to an assemblage dominated by large benthic species and Cymbella diluviana consistent with the timing of the Holocene Thermal Maximum after 6300 years BP. A possible drainage event in Lake AT01 may have added significant hydrologic control on the diatom assemblages. The post-industrial period is marked by the largest compositional shifts in both records. Assemblages during the 20th century are indicative of reduced ice cover and enhanced thermal stratification linked to a climate regime shift noted in Hudson Bay since the mid-1990’s.

No description available.

Thesis (M.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 80-95). Also available in electronic format on the Internet.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 67-73). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 171-185). Also available on the World Wide Web.

Thesis--Paris VI, 1977. / Includes bibliographical references (t. 1, p. 321-346).