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The utility of sedimentary diatoms as a measure of historical lake ph

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Show simple item record Dixit, Sushil Sharan. en_US 2009-07-09T18:54:32Z 2009-07-09T18:54:32Z 1983-07-09T18:54:32Z
dc.description.abstract As a result of increased acid precipitation, the pH of a large number of Canadian Shield lakes has been falling. Prior to this study there was no documentation available to explain the history of lake acidification for the Algoma area lakes. In order to obtain this information the diatom inferred pH technique was developed in this study. During two field seasons, July 1981 and July 1982, short sediment cores (circa 25-30 cm) were collected from 28 study lakes located north of Lake Superior, District Algoma, Ontario. The surface sediment diatoms (0-1 cm) from each of these lakes were carefully identified, enumerated, and classified in terms of their pH indicator status. The surface sediment diatom analysis indicated that lake pH is one of the most important factors affecting the species composition and relative abundance of diatom populations. Thus diatom assemblages can be sensitive indicators of lake acidification. When Nygaard's index alpha was plotted against observed lake pH, a statistically significant relationship resulted (r=-0.89; p=<O.OI). The index alpha regression equation was used to construct the pH histories of 4 lakes (lakes X4, CS, U3, and WI). The repeatability of this technique was confirmed by comparing two downcore paleo-pH profiles of Lake WI. These two paleo-pH profiles represented almost identical paleo-pH patterns for Lake WI. The paleo-pH study of Lake X4 revealed that the lake has been rather acidic (pH <5.6) for the last 200 years. It appears that the recent increase in acid precipitation 3 over the last 30 years has not altered the water pH compared to the lake's pH history. However, the paleo-pH study of another acidic lake (Lake CS) indicated that its pH has significantl}* dropped over the last 30 years . During this time the Lake CS pH has dropped almost 2 pH units (7.1 to 5.2). The other two lakes studied for downcore pH were circumneutral in nature . One of these lakes (Lake U3) displayed a relatively stable pH history while the other lake (Lake WI) displayed significant pH fluctuations over post-Ambrosia time. The variable pH history of Lake WI was probably associated with the Algoma sintering plant plume and forest fires. A significant relationship between surface sediment diatoms and observed lake pH and secondly a statistically significant relationship between index alpha and observed pH suggested that diatoms are one of the best indicators of lake pH. Thus diatom inferred pH technique has great potential in explaining the rate of lake acidification. en_US
dc.language.iso eng en_US
dc.publisher Brock University en_US
dc.subject Hydrogen-ion concentration. en_US
dc.subject Lake sediments--Ontario--Algoma (District) en_US
dc.subject Lakes--Ontario--Algoma (District) en_US
dc.subject Diatoms. en_US
dc.subject Water--Pollution--Ontario--Algoma (District) en_US
dc.title The utility of sedimentary diatoms as a measure of historical lake ph en_US
dc.type Electronic Thesis or Dissertation en_US M.Sc. Biological Sciences en_US Masters en_US
dc.contributor.department Department of Biological Sciences en_US Faculty of Mathematics and Science en_US

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