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The role of the bottom sediments in the eutrophication of Georgetown Lake, Montana
| Content Provider | Semantic Scholar |
|---|---|
| Author | Garrison, Paul J. |
| Copyright Year | 1976 |
| Abstract | Georgetown Lake is a relatively small reservoir located in southwestern Montana. It receives much recreational use all year round being the most heavily fished lake in the state for its size. The present study was part of a larger limnological project to evaluate the limnology of the reservoir. This particular study was undertaken to determine the extent to which the sediments may provide nutrients to the overlying waters, Suring the ice free period Georgetown Lake did not exhibit chemical stratification. During the ice cover period at the deep water station oxygen declined until the bottom waters became anaerobic and the water column became chemically stratified. At this time certain elements such as ortho-phosphorous, ammonia, iron, silica, bicarbonate, etc. were released into the bottom waters from the sediments. With the advant of ice-out and the reintroduction of oxygen, the stratification disappeared and iron and manganese precipitated causing some phosphorus to be precipitated. As a result of turbulent mixing orthophosphorus and iron appeared to be suspended in the bottom waters during the summer. In the sediments iron oxides, aluminum oxides, exchangeable manganese, exchangeable zinc, inorganic phosphorus, and exchangeable ammonia decreased during the ice cover period but increased at ice out. Only exchangeable manganese followed this trend at the shallower station. At the deep water station iron oxides and aluminum oxides appeared to be associated with the same particles. At the shallower station where macrophytes were present, aluminum oxides and iron oxides were associated with different particles, probably because of iron accumulation by the plants. The proportion of the initial volatile solids attributable to organic carbon varied with the season because of the rate of benthic decomposition. During the ice cover period organic phosphorus regulated the total phosphorus because of detrital deposition the previous autumn. During the ice free period inorganic phosphorus determined total phosphorus trends because of macrophytic uptake. There was a potential for much phosphorus to be released into the water under the right conditions as exchangeable phosphorus makes up 14 to 25$ of the sediment inorganic phosphorus. Although organic nitrogen makes up the majority of the total nitrogen, it was less important than reported in the literature. This was a result of the shallow depth of the lake which makes the bottom environment more conducive to microbial mineralization. This is supported by the C:N which was 31:1. Because of the deep-water withdrawl of the dam, much nitrogen and phosphorus was discharged during anaerobic conditions in the bottom waters. This is indicated by the C:N:P of 469:31:1. This results in an annual loss of both total nitrogen and total phosphorus from the lacustrine ecosystem. STATEMENT OF PERMISSION TO COPY In presenting this thesis.in partial fulfillment of the requirements for an advanced degree at Montana State University, I agree that the Library shall make it freely available for inspection. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by my major professor, or, in his absence, by the Director of Libraries. It is understood that any copying or publication of this thesis for financial gain shall not be allowed without my written permission. |
| Starting Page | 1 |
| Ending Page | 134 |
| Page Count | 134 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://scholarworks.montana.edu/xmlui/bitstream/handle/1/3789/31762001550878.pdf;jsessionid=8D4CD70E268ECB11BFF7BA289161B8A0?sequence=1 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
