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
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/5953 |
| Date | 04 August 2010 |
| Creators | HAWRYSHYN, HAWRYSHYN, |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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