Assessing Lake Ecosystem Recovery from Acidification and Responses to Emerging Environmental Stressors: a Paleolimnological Perspective
Loading...
Authors
Cheng, Michelle
Date
Type
thesis
Language
eng
Keyword
Paleolimnology , Diatom , Acidification , Sudbury , Biological Recovery
Alternative Title
Abstract
Mining and smelting activities have heavily affected the Sudbury (Ontario, Canada) region since the late-19th century, leading to acidification and metal contamination in many ecosystems. Regulations on restricting acidic emissions were enacted in the 1970s, after which many Sudbury-region lakes recorded increasing pH and decreasing metal concentrations. Meanwhile, other emerging stressors have likely affected these lakes over the past few decades. Here, I revisit lakes in the Sudbury region, half a century after the application of remedial efforts, to assess lake ecosystem recovery from acidification and their responses to newly emerging environmental stressors. First, a canonical correspondence analysis is used to assess the relationships between surface-sediment diatom assemblage structure and environmental variables for 80 lakes. Lakewater pH remains the strongest environmental variable shaping diatom species distributions, and so is used to construct a robust inference model (R2boot = 0.73; RMSEP = 0.32). Additionally, by assessing ecological changes experienced by a subset of these lakes (n = 33, in common with Dixit et al. 2002) over the past few decades, two major trends are identified: an overall increase in diatom-inferred pH and a rise in the relative abundance of planktonic taxa. Further, down-core analyses in dated sediment cores are conducted to assess detailed ecological changes for three historically acidified lakes and two reference systems over the past ~200 years. Despite recording marked chemical recovery, the acidified lakes showed minimal or no evidence of biological recovery, with recent diatom assemblages markedly different from pre-disturbance assemblages, likely due to the legacy effects of acidification and climate warming. Biological recovery is lagging chemical recovery in acidified systems half a century after the reduction of acid deposition, and a return to pre-disturbance biological assemblages may never be achieved due to emerging environmental stressors, especially recently accelerated climate warming.
Description
Citation
Publisher
License
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
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.
Attribution-NonCommercial-NoDerivs 3.0 United States
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
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.
Attribution-NonCommercial-NoDerivs 3.0 United States