Investigating Long-term Environmental Trends in Central Ontario Lakes Impacted by Cyanobacterial Blooms
Loading...
Authors
Favot, Liz
Date
Type
thesis
Language
eng
Keyword
blue-green algae , paleolimnology , climate change , aquatic ecology
Alternative Title
Abstract
Cyanobacterial blooms degrade water quality by increasing turbidity, causing taste and
odour problems, depleting deep-water oxygen concentrations, and producing toxins – all of
which can alter aquatic food webs, and depreciate the social and economic value of waterbodies.
A common driver of blooms is nutrient enrichment; however, climate-related factors, like surface
water temperature, intensity and duration of thermal stratification, precipitation, and wind speed,
are also important predictors. Consequently, climate change is expected to increase the spatial
extent, severity, frequency, and duration of cyanobacterial blooms. Reports of blooms have
increased in recent decades in Canadian lakes, but a lack of long-term monitoring hinders
attempts to identify the causes. This thesis examined environmental indicators preserved in lake
sediment cores to reveal multi-century trends in water quality and investigate drivers for these
recent cyanobacterial blooms. In a remote oligotrophic lake, marked increases in cyanobacterial
microfossils in surficial sediments and an increasing trend in primary production since ~1930
CE, in the absence of nutrient enrichment, suggest a climatic driver for recent unprecedented
Dolichospermum blooms. In three rural northeastern Ontario lakes, eutrophication in ~1930 CE
potentially associated with forest removal and settlement was tracked in diatom assemblages in
two of the lakes. However, bloom occurrence in these lakes over a half-century later was
associated with distinct diatom species shifts, indicative of enhanced thermal stratification. In
Callander Bay, Lake Nipissing, a climate-mediated shift from polymictic conditions to sustained
summertime stratification, and increased bottom water anoxia and internal nutrient loading since
~2000 CE, are linked to recent cyanobacterial prevalence. At eight additional sites across Lake
Nipissing, diatoms in modern and pre-industrial era sediments revealed strikingly similar
assemblage shifts indicative of lake-wide enhanced thermal stratification, indicating more favourable conditions for blooms. Estimates of baseline nutrient and hypolimnetic oxygen
concentrations derived in this study can be used to guide management targets. Collectively,
increasing primary production tracked over the last several decades (without parallel increases in
nutrient enrichment) across all study lakes has likely occurred due to regional warming and a
longer ice-free growing season, and invokes climate change as an important driver of
cyanobacterial blooms in temperate lakes.
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.
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.