Lake and round whitefish are cold-adapted freshwater species with similar life
histories and spawning behaviours. There have been several studies on the embryonic
development of both species (particularly for lake whitefish), most utilizing constant
temperatures. However, temperatures fluctuate in the field due to natural (e.g. seasonal
changes) and anthropogenic (e.g. water discharged from once-through cooling processes)
effects. Releases from once-through cooling processes may contain low levels of
chemicals (e.g. morpholine) and radiation (e.g. tritium). This thesis examined and
compared the impacts of thermal, morpholine, and radiation stressors on lake and round
whitefish embryogenesis.
To examine the effects of fluctuating incubation temperatures, lake and round
whitefish were reared at constant temperatures, with seasonal temperature
declines/inclines, transient temperature spikes, or seasonal temperature changes combined
with temperature spikes. Round whitefish embryos had significantly higher mortality
when reared at 8°C compared to lake whitefish, and seasonal temperature changes
impacted development rate, growth, and hatch dynamics for both species. Temperature
spikes had relatively little effect on development.
The effects on embryonic development of chronic morpholine and low-dose
radiation exposures were examined in round whitefish to compare with existing data in
lake whitefish. Round whitefish embryos were more impacted by morpholine than lake
whitefish (larger effects on growth and mortality at relatively lower concentrations) and
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less impacted by low-dose radiation (little effect on growth or hatch dynamics). Post
hatch, round whitefish embryos reared at 8°C, with rapid seasonal inclines, or with 500
mg L-1 morpholine had elevated mortality. All irradiated embryos had decreased mortality
post-hatch compared to non-irradiated embryos. Thus, embryonic exposure to all stressors
examined appears to alter post-hatch survival.
This thesis better defines the effects of fluctuating incubation temperatures,
chronic morpholine, and chronic radiation exposures on the embryonic development of
lake and round whitefish. It also suggests that embryonic incubation conditions are
important beyond hatching. / Thesis / Master of Science (MSc) / Lake and round whitefish are cold-adapted freshwater species. Both species
play important ecological roles, with lake whitefish generally perceived as more
economically and culturally important. Many studies have detailed lake whitefish
embryonic development under constant stressors (e.g. temperature) but there are
relatively few studies on round whitefish embryonic development. Both species
experience seasonal temperature fluctuations in nature and may experience
additional anthropogenic temperature, chemical, and radiation stress due to
discharge from once-through cooling processes at thermal power plants, which may
contain low levels of morpholine and radiation. Our study suggests that round
whitefish embryos are more sensitive to elevated temperature and morpholine
levels, but less impacted by chronic low-dose irradiation relative to lake whitefish
embryos. The growth and development of both species are significantly affected by
seasonal temperature changes.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/20513 |
| Date | January 2016 |
| Creators | Lim, Michael |
| Contributors | Wilson, Joanna, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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