title: The effects of increased constant incubation temperature and cumulative acute heat shock exposures on morphology and survival of Lake Whitefish (Coregonus clupeaformis) embryos.
abstract: Increasing incubation temperatures, caused by global climate change or thermal effluent from industrial processes, may influence embryonic development of fish. This study investigates the cumulative effects of increased incubation temperature and repeated heat shocks on developing Lake Whitefish (Coregonus clupeaformis) embryos. We studied the effects of three constant incubation temperatures (2°C, 5°C or 8°C water) and weekly, 1-h heat shocks (+3°C) on hatching time, survival and morphology of embryos, as these endpoints may be particularly susceptible to temperature changes. The constant temperatures represent the predicted magnitude of elevated water temperatures from climate change and industrial thermal plumes. Time to the pre-hatch stage decreased as constant incubation temperature increased (148d at 2°C, 92d at 5°C, 50d at 8°C), but weekly heat shocks did not affect time to hatch. Mean survival rates and embryo morphometrics were compared at specific developmental time-points (blastopore, eyed, fin flutter and pre-hatch) across all treatments. Constant incubation temperatures or +3°C heat-shock exposures did not significantly alter cumulative survival percentage (~50% cumulative survival to pre-hatch stage). Constant warm incubation temperatures did result in differences in morphology in pre-hatch stage embryos. 8°C and 5°C embryos were significantly smaller and had larger yolks than 2°C embryos, but heat-shocked embryos did not differ from their respective constant temperature treatment groups. Elevated incubation temperatures may adversely alter Lake Whitefish embryo size at hatch, but weekly 1-h heat shocks did not affect size or survival at hatch. These results suggest that intermittent bouts of warm water effluent (e.g., variable industrial emissions) are less likely to negatively affect Lake Whitefish embryonic development than warmer constant incubation temperatures that may occur due to climate change.
authors.affiliation: Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1, Canada. Electronic address: leeah4@mcmaster.ca.
authors.forename: Abigail H
authors.initials: AH
authors.lastname: Lee
authors.affiliation: Department of Biological Sciences, California State University San Marcos, 333 S. Twin Oaks Valley Rd., San Marcos, CA 92096, USA. Electronic address: johneme23@gmail.com.
authors.forename: John
authors.initials: J
authors.lastname: Eme
authors.affiliation: Department of Biological Sciences, California State University San Marcos, 333 S. Twin Oaks Valley Rd., San Marcos, CA 92096, USA. Electronic address: cmueller@csusm.edu.
authors.forename: Casey A
authors.initials: CA
authors.lastname: Mueller
authors.affiliation: Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada. Electronic address: richard.manzon@uregina.ca.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Manzon
authors.affiliation: Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada. Electronic address: chris.somers@uregina.ca.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Somers
authors.affiliation: Medical Sciences, Northern Ontario School of Medicine, Laurentian University, 935 Ramsey Lake Road, Sudbury, ON P3E 2C6, Canada; Bruce Power, Tiverton, Ontario, Canada; Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada. Electronic address: boreham@nosm.ca.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Boreham
authors.affiliation: Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1, Canada. Electronic address: joanna.wilson@mcmaster.ca.
authors.forename: Joanna Y
authors.initials: JY
authors.lastname: Wilson
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000502:physiology; D005260:Female; D018869:Heat-Shock Response; D006358:Hot Temperature; D008297:Male; D012487:Salmonidae / Q000254:growth & development / Q000502:physiology*
keywords: Climate change; Coregonus clupeaformis; Great Lakes; Heat shock; Morphology; Survival; Temperature; Thermal effluent