The effects of increased constant incubation temperature and cumulative acute heat shock exposures on morphology and survival of Lake Whitefish (Coregonus clupeaformis) embryos |
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| Institution: | 1. National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund Castle, Jægersborg Allé 1, 2920 Charlottenlund, Denmark;2. Alfred Wegener Institute, Am Handelshafen 12, 27570 Bremerhaven, Germany;3. Institute for Hydrobiology and Fisheries Science, University of Hamburg, Olbersweg 24, 22767 Hamburg, Germany;4. Fisheries and Oceans Canada, St. Andrews Biological Station, 531 Brandy Cove Road, St. Andrews, New Brunswick E5B 2L9, Canada;1. Department of Forestry and Natural Resources, Purdue University, 195 Marsteller Street, West Lafayette, IN 47907, United States;2. USGS Great Lakes Science Center, 1454 Green Road, Ann Arbor, MI 48105, United States;3. Lyles School of Civil Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, United States;4. Ontario Ministry of Natural Resources and Forestry, Suite 221e, 435 James St, Thunder Bay, ON, P7E6S8, Canada;5. Michigan Department of Natural Resources, 96 Grant St, Charlevoix, MI 49720, United States;6. Chippewa Ottawa Resource Authority, 179 W. Three Mile Road, Sault Ste. Marie, MI 49783, United States;7. Michigan Department of Natural Resources, 160 E. Fletcher, Alpena, MI 49707, United States;8. Michigan Department of Natural Resources, 484 Cherry Creek Rd, Marquette, MI 49885, United States |
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| 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 (148 d at 2 °C, 92 d at 5 °C, 50 d 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. |
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| Keywords: | Temperature Survival Morphology Great Lakes Thermal effluent Climate change Heat shock |
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