Differential sensitivity to warming and hypoxia during development and long-term effects of developmental exposure in early life stage Chinook salmon

Annelise M Del Rio; Gabriella N Mukai; Benjamin T Martin; Rachel C Johnson; Nann A Fangue; Joshua A Israel; Anne E Todgham

doi:10.1093/conphys/coab054

Differential sensitivity to warming and hypoxia during development and long-term effects of developmental exposure in early life stage Chinook salmon

Conserv Physiol. 2021 Jul 8;9(1):coab054. doi: 10.1093/conphys/coab054. eCollection 2021.

Authors

Annelise M Del Rio¹, Gabriella N Mukai^{1

2}, Benjamin T Martin^{3

4

5}, Rachel C Johnson^{1

3

4}, Nann A Fangue⁶, Joshua A Israel⁷, Anne E Todgham¹

Affiliations

¹ Department of Animal Science, University of California Davis, Davis, CA 95616, USA.
² Department of Biology, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA.
³ University of California Santa Cruz, Cooperative Institute for Marine Ecosystems and Climate (CIMEC), Santa Cruz, CA 95064, USA.
⁴ Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 110 Shaffer Road, Santa Cruz, CA 95060, USA.
⁵ Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, 1098 XH Amsterdam, the Netherlands.
⁶ Department of Wildlife, Fish, and Conservation Biology, University of California Davis, Davis, CA 95616, USA.
⁷ Bay-Delta Office, U.S. Bureau of Reclamation, Sacramento, CA 95825, USA.

Abstract

Warming and hypoxia are two stressors commonly found within natural salmon redds that are likely to co-occur. Warming and hypoxia can interact physiologically, but their combined effects during fish development remain poorly studied, particularly stage-specific effects and potential carry-over effects. To test the impacts of warm water temperature and hypoxia as individual and combined developmental stressors, late fall-run Chinook salmon embryos were reared in 10 treatments from fertilization through hatching with two temperatures [10°C (ambient) and 14°C (warm)], two dissolved oxygen saturation levels [normoxia (100% air saturation, 10.4-11.4 mg O₂/l) and hypoxia (50% saturation, 5.5 mg O₂/l)] and three exposure times (early [eyed stage], late [silver-eyed stage] and chronic [fertilization through hatching]). After hatching, all treatments were transferred to control conditions (10°C and 100% air saturation) through the fry stage. To study stage-specific effects of stressor exposure we measured routine metabolic rate (RMR) at two embryonic stages, hatching success and growth. To evaluate carry-over effects, where conditions during one life stage influence performance in a later stage, RMR of all treatments was measured in control conditions at two post-hatch stages and acute stress tolerance was measured at the fry stage. We found evidence of stage-specific effects of both stressors during exposure and carry-over effects on physiological performance. Both individual stressors affected RMR, growth and developmental rate while multiple stressors late in development reduced hatching success. RMR post-hatch showed persistent effects of embryonic stressor exposure that may underlie differences observed in developmental timing and acute stress tolerance. The responses to stressors that varied by stage during development suggest that stage-specific management efforts could support salmon embryo survival. The persistent carry-over effects also indicate that considering sub-lethal effects of developmental stressor exposure may be important to understanding how climate change influences the performance of salmon across life stages.

Keywords: Carry-over effects; developmental windows; hypoxia; multiple stressors.