Ocean Acidification and Ocean Warming Effects on Pacific Herring (Clupea pallasi) Early Life Stages

Abstract

Increasing green house gas emissions are expected to raise surface seawater temperatures and lead to locally intensified ocean acidity in the U.S. Pacific Northwest. Pacific herring (Clupea pallasi) are ecologically and economically important forage fish species native to this region. While the impacts of ocean acidification and ocean warming on organism physiology have been extensively studied, less is known on how concurrent climate change stressors will affect marine fish. Therefore, our study focused on the combined effects of ocean acidification and warming on Pacific herring early life history stages. Pacific herring embryos were incubated under a factorial design of two temperature (10°C or 16°C) and two pCO2 (600 μatm or 1200 μatm) treatments from fertilization until hatch (6 to 15 days depending on temperature). Elevated pCO2 was associated with a small increase in embryo mortality. Elevated temperature, as a single stressor, generated greater embryo mortality and embryo heart rates, larger yolk areas upon hatch, lower hatching success, and shorter larval lengths; compared with the same parameters measured under ambient temperature. The interaction of elevated temperature and pCO2 was associated with greater embryo heart rates and yolk areas compared to ambient conditions. This study suggests that while temperature is the primary global change stressor affecting Pacific herring embryology, interaction effects with pCO2 could introduce additional physiological challenges.

High pCO2 does not alter the thermal plasticity of developing Pacific herring embryos during a marine heatwave

“…Furthermore, this capacity means that high P CO 2 did not increase embryo mortality by limiting the amount of energy available for thermal acclimation. This finding contrasts with a recent study of Pacific herring in which exposure to ∼1200 µatm P CO 2 significantly elevated the rate of embryonic heartbeats by ∼10% at 16°C but not at 10°C ( Villalobos et al, 2020 ). Notably, embryo survival was quite low at 16°C (∼25%), so synergistic effects on metabolic rate in this species might only occur when temperatures approach or exceed upper critical limits, which were not tested in this study ( Dahlke et al, 2017 ).…”

“…This means that despite a faster growth rate, larvae from the heatwave regime were ∼10% smaller at hatch than their conspecifics reared at ambient temperatures. This is consistent with previous findings from Pacific herring ( Alderdice and Velsen, 1971 ; Dinnel et al, 2010 ; Villalobos et al, 2020 ) and fits within the broader pattern exhibited by temperate fish of an inverse relationship between hatch size and temperature ( Rombough, 1997 ). It is also assumed that temperature has proportionally equal effect on the rates of growth and yolk consumption, such that production efficiency (i.e.…”

“…High rates of organ damage were also observed in 3-week-old Atlantic herring larvae reared continuously under ∼2000 µatm P CO 2 ( Frommel et al, 2014 ). Furthermore, exposure to ∼1200 µatm P CO 2 increased the rate of mortality by 10% in Pacific herring embryos when simultaneously exposed to 16°C, but anomaly rates were not quantified in that study ( Villalobos et al, 2020 ). Thus, there is accumulating evidence that high P CO 2 may increase teratogenic effects in clupeid species by impairing normal developmental trajectories.…”

“…Clupeid offspring have been shown to be sensitive to the combined effects of elevated P CO 2 and temperature through changes in survival and development ( Franke and Clemmesen, 2011 ; Frommel et al, 2014 ; Leo et al, 2018 ; Sswat et al, 2018 ; Villalobos et al, 2020 ). Yet, the phenotypic plasticity of Pacific herring embryos exposed to combined climate stressors remains understudied, thereby constituting a serious knowledge gap for this critically important species.…”

Future Temperature and Salinity in Puget Sound, Washington State, Under CMIP6 Climate Change Scenarios

“…Increased ocean temperatures can be harmful to salmon during multiple stages of their life cycle, impacting spawning and migration, increasing mortality, and the risk of pathogens (Battin et al 2007;Beauchamp and Duffy 2011;Mauger et al 2015). Higher ocean temperatures could also lead to higher Paci c herring embryo mortality (Villalobos et al 2020). Furthermore, the loss in snowpack will reduce salmon spawning area in rivers in the Puget Sound watershed, leading to an expected decline in salmon population (Battin et al 2007).…”