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 twopCO2(600 μatm or 1200 μatm) treatments from fertilization until hatch (6 to 15 days depending on temperature). ElevatedpCO2was 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 andpCO2was 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 withpCO2could introduce additional physiological challenges.
Highlights
Pacific herring are key prey for ecologically and commercially important finfish, sea birds and marine mammals in the U.S Pacific Northwest (PNW) (Fresh et al, 1981), and their eggs are a lipid-rich resource for many marine invertebrate and vertebrate foragers (Penttila, 2007)
The influence that these climate stressors will have on marine fish are beginning to be understood (e.g., Munday et al, 2009a; Hurst et al, 2013; Sswat et al, 2018), but to date little is known about the effects of elevated pCO2 on Pacific herring (Clupea pallasii), especially the combined effects of temperature and pCO2 on their early life history stages
Given that the mean temperature measured at Cherry Point during spawning season is already within 1 degree of the high temperature investigated here (DNR), and that further increases of between 1.5 and 4◦C can be expected (Khangaonkar et al, 2018), temperature stress may become critical for larval herring at Cherry Point and in the Salish Sea
Summary
Pacific herring are key prey for ecologically and commercially important finfish, sea birds and marine mammals in the U.S Pacific Northwest (PNW) (Fresh et al, 1981), and their eggs are a lipid-rich resource for many marine invertebrate and vertebrate foragers (Penttila, 2007). Attempts to gain an understanding about the effects of higher temperatures and elevated pCO2 on coastal marine species have been under investigation for some time (Doney et al, 2012; Harvey et al, 2013), and the effects of these climate variables are context and species-dependent (Harvey et al, 2013) The influence that these climate stressors will have on marine fish are beginning to be understood (e.g., Munday et al, 2009a; Hurst et al, 2013; Sswat et al, 2018), but to date little is known about the effects of elevated pCO2 on Pacific herring (Clupea pallasii), especially the combined effects of temperature and pCO2 on their early life history stages. Stressors such as climate change and habitat loss can have strong effects on early life stages, and loss of fitness or increased mortality in these stages can have serious impacts on population trends
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