Oyster reproduction is compromised by acidification experienced seasonally in coastal regions

Abstract

Atmospheric carbon dioxide concentrations have been rising during the past century, leading to ocean acidification (OA). Coastal and estuarine habitats experience annual pH variability that vastly exceeds the magnitude of long-term projections in open ocean regions. Eastern oyster (Crassostrea virginica) reproduction season coincides with periods of low pH occurrence in estuaries, thus we investigated effects of moderate (pH 7.5, pCO2 2260 µatm) and severe OA (pH 7.1, pCO2 5584 µatm; and 6.7, pCO2 18480 µatm) on oyster gametogenesis, fertilization, and early larval development successes. Exposure at severe OA during gametogenesis caused disruption in oyster reproduction. Oogenesis appeared to be more sensitive compared to spermatogenesis. However, Eastern oyster reproduction was resilient to moderate OA projected for the near-future. In the context of projected climate change exacerbating seasonal acidification, OA of coastal habitats could represent a significant bottleneck for oyster reproduction which may have profound negative implications for coastal ecosystems reliant on this keystone species.

Carryover effects of temperature and pCO2 across multiple Olympia oyster populations

“…In contrast to prior studies, temperature and pCO 2 did not impact O. lurida sex ratios, whereas in high pCO 2 , C. virginica skewed male (Boulais et al. ) and S. glomerata skewed female (Parker et al. ).…”

“…() found S. glomerata gametogenesis to slow in 856 μatm (pH 7.91), and Boulais et al. () found normal rates at 2,260 μatm (pH 7.5), delay at 5,584 μatm (pH 7.1), and full inhibition at 18,480 μatm (pH 6.9) in C. virginica . Together, these studies indicate that high pCO 2 slows the rate of gametogenesis, but the level at which pCO 2 affects gametogenesis appears species‐specific, and likely reflective of variable physiological mechanisms and reproductive strategies.…”

“…Similar impacts on gametogenesis during exposure were observed in the Sydney rock (S. glomerata) and Eastern (C. virginica) oysters, but with varying pCO 2 thresholds. Parker et al (2018) found S. glomerata gametogenesis to slow in 856 latm (pH 7.91), and Boulais et al (2017) found normal rates at 2,260 latm (pH 7.5), delay at 5,584 latm (pH 7.1), and full inhibition at 18,480 latm (pH 6.9) in C. virginica. Together, these studies indicate FIG.…”

“…The few studies to date show that high pCO 2 delays gametogenesis in the oysters Crassostrea virginica and S. glomerata (Boulais et al. , Parker et al. ), but both studies exposed oysters during gametogenesis.…”

“…The impacts of winter acidification on estuarine bivalve reproduction are less predictable. The few studies to date show that high pCO 2 delays gametogenesis in the oysters Crassostrea virginica and S. glomerata (Boulais et al 2017, Parker et al 2018), but both studies exposed oysters during gametogenesis. Acidification during the winter months could increase energetic requirements (Sokolova et al 2012), and deplete glycogen reserves that are later utilized for gametogenesis in the spring (Mathieu and Lubet 1993), but this hypothesis has yet to be tested.…”