Synergistic effects of ocean acidification and copper on gamete health and fertilization potential of the Pacific oyster Magallana (Crassostrea) gigas

Abstract

Ocean acidification (OA) and metal pollution pose significant threats to marine ecosystems, particularly in coastal areas. This study investigated the synergistic effects of OA and copper toxicity on Pacific oyster (Magallana gigas) gametes. Spermatozoa and oocytes were exposed to varying pCO₂ levels and copper concentrations for 2 h. Flow cytometry was used to assess cell mortality, reactive oxygen species (ROS) production, and fertilization success. Results showed increased mortality in both sperm and oocytes with rising copper and pCO₂ levels, with sperm exhibiting higher sensitivity. ROS production in gametes displayed complex patterns, suggesting adaptive responses at lower copper concentrations and potential cell death at higher levels. Fertilization success decreased significantly at lower pH combined with higher copper concentrations (> 10 μg Cu/L). These findings demonstrate that OA exacerbates copper toxicity in M. gigas gametes through interactive effects, highlighting the need to consider multiple stressors when assessing pollutant impacts on coastal ecosystems.