Effects of fluctuating pH on shell growth and survival of juvenile eastern oysters (Crassostrea virginica)  

NSF fellow: Jessie Rivera, Florida Gulf Coast University

Mentor: Dr. Daniel Gleason

Ocean acidification negatively affects eastern oysters (Crassostrea virginica) by decreasing the pH of seawater and limiting the abundance of available carbonate needed to produce healthy shells. However, studies that report negative impacts of low pH on eastern oyster growth have usually been conducted under conditions of constant low pH. Eastern oysters generally occur in estuarine environments where pH fluctuates in tandem with semidiurnal tidal cycles, questioning the applicability of experiments conducted under constant pH. We exposed juvenile oysters to constant low (7.4), high (7.7), and fluctuating pH (7.4 - 7.7) for 28 days to gain a better understanding of how estuarine pH conditions might impact juvenile oyster shell growth and survival. While oyster weights increased similarly across pH treatments, survival was significantly reduced under low pH when compared to fluctuating and high pH conditions. These results demonstrate that the daily fluctuations in environmental pH that are tidally driven may ameliorate the negative impacts of constant low pH, especially in terms of juvenile survival. Thus, tidal fluctuations in pH should be incorporated in experimental attempts to assess the effects of current and future CO2 emissions on eastern oyster growth and survivorship.