Investigating the effects of ocean acidification on shellfish

Mechanisms and physiological costs of shellfish adaptation to Ocean Acidification

Schematic of the chemical reactions that result in ocean acidification (Source: NOAA)

Increased carbon dioxide emissions, in part as a result of recent anthropogenic activities, have led to a reduction of global ocean pH and thus a more acidic ocean. This process, called ocean acidification (OA), is predicted to accelerate through the end of the century resulting in a decrease in pH from 8.2 to 7.8 by the year 2100. This magnitude of change is unprecedented in the past one million years. The change in ocean chemistry associated with OA is predicted to affect vulnerable calcifying species. As calcifiers play important roles ecologically and economically, understanding the nature of these effects on varying life stages is vital to understanding the impacts on marine ecosystems.

The overall objective of this body of work is to identify the physiological costs of resilience to OA in combination with pathogen stress in the eastern oyster (Crassostrea virginica) and hard clam (Mercenaria mercenaria). We also aim to identify the mechanisms and molecular features underlying acclimation and adaptation to OA. This project combines physiological assays and next generation sequencing with a focus on early life stages (i.e. larvae and juveniles) to identify physiological effects and mechanisms for resilience.

Comparison between juvenile hard clams that were reared in normal versus acidified seawater and the resulting color change that occurred under OA

To date, we have identified several physiological costs associated with resilience to OA including enhanced susceptibility to infection, reduced growth, and increased metabolic rates. Our ongoing work aims to elucidate the molecular features associated with resilience in an effort to develop tools for a sustainable bivalve aquaculture industry that is robust to the predicted effects of OA. The identification of molecular processes important for adaptation will be vital for selecting traits necessary for the survival of wild populations and aquaculture stocks under OA.