Ocean chemistry is changing, and the main focus of attention has been ocean acidification, which occurs when increased CO2 uptake reduces available carbonate ions . Recent projections suggest, under high emission scenarios, that global average pH could decrease from 8.1 to 7.8 by the end of the century. However, ocean acidification hotspots (acidity increasing at a faster rate) occur due to regional factors such as coastal upwelling, changes in discharge rates from rivers and glaciers, sea ice loss, and urbanization.
Ocean acidification is a significant threat to shellfish. Increasingly acidic ocean waters can inhibit shellfish growth, lower survival rates, and populations. For example, in Chesapeake Bay increased growth rates in crabs, tied to lower pH, can lead to increased predation of oysters. Recent studies suggest that competitive interactions among species may shift, putting shellfish at a relative disadvantage.