Everyone knows the ocean provides great benefits to our island – from fishing and shellfishing, to tourism dollars, to the mild climate that we all enjoy. But oceans provide another relatively invisible service to the world at large. By absorbing large amounts of the excess CO₂ produced by our reliance on fossil fuels, the world's oceans act as a buffer to climate change, greatly reducing the warming we would have seen to date had all of that CO₂ remained in the atmosphere. Unfortunately, taking one for the team has come with a cost that is only beginning to be understood: the dissolved CO₂ produces carbonic acid that is gradually lowering the pH of the water.

This process – known as ocean acidification – will impact any marine organisms that are sensitive to pH (that is, most of them). Perhaps the most strongly affected are shellfish, who find it much more difficult to build their calcium carbonate shells as pH declines. It is a new area of research, but the studies are now coming quickly. For example, scientists found that clams, scallops, and oysters grew more slowly when CO₂ concentrations were raised to levels expected later this century; further, 50% fewer quahog and scallop larvae survived. Another study compared current conditions to those of the past, and found that quahogs and scallops grew faster, had thicker shells, and greater survival in pre-industrial CO₂ levels than in today's. Unfortunately, these lab studies may underestimate the effect of growth rate and shell thickness on mortality in the wild due to predation. The science is becoming increasingly clear that ocean acidification will have a very large impact of shellfish populations and the future course of the fishery.