As more carbon dioxide is added to the atmosphere, increasing amounts are absorbed into the oceans. This increase in total carbon, and consequent lowering of the ocean pH, has a variety of effects, many of which are only just beginning to be thoroughly studied. Preliminary results suggest that organisms with calcium carbonate shells may be particularly impacted by increasingly acidic seawater. We will be studying the impact of ocean acidification on marine organisms of the California coast, including the sea urchin, abalone and mussel. Beyond the scientific interest in trying to understand the affects of acidification on them, these organisms are of additional interest due to their economic and social value. The project will include the design and creation of a system, which can accurately monitor the carbonate chemistry of seawater, as well as the temperature and oxygen concentration. Some problems have been identified with many of the methods used in the past to change the composition of the seawater, such as bubbling with gas or acid additions. To avoid these and try to mimic the natural changes as closely as possible, we will pre-equilibrate the seawater using a membrane contactor between a mixture of the desired gases and seawater. Autonomous monitoring will ensure the tanks are at the desired level and the technique will allow for easy and non-intrusive adjustments to the carbon system.