Ocean acidification refers to the process of oceans partially absorbing increasing carbon dioxide concentrations from the atmosphere, resulting in potentially corrosive conditions to marine life like shellfish, and Washington’s marine waters are particularly vulnerable.  The marine monitoring program added ocean acidification indicators to begin to understand baseline conditions and trends in Central Puget Sound. These indicators, such as total pH, are difficult to measure accurately and can be highly variable, contributing to the challenge of understanding long-term trends. This poster discusses some methods and approaches that King County uses to better assess ocean acidification indicators.