As wild blue mussel seed declines in the Gulf of Maine, mussel growers are relying increasingly on hatchery production to stock their farms. While mussel populations are currently under pressure from predation by the invasive European green crab, ocean acidification (OA) is expected to be another stressor – especially among earliest life stage mussels – as climate change progresses. Traditionally, shellfish hatcheries have implemented seawater buffering to mitigate low pH in their incoming seawater. Here, live microalgae diet optimization is proposed as an alternative strategy for rendering blue mussel larvae inherently more resilient to OA in a hatchery scenario. Following an initial microalgae growth and nutritional analysis phase, 4 diets – each consisting of a flagellate and a diatom species – were created to emphasize different nutritional parameters (industry standard, high calorie, high DHA, high EPA/protein). A first experimental trial tested larval/early juvenile response (survival and growth) to a 2-level seawater pH treatment (7.80/present day, 7.30/year 2100) and a 4-level diet treatment, and a second experimental trial tested response to the pH treatment, a reduced 2-level diet treatment, and a 2-level seawater buffering treatment (soda ash buffering, no buffering). Each trial was followed by a field deployment of experimental mussels at each of 2 mussel farms in different locations along the Maine coast (Blue Hill Bay Mussels and Bangs Island Mussels) to reanalyze mussel responses after they achieved market size. The experimental trials tested the efficacy of diet optimization for improving blue mussel resilience to OA, as well as its interaction with seawater buffering.