Copper pollution of marine environments has been identified as a persistent problem in urban areas of Southern California. Regulations for copper contamination in Southern California’s harbors must be considered in the context of a changing global ocean, particularly its combined effect with ocean acidification. Mytilus is the most sensitive genus to copper toxicity as well as an ecologically and economically important native organism in Southern California. This project will monitor the survival, development, and gene expression of mussel larvae of the genus Mytilus in response to both defined and field-collected copper-contaminated water samples, under pH conditions that simulate present day, 2050, and 2100 predicted levels. The project objective is to predict the effect that ocean acidification will have on the sensitivity of marine invertebrates to copper contamination.