Lobsters are an integral part of the Gulf of Maine ecosystem as well an economically significant fishery. We hypothesize that ocean acidification (OA) and rising temperatures will serve as multiple, synergistic stressors on larval and early benthic juvenile lobsters, resulting in decreased shell growth and changes in the shellsí mineral composition. In addition, we will investigate the effects of OA on lobster health through shell disease, given that this disease is a bacteria-based assault whereby the bacteria create low-pH conditions on the shell as a means of entry. Critical to understanding the mechanistic responses of lobsters to OA and increased temperature, as well as associated susceptibility to disease, is isolating the genetic controls on shell hardening. Physiological data such as enzyme activity and transcriptomics will be used to discover cellular responses to thermal stress and acidosis. This laboratory-based study will track lobster larvae as they metamorphose to benthic juveniles in aquaria under experimental conditions. Data from specimens exhibiting shell disease will be examined across all treatments and disease states, comparing the enzymatic activity of Na+/K+ ATPase (acid-base regulation) to respective changes in gene expression 100s to 1000s of other genes encoding proteins known to be involved in acid-base and ion regulation, protein biosynthesis, and cellular stress responses. The transcriptomic analyses will be correlated to shell mineralogy, structure, growth, disease, and survival.