In the current study, we assessed the effects of pH stress (7.5, 8.0) over a short timescale (48 hours) and the effects of pH stress (7.5, 7.6, 8.0) across two life history stages (larval, juvenile) of the Atlantic slippersnail Crepidula fornicata. Whole genome gene expression profiles under reduced pH (7.5, 7.6) were compared to those of snails reared at pH 8.0. Transcriptomic responses were compared to phenotypic responses (shell length, shell length growth rate, tissue weight, shell weight, metamorphosis ability). We wanted to determine how these snails, known to be resilient and invasive, are impacted by ocean acidification.