Jeff Clements, Matthew George

Numerous studies have documented weakened byssal attachment strength under ocean acidification (OA); however, a comparable number report no effect, even within the same species. We used meta-analysis to explore factors that could potentially explain observed effect size variation in byssal attachment strength following OA exposure. A systematic literature search uncovered 19 studies experimentally testing the impact of OA on byssal attachment strength (or some proxy thereof). Meta-analysis revealed body size (mean shell length) to be the strongest predictor of effect size variation, with a negative linear relationship observed between body size and effect size. Despite this relationship, no single study or experiment included body size as a moderating factor. Our finding that the byssal strength of larger bivalves is more susceptible to negative OA effects runs counter to prevailing wisdom that larger, older animals of a given species are more robust to OA than earlier life history stages. This highlights that body size and age may be important factors that determine OA sensitivity in adult calcifiers. In addition to body size, a critical review of each study revealed commonly neglected factors that could influence byssal thread attachment strength which we highlight to provide suggestions for future research in this area.