Effects of acute hyposalinity exposure on growth of blue mussels ( <i>Mytilus edulis</i> ) following settlement

ABSTRACT Larval experience has been shown to impact the phenotype of later developmental stages. Although exposure to low salinity negatively impacts both larval and juvenile blue mussels (Mytilus edulis), the effects of acute low salinity experienced by mussel larvae on juvenile performance have not been directly assessed. To test if larval exposure to hypoosmotic conditions has an impact on juvenile mussel phenotypes (i.e. carryover effect), we compared the growth rate from 0 to 35 days postsettlement for mussels that experienced short-term, hypoosmotic treatment at two different larval stages. We found evidence that a carryover effect of low salinity exposure on juvenile growth rate occurs but was dependent on when during larval development the exposure was applied. The growth rate of juvenile mussels exposed to hyposaline conditions as pediveliger larvae had a strong, negative impact on juvenile growth rate, including when the stress was also applied postmetamorphosis. However, this effect was not as pronounced when low salinity stress was applied when larvae were veligers. In total, our data indicate that stress from low salinity exposure can carry over to later developmental stages in M. edulis, and these carryover effects occur even when the duration of larval exposure to low salinity is only 24 h. Collectively, these findings suggest that juvenile performance may be negatively impacted if episodic flooding events occur during the spawning season, potentially acting as a driver for climate-induced shifts in M. edulis distributions.