Salinity stress cross-tolerance of Ostrea lurida after exposure to acidified ocean conditions in a simulated freshet discharge

Abstract

Ocean acidification is widely regarded as a serious danger to marine organisms, especially calcifying invertebrates, but how this might interact with other abiotic stressors in realistic environmental events is less well modeled. Low salinity events in Washington state caused by snowmelt may increase in severity due to climate change, adding another stressor onto the backdrop of an already acidifying ocean. To test the effect of these asynchronous multi-stressors, we acclimated Olympia oysters Ostrea lurida to a gradient of pH conditions, after which we restored the pH and exposed them to low salinity, simulating a river freshet discharge. Our data indicate that shell thickness and respiration rates decrease with pH, regardless of salinity shock conditions. Calcification rates decreased with pH for oysters exposed only to ambient salinity, while calcification rates trended towards an increase in oysters exposed to the salinity shock. These findings could indicate a possible cross-tolerance in O. lurida, where exposure to increasingly acidic conditions could prepare them for short-term hyposaline shock.