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Shallow coastal environments are becoming more susceptible to marine heatwaves, particularly in Atlantic Canada, which is experiencing higher rates of ocean warming compared with the global average. Understanding bivalves' tolerance to heatwaves in Atlantic Canada is especially important, given the magnitude of bivalve aquaculture in this region. In this study, the physiological state of four commercially important bivalve species—blue mussel (Mytilus edulis Linnaeus, 1758), eastern oyster (Crassostrea virginica (Gmelin, 1791)), soft shell clam (Mya arenaria Linnaeus, 1758), and hard clam (Mercenaria mercenaria (Linnaeus, 1758))—was observed during a naturally occurring heatwave in Prince Edward Island, Canada. The metabolism, feeding physiology, and scope for growth of each species were compared. Results from this study, and comparisons with the literature, show interspecific variability in the metabolic rate and feeding physiology between species, but generally oysters, soft shell clams, and hard clams were less impacted during the heatwave compared with the blue mussels. Additionally, only the scope for growth of mussels declined throughout this experiment, which may be explained by cumulative heat stress, as temperatures experienced during this heatwave exceeded the thermal tolerance limits of mussels. [ABSTRACT FROM AUTHOR]