Elevated temperatures suppress inducible defenses and alter shell shape of intertidal mussel

As ocean temperatures continue to rise due to climate change, many questions remain on how coastal species will cope with a changing environment. The effects of increased temperatures on bivalves has been well examined through single-species studies, showing reductions in tissue mass, shell growth, oxygen uptake, feeding rates, and survival. However, the consequences of these effects on predator-prey interactions remain poorly understood. We examined how increased temperatures (30, 32, 34 degrees C) and the presence of water-borne predation cues from blue crabs (Callinectes sapidus) affected the morphology and growth rate of southern ribbed mussels (Geukensia granosissima), as well as their handling times when attacked by predatory crabs. Although southern ribbed mussels were able to survive under chronic heat stress, exposure to higher temperatures resulted in more elongated shell shapes. Growth rates in mussel wet weight were higher for mussels reared in the presence of a predator than in the predator-free control, but only in the low-temperature treatment. Likewise, handling times were greater for crabs eating mussels grown in the presence of a predator, but the effect was lost at the mid- and high-temperature treatments. These findings suggest that predation-induced defenses were suppressed when prey were under chronic thermal stress, which could make mussels more vulnerable to predation. The presence of predation cues in natural environments should be taken in consideration when estimating or predicting the effects of climate change on organisms.