We performed a common garden experiment where juveniles of blue mussels with different historical contact with crabs were exposed to either a control environment, crab chemical cues, low pH (as a proxy for ocean acidification), or a combination of low pH and crab cue. After 120 days raising, we measured the final shell length, shell thickness, shell mass, tissue mass and shell strength of blue mussels.

Predator functional response is a key element of feeding interactions that quantify the per capita feeding rates of predators depending on prey density, and variation in its parameters is strongly associated with interaction strength and population dynamics. We studied 18 functional responses of the marine whelk-bivalve systems across three levels of predator body size and three prey species at two habitat structures. We found that the marine whelk can be a handling-limited predator which received less attention so far. We propose that the handling-limited predator can further be categorized into two types: pursuing-limited (where maximum feeding rate could be influenced by habitat complexity) and ingesting-limited (where maximum feeding rate is impacted not by habitat complexity, but predator-prey body mass ratios and prey defense strategy). Our results show that handling time scales negatively with predator-prey body mass ratios, but there are layers of complexity nested within this trend. We first provide an underlying mechanism of this trend is the transition from handling to digestion limitation with increasing predator-prey body mass ratios. In addition to confirming known body mass ratios and habitat structure effects, our study confirms the importance of prey types. Our study reveals that simple assumptions about body masses and prey defense strategy may usefully refine estimates of feeding interactions in complex food webs.

Carbon dioxide-induced ocean acidification are producing a range of new selection pressures on marine calcifying organisms that show phenotypic plasticity in their shell morphology in response to predators. Although there are numerous studies on the effects of ocean acidification and predation risk on marine bivalves in isolation, the understanding concerning their combined effects is still lacking. To bridge this gap, we conducted a long-term mesocosm experiment using mussel populations with different history of predator exposure: crab-experienced and crab-naïve. Mussels were exposed to either lower pH or crab cue and the combination of both these treatments for four months. We demonstrate that both crab-experienced and crab-naïve mussels have heavier, thicker, rounder and, thus, stronger shells in response to crab cues, whereas low pH significantly decreased shell mass, thickness and strength. Mussels with previous experience to crabs showed greater plasticity in response to crab cues than crab-naïve mussels. However, this differential response was eliminated by ocean acidification. Exposure to low pH and crab cue resulted in antagonistic interactions for all traits, except for shell length where the combined effect was additive. However, there was no difference among populations in the interaction type for any of the traits. Our study may provide implications for the management of mussel populations under climate change.

Climate change and anthropogenic activities are producing a range of new selection pressures, both abiotic and biotic, on marine organisms. Although it is known that climate change can differentially affect fitness-related traits at different trophic levels of the food web, it is not clear if different trophic levels will respond via phenotypic plasticity in the form of maintenance of phenotypes in the face of abiotic and biotic environmental stress similarly. To answer this question, we combined a mesocosm experiment (120 days) using a food web comprising three gastropod species from two trophic levels (grazers and meso-predators) and a meta-analysis including 38 studies to address whether different trophic levels exhibit similar phenotypic responses to abiotic and biotic variables. Abiotic (ocean acidification) and biotic (predation) stress significantly influenced body mass, shell mass, shell thickness, and shell strength in both grazers and meso-predators in the mesocosm experiment, with the magnitude of OA effects greater on the meso-predator than the grazers; a result supported by the meta-analysis. In contrast, both mesocosm experiment and meta-analysis found that predation risk induced stronger responses in shell morphology for grazers compared to meso-predators. Together, our findings indicate that higher trophic level species are better able to maintain aspects of their phenotype under OA, suggesting that they may show greater tolerance to climate change effects in general, while lower trophic levels express higher levels of plastic inducible defences to maintain function when under threat of predation. By using marine snails as a model, our study provides new knowledge for understanding how changing environmental conditions may alter biological interactions, and increases our understanding of how climate change may affect ecological communities in which gastropods play a key role.

Climate change and anthropogenic activities are producing a range of new selection pressures, both abiotic and biotic, on marine organisms. Although it is known that climate change can differentially affect fitness-related traits at different trophic levels of the food web, it is not clear if different trophic levels will respond via phenotypic plasticity in the form of maintenance of phenotypes in the face of abiotic and biotic environmental stress similarly. To answer this question, we combined a mesocosm experiment (120 days) using a food web comprising three gastropod species from two trophic levels (grazers and meso-predators) and a meta-analysis including 38 studies to address whether different trophic levels exhibit similar phenotypic responses to abiotic and biotic variables. Abiotic (ocean acidification) and biotic (predation) stress significantly influenced body mass, shell mass, shell thickness and shell strength in both grazers and meso-predators in the mesocosm experiment, with the magnitude of OA effects greater on the meso-predator than the grazers; a result supported by the meta-analysis. In contrast, both mesocosm experiment and meta-analysis found that predation risk induced stronger responses in shell morphology for grazers compared to meso-predators. Together, our findings indicate that higher trophic level species are better able to maintain aspects of their phenotype under OA, suggesting that they may show greater tolerance to climate change effects in general, while lower trophic levels express higher levels of plastic inducible defences to maintain function when under threat of predation. By using marine snails as a model, our study provides new knowledge for understanding how changing environmental conditions may alter biological interactions, and increases our understanding of how climate change may affect ecological communities in which gastropods play a key role.