Ocean Acidification

Highlights

• Microhabitat variability modulates predator–prey interactions in rocky intertidal systems.
• Tide pool mussels experience recurrent hyposalinity and low pH conditions.
• Reduced shell resistance increases predation vulnerability in tide pool mussels.
• Fine-scale coastal heterogeneity drives trait-mediated trophic interactions.

Abstract

This study evaluates how the microhabitat of origin of the mussel Perumytilus purpuratus is associated with its vulnerability to predation by the crab Acanthocyclus hassleri. A comparison was made of individuals of P. purpuratus from three intertidal microhabitats: higher limit, lower limit, and tide pool (HL, LL, TP, respectively). The latter receives freshwater inputs associated with an adjacent stream and rainfall. Three environmental variables (salinity, temperature, and pH) and prey shell-breaking strength were measured, and predation experiments using single-prey and mixed-prey diets were also conducted. These experiments evaluated attack rate, handling time, attack zone, size of prey consumed, and crushing claw force. The results indicate that TP experience more extreme conditions, with lower salinity and pH during low tide compared with the other microhabitats (HL and LL). These conditions were associated with lower shell-breaking strength, which may reduce prey resistance to predator attacks. While attack rate remained similar across different diets, under a mixed diet, the predator A. hassleri showed greater consumption of mussels from TP. Tide pool prey also tended to require less handling time than prey from the other microhabitats. The anterior region of the prey shell (umbo area) was the most frequently attacked, regardless of the microhabitat. Smaller individuals from LL were more frequently consumed, whereas larger prey sizes were targeted in HL and TP. A. hassleri possesses the strength necessary to attack prey from all three microhabitats. Overall, these findings suggest that microhabitat-associated differences in shell characteristics may influence prey vulnerability to predation and shape prey selection by A. hassleri.

Sabja-Llanos E. N., Paredes-Molina F. J., Manzano M. E., Berkhoff T. D., Jaramillo H. N., Büchner-Miranda J. A., Salas-Yanquin L. P., Couto E. C. G., Pardo L. M. & Chaparro O. R., 2026. Microhabitat-driven variation in predator–prey interactions between the crab Acanthocyclus hassleri and the mussel Perumytilus purpuratus. Journal of Experimental Marine Biology and Ecology 605: 152229. doi: 10.1016/j.jembe.2026.152229. Article (subscription required).