| Summary: | Rising atmospheric carbon dioxide levels lead to a phenomenon known as ocean acidification (OA). Due to OA, ocean pH is predicted to drop to ~7.8 by the end of the 21st century. These changes affect the distribution, physiological performance, morphology, and behavior of marine invertebrates. For predator–prey interactions, the ultimate outcome depends, in part, on how OA affects specific predators. Although elevated CO2 increases the activity level of predators, chemoreception is essential for foraging. The ability to detect food sources from a distance is crucial for predators, and reduced seawater pH adversely affects this chemosensory behavior. In contrast, damaging effects of low pH on morphological defenses in prey species (e.g., shell formation) significantly impact vulnerability to predation. Since predation rate in marine invertebrates is still affected even when elevated CO2 does not result in impaired morphology of the organisms, it can be concluded that sensory impairment via low-pH induced compensatory mechanisms is a key driving factor of predation rate, and that the underlying cause of varying predation rates cannot solely be attributed to morphological differences. Despite the distinct anatomical differences induced in organisms by low pH, I propose that as OA worsens, disruptions to sensory and chemical communication systems will become the dominant factors affecting predation rates. The rate of change in seawater chemistry is unprecedented, and evidence suggests that these changes in species distributions, abundances, and interactions could propagate through multiple trophic levels and possibly lead to permanent alterations to the marine food web as we know it.
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