Ocean acidification alters the response of intertidal snails to a key sea star predator

Abstract

Organism-level effects of ocean acidification (OA) are well recognized. Less understood are OA's consequences for ecological species interactions. Here, we examine a behaviourally mediated predator-prey interaction within the rocky intertidal zone of the temperate eastern Pacific Ocean, using it as a model system to explore OA's capacity to impair invertebrate anti-predator behaviours more broadly. Our system involves the iconic sea star predator, Pisaster ochraceus, that elicits flee responses in numerous gastropod prey. We examine, in particular, the capacity for OA-associated reductions in pH to alter flight behaviours of the black turban snail, Tegula funebralis, an oftenabundant and well-studied grazer in the system. We assess interactions between these species at 16 discrete levels of pH, quantifying the full functional response of Tegula under present and near-future OA conditions. Results demonstrate the disruption of snail anti-predator behaviours at low pH, with decreases in the time individuals spend in refuge locations. We also show that fluctuations in pH, including those typical of rock pools inhabited by snails, do not materially change outcomes, implying little capacity for episodically benign pH conditions to aid behavioural recovery. Together, these findings suggest a strong potential for OA to induce cascading community-level shifts within this long-studied ecosystem.

Ocean acidification alters predator behaviour and reduces predation rate

“…In self-righting trials, nine cone snails righted in each treatment after 30 min. There was no significant difference in righting time with CO 2 (t 16 …”

“…The prevalence of complex trophic interactions in marine ecosystems, often involving multiple species and indirect effects, means that behavioural alterations caused by elevated CO 2 levels are likely to make future ecosystem structure and function more difficult to predict. Increasing evidence for behavioural effects of elevated CO 2 on species at different trophic levels [3][4][5][6][7][8]12,15,16,18,20,21], including interacting species as demonstrated here, suggests that trait-mediated indirect interactions could be important in predicting the effects of ocean acidification on marine communities and deserve further attention [19].…”

“…However, we know little about the potential effects of ocean acidification on predatory behaviours in marine invertebrates, or the potential for ocean acidification to affect invertebrate behaviour across more than one trophic level. Several studies have shown that the response of invertebrate prey species to their predator is affected by high CO 2 [3][4][5]15,16], but how elevated CO 2 may affect the predators of these species has not been tested. For a temperate gastropod, one recent study showed that elevated CO 2 affected the avoidance of predator cues, but not cue detection of mussel prey [5].…”

Predatory strategies and behaviours in cephalopods are altered by elevated CO2

“…New studies have also demonstrated the behavioural impacts of elevated CO 2 on marine molluscs. For example, elevated CO 2 impairs predator avoidance behaviour in intertidal snails (Jellison, Ninokawa, Hill, Sanford, & Gaylord, ; Manríquez et al., , ). In the jumping conch snail, elevated CO 2 affects predator‐escape behaviour, reducing the proportion of snails that jump from a predator, and increasing the latency to jump, as well as altering the escape trajectories of snails that do jump to escape predation (Watson et al., ).…”

Species interactions can shift the response of a maerl bed community to ocean acidification and warming

“…Climate change is likely to strongly alter interactions between macroalgae (e.g. calcifying and noncalcifying macroalgae; Olabarria et al, 2013;Short et al, 2014Short et al, , 2015, interactions between grazers and macroalgae (Poore et al, 2016;Sampaio et al, 2017), and prey-predator dynamics (Asnaghi et al, 2013;Jellison et al, 2016), inducing drastic consequences on the structure and functioning of marine ecosystems (Widdicombe and Spicer, 2008;Hale et al, 2011).…”