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

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 often-abundant 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.

Seasonality Determination by Oxygen Isotopic Profile: A Reply to Bailey et al.

A response is presented to the comment by Bailey et al. on the determination of seasonality of mollusk collecting using O-18 profiles of midden shells. Profiles were measured on two species of intertidal mollusks (Tegula funebralis and Collisella limatula) to provide further evidence for the applicability of the technique to seasonality studies.