Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

This dataset has also been contributed to Dryad, see related publications section. This dataset has been served at BCO-DMO at 2017-08-19 at BCO-DMO, but has only received a DOI on 2021-11-09. No changes were made to the dataset during that time.

Adult marine snails (Tegula funebralis) and sea stars (Pisaster ochraceus) were collected from mid-intertidal pools on the Bodega Marine Reserve (BMR) near Bodega Bay, California, in February and April 2014.  Snail and sea star size (mean ± se) were standardized as much as possible (snail height and diameter = 19.1±0.3 and 21.0±0.2 mm, respectively; sea star diameter = 143.3±9.0 mm). These sizes match those of many individuals involved in predator-prey interactions between these species in the field.  Immediately following collection, snails and sea stars were placed in separate flow-through aquaria at Bodega Marine Laboratory (BML) where they were allowed to acclimate to laboratory conditions for two weeks prior to experimentation. During acclimation, snails were fed kelp (Macrocystis pyrifera) and sea stars were fed T. funebralis individuals ad libitum. The latter protocol facilitated ‘dietary tagging,’ in which predators feeding on a particular prey species emit chemical compounds (likely originating from breakdown products of consumed tissue) that operate as especially strong anti-predator cues for that prey.  

Once animals had been acclimated to ambient seawater conditions, anti-Pisaster flight responses in the snails were assessed under multiple levels of altered seawater pH, in two separate five-day experiments. Five days is typical of the duration of low tide series that induce chronic exposure of rock-pool organisms to strongly depressed pH levels. In the first experiment, T. funebralis individuals were exposed to waterborne cue emitted by Pisaster under conditions of temporally constant pH (constant-pH experiment). In the second experiment, the pH of each treatment was varied semi-diurnally (fluctuating-pH experiment) to mimic temporal changes in pH that occur naturally in intertidal rock pools during many low tide series, in particular those for which pools become isolated from the adjacent ocean only at night (i.e., ~12 low tide series per year along the northern California coast, each lasting five days or longer).  

For additional details see: Jellison, B.M. et al., 2016.

pCO2 was calculated from daily alkalinity and pH using CO2SYS assuming dissociation constants from Mehrbach et al. 1973 as refit by Dickson and Millero 1987, and KSO4 from Dickson 1990.

Temperature, salinity, dissolved oxygen, and pH were measured using a YSI ProPlus Sensor.
Total pH was measured using a Sunburst SAMI spectrophotometric unit modified for benchtop use.
Total alkalinity was measured using a Metrohm 855 autotitrator.

NSF Award Abstract:
The absorption of human-produced carbon dioxide into the world's oceans is altering the chemistry of seawater, including decreasing its pH. Such changes, collectively called "ocean acidification", are expected to influence numerous types of sea creatures. This project examines how shifts in ocean pH affect animal behavior and thus interactions among species. It uses a case study system that involves sea star predators, snail grazers that they eat, and seaweeds consumed by the latter. The rocky-shore habitats where these organisms live have a long history of attention, and new findings from this work will further extend an already-large body of marine ecological knowledge. The project provides support for graduate and undergraduate students, including underrepresented students from a nearby community college. The project underpins the development of a new educational module for local K-12 schools. Findings will moreover be communicated to the public through the use of short film documentaries, as well as through established relationships with policy, management, and industry groups, and contacts with the media.

Ocean acidification is a global-scale perturbation. Most research on the topic, however, has examined effects on single species operating in isolation, leaving interactions among species underexplored. This project confronts this knowledge gap by considering how ocean acidification may shift predator-prey relationships through altered behavior. It targets as a model system sea stars, their gastropod grazer prey, and macoalgae consumed by the latter, via four lines of inquiry. 1) The project examines the functional response of the focal taxa to altered seawater chemistry, using experiments that target up to 16 discrete levels of pH. This experimental design is essential for identifying nonlinearities and tipping points. 2) The project addresses both consumptive and non-consumptive components of direct and indirect species interactions. The capacity of ocean acidification to influence such links is poorly known, and better understanding of this issue is a recognized priority. 3) The project combines controlled laboratory experiments with field trials that exploit tide pools and their unique pH signatures as natural mesocosms. Field tests of ocean acidification effects are relatively rare and are sorely needed. 4) A final research phase expands upon the above three components to address effects of ocean acidification on multiple additional taxa that interact in rocky intertidal systems, to provide a broad database that may have utility for future experiments or modeling.