To examine the impacts of fear removal on the strength of trophic cascades, we measured the amount of algae (Ulva spp.) consumed by Tegula funebralis that either displayed either an anti-predatory response to its predators, Pisaster ochraceus and Cancer productus, or ignored the predators. Additionally, we used two species of predators with differing consumption rates to test how predator traits might mediate the effect of removal on trophic cascade strength. The experiment was conducted within laboratory mesocosms at Bodega Marine Lab in 2018. This dataset reports results for experiments with Cancer productus as the predator. See "Related Datasets" section for results from the experiments with Pisaster ochraceus as the predator.

Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • BCO-DMO Processing Description
• Related Datasets
• Parameters
• Project Information
• Funding

To examine the impacts of fear removal on the strength of trophic cascades, we measured the amount of algae (Ulva spp.) consumed by Tegula funebralis that displayed either an anti-predatory response to its predators, Pisaster ochraceus and Cancer productus, or ignored the predators. Additionally, we used two species of predators with differing consumption rates to test how predator traits might mediate the effect of removal on trophic cascade strength. The experiment was conducted within laboratory mesocosms at Bodega Marine Lab in 2018.

Pisaster ochraceus, Cancer productus, and Tegula funebralis were collected along the coastline of Sonoma County, California in 2018. Both Pisaster and Tegula were sampled at Carmet Beach (38.372172 N, -123.076438 W), and the Cancer crabs were gathered subtidally from Doran Beach (38.309334 N, -123.048703 W).

When conducting the fear and no-fear treatments for Tegula, we had 20 mesocosms with ten Tegula each when paired with Pisaster as the predator. Ten of the mesocosms were used for the fear treatment where we introduced Pisaster cues from a secondary container to provoke a behavioral fear response in Tegula. The other ten mesocosms contained no Pisaster cues and represented the no-fear treatment. In the fear treatment, we culled Tegula at the baseline rate of 8% per day, and we culled Tegula at the enhanced rate of 33% per day in the no-fear treatment.  Ulva sp. was used as the basal resource with Tegula, and we measured the change in Ulva weight over the duration of the experiment. We dried the Ulva for two hours before weighing them. We also had ten mesocosms with just seawater and Ulva as a control to measure the natural degradation of Ulva over the course of the experiment.

We conducted similar fear and no-fear treatments with Tegula except paired with Cancer as the predator. The contrast in the effect of fear on the trophic cascades between the two predators shows how predators of differing dangerousness can influence the role of fear in trophic cascades. Like the Pisaster-Tegula experiments, we used 20 mesocosms with ten Tegula each for the Cancer-Tegula experiments. We used ten of those mesocosms for the fear treatment where Cancer cues are introduced to provoke a behavioral fear response and used the remaining ten mesocosms for the no-fear treatment. In the fear treatment, Tegula were culled at the baseline rate of 34% per day, and in the no-fear treatment, Tegula were culled at the enhanced rate of 57% per day, simulating Cancer predation rates.

To analyze the role of fear and predator identity on amount of algae consumed by Tegula, we ran a generalized linear model with a gamma distribution to account for the heteroscedasticity in the amount of algae consumed. Predator identity and the presence of fear were used as fixed effects. We followed up each generalized linear mixed effects model with explicit a priori planned contrasts with either a Bonferroni or Tukey correction. For Tegula, we compared whether afraid snails consumed significantly different amounts of algae for each predator and whether that difference was different between predators.

Organism identifiers:

Scientific Name, Life Science Identifier (LSID)
Pisaster ochraceus,urn:lsid:marinespecies.org:taxname:240755
Cancer productus,urn:lsid:marinespecies.org:taxname:440382
Ulva spp.,urn:lsid:marinespecies.org:taxname:144296
Tegula funebralis, urn:lsid:marinespecies.org:taxname:534190

 

* The originally provided "Pisaster tegula phase 3 stats.csv" with no modifications was packaged along with related dataset (947753) files and R-scripts into Algal_consumption_analysis_package.zip and attached as a supplemental file.

* Table from submitted file "Pisaster tegula phase 3 stats.csv" was imported into the BCO-DMO data system for this dataset.
** In the BCO-DMO data system missing data identifiers are displayed according to the format of data you access. For example, in csv files it will be blank (null) values. In Matlab .mat files it will be NaN values. When viewing data online at BCO-DMO, the missing value will be shown as blank (null) values.

* Column names adjusted to conform to BCO-DMO naming conventions designed to support broad re-use by a variety of research tools and scripting languages. [Only numbers, letters, and underscores.  Can not start with a number]

* Date converted to ISO 8601 format

* ISO DateTime with timezone (UTC) column added in ISO 8601 format.

* Taxonomic identifiers added to the metadata (Life Science Identifiers (LSID)). Names matched using the World Register of Marine Species (WoRMS) on 2024-01-02.

* Bounding box for dataset determined by sampling locations provided and location of experiment at Bodega Bay Marine Laboratory (38.3180548,-123.0743098).

Coverage: Central California coast, USA

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.