Table of Contents

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

This dataset is part of a broader study conducted in the Gulf of Maine to investigate phenotypic plasticity of prey species in response to predator invasion and warming oceans:

1. Green crab surveys plus historical crab density data (dataset 990378) 
2. Green crab density from field studies at rocky intertidal sites from April 2019 to December 2021 (dataset 911365) 
3. Latitudinal (clinal) variation in Littorina obtusata shell thickness and tissue mass (dataset 990839)
4. Field experiment outplanting Littorina obtusata with predators (green crabs) to examine local and regional geographic variation in inducible defenses conducted from April to August 2021 (dataset 911221)
5. Morphological data from reciprocal transplant experiment in the field (this dataset)

​See Related Datasets section below for links and additional details.

To examine how shell thickness and its plasticity have changed after 20 years (1998-2018), we repeated a reciprocal transplant experiment in 2018 that had previously been conducted in 1998 (Trussell and Smith, 2000). To allow a robust comparison of the two experiments, we carefully replicated all aspects of the 1998 experiment including using the same experimental chambers that were deployed into the field 20 years earlier. In early May 2018, we collected juvenile Littorina obtusata (5-6 mm in shell length) from a northern and a southern site in the Gulf of Maine. The northern site was near Quoddy Head in Lubec, Maine (44.82, -66.97) and the southern site was Lobster Cove in Manchester, Massachusetts (42.56, -70.77). All snails were individually tagged with a color-coded dot of permanent ink that was then sealed with cyanoacrylate glue. We measured initial shell length and shell thickness with digital calipers (± 0.01 mm) and shell mass and tissue mass (± 0.001 g) were estimated using a non-destructive weighing technique (Palmer, 1982).

After completing initial measurements, we transported snails from both populations to the northern or southern site in mid-May. At each site, we placed six snails (hereafter, response snails) from a single population and approximately 60 grams of brown algae (Ascophyllum nodosum) as food into 24 separate, replicate cylindrical containers (5-cm height x 10-cm diameter) that had mesh windows (mesh size = 3mm) to allow water flow. Hence, at each site 12 replicate containers housed snails from either the northern or southern population and 6 replicates for each population exposed snails to either the presence (Crab) or absence (No Crab) of predation risk. To create these risk treatments, each container stocked with response snails was secured beneath a similar container that was perforated on all sides and housed either (a) a mature male green crab (Crab) and 30 conspecific snails (hereafter, stimulus snails) or (b) just 30 stimulus snails (No Crab) to serve as a control. Each pair of stimulus-response containers was placed inside a large, replicate cylindrical chamber (11-cm height x 28-cm diameter) that had mesh windows (mesh size = 3mm) to permit water flow. These large chambers were anchored haphazardly in the mid-intertidal zone (~1.5 m MLW). Ocean temperature was monitored at 5-minute intervals during the experiment with dataloggers (Tidbits, model UTBI-001, Onset Computer Corp.) that were placed inside three replicate chambers at each site. Every 14 days we replaced stimulus snails in both the Crab and No Crab containers. For appropriate replicates, we also confirmed that crabs were alive; any dead crabs were replaced immediately. Overall, we had to replace 7 crabs at the northern site and 7 crabs at the southern site. At day 45, we replaced the Ascophyllum that served as food for response snails in all replicates. After 90 days in the field, all response snails were returned to the Northeastern University Marine Science Center (Nahant, Massachusetts) for measurement of final snail shell length, shell thickness, and tissue mass.

- Imported original file named "2.Trussell.Corbett.Updated.ReciprocalTransplantExperiment.csv" into the BCO-DMO system.
- Renamed fields/columns to comply with BCO-DMO naming conventions.
- Saved the final file as "990830_v1_morphological_data_reciprocal_transplant.csv"

NSF Award Abstract:
Over the past two decades, the Gulf of Maine has experienced unprecedented warming that, among other things, has further enabled the invasive green crab to expand its range in rocky shore habitats. The adverse ecological impacts of this invasive predator have been documented worldwide. This study examines how geographic variation in the capacity of two common prey species to respond to the combination of this predator and warming ocean temperatures can shape prey feeding and performance and impact community structure and dynamics. Hence, this research enhances understanding of the evolution of phenotypes, their plasticity, and the nature of adaptation and its role in eco-evolutionary dynamics. More broadly, it informs understanding of how organisms and marine communities may respond to future environmental change. In addition, this project makes contributions to the STEM pipeline by providing middle and high school, undergraduate, and graduate students with cross-disciplinary training in evolutionary and community ecology. In collaboration with an institutional outreach program, the investigator is also developing web-based multimedia projects and teacher resource materials based on this research.

A central principle in ecology is that species residing in the middle of food chains must balance the benefits of eating with the risk of being eaten by their predators. Solving this foraging-predation risk trade-off often involves plasticity in prey traits with consequences for the evolution of adaptation and species interactions that drive community-level processes. Hence, the foraging-predation risk trade-off provides a powerful conceptual framework that links evolutionary and community ecology. Yet at the same time, other environmental stressors like temperature can shape this trade-off, adding complexity that makes it difficult to predict the capacity of organisms to adapt to environmental change and the consequences for communities. The investigator is conducting this study in rocky shore habitats of the Gulf of Maine (GOM) which have long been influenced by strong latitudinal temperature gradients and non-native species invasions. The overarching hypothesis is that predation risk and temperature are factors shaping geographic variation in plasticity and adaptation, with consequences for individuals, populations, and communities. First, the investigator is conducting field experiments to document geographic variation in the trait plasticity of two common prey species in the green crab's diet. Second, he is using reciprocal transplant experiments to examine trait plasticity in response to risk and water temperature, generating data to compare with similar experiments conducted in the late 90s prior to recent ocean warming and expansion in range of green crabs. Third, he is conducting a laboratory common garden experiment to evaluate the effects of risk and water temperature on trait plasticity. Finally, he is using reciprocal transplant experiments in the field to understand the interactive effects of risk and water temperature on prey foraging rates and the abundance of a species that plays an important role in intertidal community structure and dynamics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.