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Updated: May 8, 2026
Assessing Intertidal Populations of the Invasive European Green Crab
Published on: September 16, 2020
Crabs mediate interactions between native and invasive salt marsh plants: a mesocosm study.
Xiao-Dong Zhang1, Xin Jia, Yang-Yun Chen
1Coastal Ecosystems Research Station of the Yangtze River Estuary, Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, Shanghai, China ; Key Laboratory of Wetland Services and Restoration, Institute of Wetland Research, Chinese Academy of Forestry, Beijing, China.
Soil disturbance by crabs benefits invasive Spartina alterniflora by increasing soil nitrogen. This crab activity enhances invasive species growth, potentially outcompeting native plants like Phragmites australis and Scirpus mariqueter.
Area of Science:
- Ecology
- Plant Community Dynamics
- Invasive Species Biology
Background:
- Soil disturbance is a key factor in plant community structure and dynamics.
- Soil reworkers can increase habitat complexity and invasion risk, but their role in native-invasive species interactions is unclear.
- Crab activities may influence salt marsh ecosystems by altering soil nitrogen availability.
Purpose of the Study:
- To investigate the indirect effects of crab activities on the interactions between invasive Spartina alterniflora and native Phragmites australis and Scirpus mariqueter.
- To determine how crab disturbance affects soil nitrogen dynamics and plant performance in salt marsh mesocosms.
- To assess the impact of crab activities on competitive interactions between invasive and native salt marsh plants.
Main Methods:
- A two-year mesocosm experiment was conducted with five species combinations (monocultures and pairwise mixtures).
- Crabs were included or excluded in each combination to assess their impact.
- Plant performance (ramet-level and plot-level) and soil nitrogen availability were monitored over the experiment duration.
Main Results:
- Crab activities mitigated soil nitrogen depletion over the two-year experimental period.
- Plant performance, including height, biomass, and density, was enhanced by crab presence for all studied species.
- Crab disturbance favored invasive Spartina alterniflora over native Phragmites australis and Scirpus mariqueter, indicating altered competitive dynamics.
Conclusions:
- Crab activities can alleviate soil nitrogen limitation in salt marsh ecosystems.
- Crab disturbance promotes plant growth and clonal propagation, with plot-level performance being more sensitive than ramet-level.
- By enhancing soil nitrogen and promoting Spartina more than native species, crab activities may increase the competitive advantage of invasive Spartina over native Phragmites and Scirpus.
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