Abiotic & Biotic Control on PFTs
Resource availability, periwinkle herbivory,
and plant age
Salt marshes are nutrient-limited ecosystems threatened by anthropogenic nutrient loading and runaway consumption by herbivores. Yet, we know little about how these stressors shape saltmarsh plant traits and antiherbivore defenses, which influence trophic interactions and ecosystem resilience. In this mesocosm study, we tested the framework provided by the resource availability hypothesis (RAH) to assess how these stressors, eutrophication and herbivory, influence the defenses of Spartina alterniflora. We then built upon this framework by measuring each trait in both originally planted stems and clonally-grown new stems. (Wittyngham, Carey, & Johnson, 2023)
Mesocosms growing Spartina alterniflora using a mechanically-tidal system.
A marsh periwinkle (Littoraria irrorata) crawling on Spartina alterniflora in a mesocosm.
Consumer fronts shape saltmarsh plant traits and performance
Consumer-driven disturbance plagues ecosystems worldwide, and when high densities of consumers aggregate at the edge of a resource, they form consumer fronts. Our study focused on fronts created by the purple marsh crab, Sesarma reticulatum, as it consumed the smooth cordgrass, Spartina alterniflora. We found that Sesarma fronts altered vertical accretion capacity and reduced soil organic matter and sediment shear strength. Further, direct grazing by Sesarma reduced Spartina growth traits and defensive ability, presenting an additional pathway in which these fronts shape ecosystem function. (Wittyngham & Johnson, in review)
A purple marsh crab (Sesarma reticulatum).
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A consumer front created by Sesarma with experimental cages.
(Photo credit: Aileen Devlin | Virginia Sea Grant)