Trophic Cascades in Salt Marsh Ecosystems
Resource Type
Duration
00:10:01Description
In this video, ecologist Brian Silliman explains how he uses manipulative field experiments to study salt marsh ecosystems. His approach revealed that these systems are under top-down control from consumers and predators.
Salt marshes were once considered examples of bottom-up regulation in which population sizes are determined by abiotic factors and nutrient availability. Silliman observed that salt marsh grass was often covered with snails and wondered what the snails were eating. Through a series of cage experiments, Silliman demonstrated that the snails control the amount of marsh grass by facilitating a fungal infection that impedes the growth of the grass. He also showed that blue crabs control the number of snails and thereby protect the marsh grass from overgrazing. This is an excellent example of how confronting a long-held assumption with data can refine our understanding of the natural world.
An audio descriptive version of the film is available via our media player.
Key Terms
abiotic, facilitation, fungus, grass, infection, nutrient, overgrazing, scientific methodology, scientific process, species interaction
Primary Literature
Silliman, Brian R. and Jay C. Zieman. “Top-Down Control of Spartina alterniflora Production by Periwinkle Grazing in a Virginia Salt Marsh.” Ecology 82, 10 (2001): 2830–2845. https://doi.org/10.2307/2679964.
Terms of Use
Please see the Terms of Use for information on how this resource can be used.
Accessibility Level (WCAG compliance)
Version History
NGSS (2013)
HS-LS2.C
AP Biology (2019)
ENE-1, ENE-3, ENE-4, SYI-1, SYI-2, SYI-3
IB Biology (2016)
4.1, 4.2, C.2, C.3
AP Environmental Science (2020)
Topic(s): 1.3, 1.9, 1.11
IB Environmental Systems and Societies (2017)
2.1
Vision and Change (2009)
CC2, CC5