Dissertation Research: Periwinkle Grazing On and Control of Spartina Alterniflora.

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Project SummaryMany aquatic communities have been shown to be under top-down control, while most systemsdominated by vascular plants are assumed to be controlled by bottom-up forces. For nearly50 years, the prevailing paradigm in salt marsh ecology has been that bottom-up forces,such as nutrient availability, are the primary determinants of marshgrass production. Inthis proposal, we show that the standing crop of the dominant plant in western Atlanticsalt marshes is reduced wholesale and the substrate completely denuded when predators donot suppress densities of the most common grazing invertebrate in southeast marshes, theperiwinkle Littoraria irrorata. Before these results can be generally accepted, however,the apparent contradiction between our observations that Littoraria graze extensively onlive Spartina and the current paradigm which holds that Littoraria is the most importantdetritivore in the marsh system must be resolved. To do this, we present a detailedresearch plan to obtain a mechanistic understanding of the Littoraria - live Spartinainteraction. Results from this study will likely force us to reevaluate our currentunderstanding of marsh systems and add critical information to the ongoing debate as towhether or not vascular plant communities are susceptible to run-away consumer effects.