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

Brown University, Providence RI

Investigators

Abstract

Project Summary Many aquatic communities have been shown to be under top-down control, while most systems dominated by vascular plants are assumed to be controlled by bottom-up forces. For nearly 50 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. In this proposal, we show that the standing crop of the dominant plant in western Atlantic salt marshes is reduced wholesale and the substrate completely denuded when predators do not suppress densities of the most common grazing invertebrate in southeast marshes, the periwinkle Littoraria irrorata. Before these results can be generally accepted, however, the apparent contradiction between our observations that Littoraria graze extensively on live Spartina and the current paradigm which holds that Littoraria is the most important detritivore in the marsh system must be resolved. To do this, we present a detailed research plan to obtain a mechanistic understanding of the Littoraria - live Spartina interaction. Results from this study will likely force us to reevaluate our current understanding of marsh systems and add critical information to the ongoing debate as to whether or not vascular plant communities are susceptible to run-away consumer effects.