HHMI made this amazing video about trophic cascades a few weeks ago.  I HIGHLY recommend watching this. Featuring kings of ecology Jim Estes and Bob Paine

http://www.hhmi.org/biointeractive/some-animals-are-more-equal-others-keystone-species-and-trophic-cascades

Like the video says, Paine’s research inspired an explosion of studies in different ecosystems about the role of keystone species.  Salt marshes have too shown to be dominated by keystone species!  Trophic cascades have been found in salt marshes in the Southeast and in New England, where predators such as fish, blue crabs, or terrapins control the density of Spartina alterniflora consuming herbivores.  Trophic cascades and keystone species are, in my opinion, some of the most exciting aspects of community ecology!