Salt Marsh Cordgrass Is Consumed by Herbivorous Marsh Periwinkle Snails

Multiple Choice

Salt marsh cordgrass is consumed by herbivorous marsh periwinkle snails, which in turn are consumed by blue crabs. Research has shown that cordgrass productivity is controlled ____.

A) indirectly by the abundance of snails
B) indirectly by the abundance of snail predators
C) directly by the abundance of snail predators
D) directly by the availability of nutrients in the salt marsh
E) indirectly by the amount of sunlight penetrating the water