In an intertidal community where the sea star, Pisaster ochraceus, feeds on mussels, Mytilus californianus, scientists removed the sea star to study the effect on species richness. Once the sea star was removed, the species richness of the community declined due to the mussels eliminating most of the invertebrates and algae. Which of the following describes the role of the sea star? The sea star is a foundation species that decreased the diversity of the community by having the largest biomass.

The sea star is a foundation species that exerted strong control over the community by limiting the population of the mussels.

The sea star is a keystone species that maintained the diversity of the community by limiting the abundance of the mussels.

The sea star is a keystone species that exerted strong control over the community due to high abundance in population.