Keystone is the stone at the top of a roman arch. This stone keeps all other stones from collapsing the arch in on itself. You remove the keystone and the arch falls. As is with any keystone organism.

Other organisms depend on oysters and the habitat they create in order to survive. You remove oysters from the ecosystem and the food webs and biodiversity break down. Hundreds of species have been documented to live on and around oysters. Scroll below to see some species that co-exist with oysters