What would happen if Great White Sharks went extinct?

The ecosystem of the ocean is basically bigger fish eat smaller fish that eat smaller fish that eat algae. If they went extinct, there would be to many medium fish eating then causing those smaller fish that eat algae to die out, thus creating a domino effect. Because then, the algae would take over the coral reefs, causing animals who claim it as their home to die out. Thus causing a largely overload on the medium fish, who will later have no more smaller fish because their habitat has been destroyed, will mean a barren and dead ocean.