To survive in the intertidal zone, aquatic organisms have adapted specialized exteriors. Sea stars have thick skin, mussels have hard shells, and rockweed algae have a rubbery exterior. Which tidal process causes such adaptations to be necessary in the intertidal zone?

When the tide comes in, predator organisms arrive.

When the tide comes in, water salinity increases.

When the tide recedes, food resources decrease.

When the tide recedes, organisms are exposed to the air.