Reference to a prefab in the script will increase memory usage?

I declare some public variables in a script, and assign prefabs to them in the inspector. Like this:
Then I found my app's memory usage increase by 10mb. (iOS platform)
When reference a prefab in the script, unity will load the prefab into memory even before instantiate it, right?
If this is true, it will be so sad! Because I made lots of effects, which will be...

Reference to a prefab in the script will increase memory usage?