Do you mean a white residue resting on kelp? No need to be alarmed. These whitish bits are actually natural sugars or precipitated salts that have formed.
This is what some candy companies use to dust their candies, such as chewing gum.
Thinking of getting rid of it? Just leave a damp paper towel in the jar of seaweed for a couple of days. This will perk up the seaweed.
