Not at all uncommon when applying new mulch. No harm will come to your plants whatsoever - it's just odd looking. It will disappear when things begin to dry out . Wet, humid conditions, especially on fresh wood mulch is the ideal situation for these. As far as getting rid of it, you can just rake it in, or you can wait for the weather to dry out.

No chemicals that I'm aware of to deal with it. Even if there were, it wouldn't be worth it considering how soon it's going to be gone naturally.

Thanks for the assuring feedback gsweater!