Hi Tess, it looks like this is something called "insect egg slime mold". It isn't harmful and will disappear as the weather dries, (if in fact it ever does). You don't need to do anything. Slime molds are part of the decomposing organisms that keep our planet from being overcome with un-decomposed plant materials. 

Slime molds come in various shapes and colors. I'm including a link to a Stanford University web page on slime molds which has some great photos.

Enjoy!