What are these critters??

[AandA]

By "plume" I assume ya'all mean the white stuff/growth.  Well.... It varies.  sometimes it is a very small amount, covering only an inch or two of surface, like is seen in the previous photo.  Sometimes it covers an area of a foot or more.  Below is yet another photo taken in Caribou three years ago.  As I said earlier, I hope to get a better photo yet this summer.  I'm also thinking about how to get a really good macro photo of one of the little fellers.  I know Maxfactor (Joe) has seen my baster that I use in the winter to inject hot water into the gloves of divers.  I'm thinking of using it as an ersatz slurp gun.  In this manner I could catch one and bring it up.  I just need to figure out some container to place it in the will be clear and small enough to restrict its movement so I can get a clear photo.