[TheForge] OT - Asphalt shingle rot? (Lichen)

[Bruce Freeman]

So I went up on the roof today to do a little maintenance, and where I
leaned my ladder there was this big "splotch."  "Bird turd," I
thought.  But then I saw similar splotches all over the roof (like, a
dozen or two), ranging from 1/2" to 2" diameter.   And they only
occurred on the northern slope of the roof.  Looking closer, I saw
they weren't turds but lichens!

I've never heard of lichens growing directly on (mineral surfaced)
asphalt shingles.  Is this common?  Any remedy?  I considered straight
bleach, but my gutters are aluminum.

-- 
Bruce
NJ