Dark black or green stains on your roof are not only unsightly and take away from the curb appeal of your home, they can also lead to the loss of structural integrity over time. The most common cause of streaking and discoloration on shingle roofs is the presence of gloeocapsa magma, a species of cyanobacteria. Gloeocapsa magma attacks limestone— a common ingredient in roofing shingles—causing it to dissolve and disintegrate at a rapid rate.
Even the beginning stages of Gloeocapsa magma can shorten the life of your roof, but the later stages are when loss of structural integrity becomes a greater concern. It is also at these later stages when a roof’s factory warranty can be negated or voided (depending on the manufacturer).