What is black streaks (roof algae)?
Black streaks on roof shingles caused by Gloeocapsa magma algae that thrives in humid, shaded conditions and spreads through moisture and airborne spores.
Gloeocapsa magma is a photosynthetic algae that produces dark pigmentation to protect itself from UV rays. When it colonizes asphalt shingles, it creates the characteristic black or dark green streaks that typically run down the roof slope. The algae feeds on the limestone filler material in shingle granules, slowly degrading the roof surface while establishing itself over months or years.
Myrtle Beach's humid subtropical climate and coastal salt spray create ideal conditions for this algae to thrive. High moisture from ocean air, frequent cloud cover, and the shade cast by mature trees around homes all reduce shingle drying time and encourage spore germination. The algae spreads through airborne spores that travel from infected roofs to neighboring properties, which is why you often see the problem affecting multiple homes in the same area.
While black streaks are primarily a cosmetic issue in their early stages, the algae's feeding weakens shingle integrity and can eventually cause premature roof degradation. Mold and moss often follow algae colonization, accelerating damage. Property owners in Myrtle Beach typically address the problem through professional roof soft washing, which removes the algae without the high pressure that would damage granules or shingles.