What is commonly referred to as "algae" on asphalt shingles, which is actually a type of bacteria?

The term "algae" in the context of asphalt shingles often refers to a specific type of bacteria known as cyanobacteria, which can thrive on roof surfaces under certain conditions. These microorganisms are capable of photosynthesis and can produce a greenish or dark stain that resembles traditional algae. While they are not true algae, they are often colloquially named as such due to their similar appearance and growth habits.

Understanding this distinction is important for homeowners and inspectors alike when diagnosing roof conditions. Effective treatment and prevention strategies can vary significantly depending on whether the issue is caused by bacteria, fungi, or actual algae. In this case, selecting the option that specifies bacteria provides a more accurate identification of the microorganisms responsible for the staining seen on asphalt shingles.