What Are the Black Streaks on My Asphalt Roof?

Have you ever noticed an asphalt roof with black streaks that are stained on the roof? Usually they are in sections, but once in awhile you can see them all over the roof. Interestingly, it does not matter how old the roof is. You can see them on a roof just a couple of years old. What are they and how can you get rid of them?

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