dried leaves smell in my hot water

When I run the hot water I swear I can smell something that's kind of like the smell/taste you get when you're raking leaves. I'm pretty sure this is just hot water, not cold. A search here turned up references to sulfur smells having to do with bacterial infections, but this doesn't smell sulfury to me. Has anyone smelled this or have opinions for what I should try to get rid of it?

I have a gas water heater, by the way.

Thanks.