Last fall the small Alaskan coastal village of Kivalina was inundated by a mysterious orange “goo”(click for photo). Locals and others suspected a toxic algal bloom (see here for image), or perhaps some sort of chemical release, or millions of microscopic “crustacean eggs”.
Yet just a month later the mystery substance was identified as none other than a plant-parasitic fungus called a rust — completely harmless to humans and aquatic life, and probably not bad plankton food.
Now, the identity of the rust has been revealed at last. It is the Spruce-Labrador Tea Needle Rust, Chrysomyxa ledicola, a parasite of both spruce trees and a rhododendron.
Source: Scientific American
This was an anomaly at the time but was it really? The article above notes that some observers noted that spruce trees were experiencing an epidemic of rust that summer. So much so that it formed a orange film on a lake 70 miles away from Kivalina. The prevalence of the rust spores along with some mechanism that concentrated them, caused this frightening situation. Investigation. This is how we learn.
Also note that some colored rains seem anomalous but are the result of spores or inorganic particles (sand or soot) in the air that turn the rain a color – yellow, red or black.