Yellowstone's Morning Glory pool turned green by tourist's good luck coins, say researchers

No, this isn't some St. Patrick's Day joke.

Researchers say that Yellowstone National Park's world-famous Morning Glory thermal pool is turning a yellowish-green by decades of tourists throwing coins for good luck and from trash and other natural debris.

The once crystal clear lagoon, images reveal a dramatic change since the 1940s.

"Over the years, however, tourists have tossed lucky coins, rocks, and other debris into the pool, partially blocking the underground heat source and lowering the temperature of the spring to a range habitable by photosynthetic microorganisms that probably didn't live there before," Adam Hoffman, explains in Science Friday.