A couple of ponds in the Whiskeytown National Recreation Area are contaminated with a potentially dangerous algae. One pond is along Grizzly Gulch and the other one is called Second Pond. Cyanobacteria has been known to make people sick and kill dogs after swimming in waters where it’s present. It could be caused by stagnant water, higher temperatures and increased nitrogen from the Carr Fire runoff. It’s called blue-green algae but it comes in various colors and generally forms a scum layer or floating mats on the surface. Dogs who contact it should be thoroughly washed.