At the same time mercury was found in local fish at such high levels that consumption warnings were posted for fishermen. A Florida panther was found dead with levels of mercury high enough to kill a human. Scientists found that power plants and incinerators using fossil fuels were expelling mercury into the atmosphere, and it fell as rain or dust during droughts. The naturally occurring bacteria that reduce sulfur in the Everglades ecosystem were transforming the mercury into methylmercury, and it was bioaccumulating through the food chain. Stricter emissions standards helped lower mercury coming from power plants and incinerators, which in turn lowered mercury levels found in animals, though they continue to be a concern.