In 1993, Chisso Co Ltd began dumping mercury into the Minamata Bay. Bacteria in the bay changed the mercury waste into Methyl Mercury, which is deadlier than Mercury.
Chisso Co Ltd
Fish started to consume the Mercury and began to die. They then washed up on the beach and the fishes and crabs littered the Minamata's waters. After the fish started to die in 1950, they tested the crabs and fish and found that they were contaminated with large amounts of Mercury. The birds and cats that fed on the fishes died.