Mercury getting into the lake/water? We're always looking for the man made form, a leak from a plant. I was watching a kids program (Caption Planet) with my granddaughter years ago. There are 111 or so videos on Utube so it's kinda hard to find it. This big business pig looking guy wanted to build a lake. He wasn't going to remove any of the trees and brush from the valley before building the dam. Green wood expels mercury into the water as it ages. We add green wood for habitat so we are adding to the problem too.