[Tony Niar Brain]

Yes, something would have to eat the mercury, OR, something would have to eat someting else that is already contaminated with mercury. This is where the "food chain" that we all learned about in grade school comes into play. Mercury gets into plankton, which gets eaten by bugs or small fish, which get eaten by bigger fish, which get eaten by humans. Plus, you could have contamination of ground water, which would affect much more than fish in a lake.

[TroutStalker]

something would have to eat the mercury

Almost forty years ago, at age fifteen, I had abdominal surgery, and had a tube into my stomach weighted with mercury. When they withdrew it, the pouch of mercury ruptured, and I swallowed approximately 10 cc of mercury.

I never suffered any ill effects from that, or from playing with mercury as a kid, or even playing with asbestos as a kid. Oh, and we used to ride our bicycles behind the truck fogging for mosquitos using diesel fuel and DDT, happily inhaling gobs of the stuff.

I guess living dangerously had no effect on me. (And we had guns and knives as well.)