There's plenty of evidence that unusually large and frequent volcanic eruptions caused massive climate change during this period of mass extinction, so mercury was just another factor, although, from the measurements in this study, an important factor.

If the theory that the volcanoes burned through coal beds is correct, the climate change and the mercury spikes may both be related to the mercury content that is commonly found in coal and which makes burning coal to power incandescent lightbulbs a larger source of mercury in the environment than the fluorescent lightbulbs that contain traces of mercury.

As the article says, algae sequester mercury normally. Presumably so do the plants that form coal seams. When this sequestration is reversed, mercury can rise to dangerous levels.

Coal-burning is once again shown to be environmentally unsafe. It not only poisons the air, water and soil through acid rain, but it also emits large amounts of NOx and heavy metals, and produces global warming gases. Furthermore, most fertilizer is made with natural gas, and petroleum products add to the pollution and the overloading of the natural cycles of nitrogen, carbon, sulphur, heavy metals, etc.

What Nature buries should often stay buried. Geology and ecology are vital parts of the cycles which make the Earth inhabitable and prevent it from becoming a toxic, runaway greenhouse world like Venus, or a dead icy ball, like Mars.

The more we study mass extinctions and dead worlds, the more we learn that we are risking the creation of one by our meddling in the dynamic balance of geology and biology which James Lovelock named Gaia (narrow sense).

AbbeySomeone: As someone who became debilitated due to metal poisoning I'm sure I'll get a kick out of these replies.

Can I stick magnets to you?

That would be cool.

Looks like mercury caused the mass extinction 250 million years ago. GOP responds that's false, the Mercury Council has proven that it's good for you (except when it's in CFL bulbs), and those mad hatters were just putting on an entertaining show for their customers

/gentlemen, start your engines

Clean coal.

One of those two words is a lie. Just ask balding West Virginia.

Could have been the bullet that caused his death, but maybe he was just standing in the wrong spot.