Cloral
08-18-2008, 01:37 PM
I was watching Nova yesterday and they had a piece about a lake in New York that below a certain depth is toxic. The reason, it seems, is because the lake is narrow and deep. Thus, the lake surface cannot absorb oxygen from the atmosphere quickly enough to keep the water well-oxygenated. Thus the deeper lake waters tend to be anaerobic. Under such conditions normal life cannot survive. However, there is a class of bacteria that thrives in this condition. This bacteria produces hydrogen sulfide as a result of its metabolism process. Hydrogen sulfide is the gas that is responsible for the 'rotten eggs' smell, and in large quantities it can be fatal.
The scientist they were following in the piece was studying the lake because he theorizes that such conditions in wide scale led to the Permian Mass-Extinction. Studies of the Permian geologic boundary have shown that the oceans at that time were very poorly oxidized. This would have led to the lake-bottom conditions occurring across the entire ocean. And such a wide-scale release of hydrogen sulfide would have killed a majority of the life not just in the ocean, but on land as well.
How could such conditions arise in the oceans? Two words: global warming. Warmer air temperatures lead to increased stratification of the waters, reducing deep water mixing. Deeper waters are starved of their oxygen, and eventually become anaerobic. The bacteria blooms, and everything else dies.
The scientist they were following in the piece was studying the lake because he theorizes that such conditions in wide scale led to the Permian Mass-Extinction. Studies of the Permian geologic boundary have shown that the oceans at that time were very poorly oxidized. This would have led to the lake-bottom conditions occurring across the entire ocean. And such a wide-scale release of hydrogen sulfide would have killed a majority of the life not just in the ocean, but on land as well.
How could such conditions arise in the oceans? Two words: global warming. Warmer air temperatures lead to increased stratification of the waters, reducing deep water mixing. Deeper waters are starved of their oxygen, and eventually become anaerobic. The bacteria blooms, and everything else dies.