In the ancient oceans, stagnant depths harbored poison-belching bacteria that crippled life on Earth, leaving it vulnerable to a knockout punch from volcanic eruptions, according to a new study.
Three to four million years before the Permian-Triassic extinction, also known as the Great Dying, the seas were already becoming oxygen-starved and sour, said the study in the journal Earth and Planetary Science Letters.
Changqun Cao of the Chinese Academy of Sciences in Nanjing and a team of researchers studied rock samples drilled in central China from the late Permian and early Triassic periods. Rocks from the extinction itself date to 252.2 million years ago, and show several chemical signs of catastrophe.
The team found that a few of the compounds extend back millions of years before the main extinction event. Known as biomarkers, the chemicals are evidence that Chlorobium -- green sulfur bacteria -- were living in the oceans.
And Chlorobium produces gobs and gobs of hydrogen sulfide. If this holds up, we have yet another piece of the puzzle. The reason for the million + years before the PT extinction presence is that the Permian Oceans were stratified for loooong time prior. The proof - which may be in the paper - is that the bacteria greatly increased in amount just before the end...