The great mystery shrouding early life on Earth is that the first photosynthetic organisms able to produce oxygen – cyanobacteria evolved about 2.7 bln years ago, yet the concentration of oxygen remained low for next few hundred millions of years. Now the researchers from University of Alberta, Canada have proposed a solution for this apparent mystery. According to their model the cause may be of geological and not biological nature. They have analyzed the ratio of nickel to iron and have found that about 2.5 bln years ago there was a dramatic decrease in concentration of nickel. This element is an essential nutrient for methanogenic bacteria. The high methane concentration in the atmosphere was keeping oxygen level in check. The relatively sudden change in nickel availability caused a starvation of methanogenes and allowed the oxygen buildup, that further hindered growth of anoxygenic organisms.
The scientists propose that a primary cause behind sudden nickel decrease was cooling of Earth mantle that caused changes in composition of magma flowing out of the volcanoes in such a way that it had less nickel. This was followed by a decease in concentration of this element in the seawater and put a sudden blow (in geological terms) to the well being of the methanogenes.
The cool thing about the story is an Earth Mantle, but joking aside the fact that as a biologist I would never thing about such a far fetched thing as an influence of magma's temperature on life of some bacteria. This is awesome - good job geologists.