Where did that oxygen come from originally?
Well it came from bacteria,from about 3.5 billion years ago, their fossils are found widely in precambrian areas.. Some of them are still with us today in what are called stromatalites. These stromatolites are found only in a few parts of the world One of the ironies is that they are only found in paces of such high salinity where other living things cannot exist. The stromatolites produced the oxYgen that permitted the other high level organisms to develop and exist.The irony,these organisms then ate them. The oxygen 02 and ozone 03 they produced protected those more advanced organizms and eventually us, from harmful UV solar radiation. The stromatolite bacteria use sunlight, the water and carbon dioxide to produce their food and their by-products are calcium carbonate (lime) and oxygen. The lime and a mucus are produced which form their distinctive layered shells.
Each time that there has been a major Extinction Level Event (ELE) their fossils show a marked increase until the higher organisms (mainly grazers) recovered and ate them again. There was no such thing as gratitude.
Another irony is that today two of the few places they exist are in Western Australia at Shark Bay, and in the Bahamas. Both relatively close to recent major oil spills. Perhaps they are lining up to save us again. This time from our own greed and stupidity.
Later of course the Diatoms and phytoplankton took on the task of producing the oxygen for us to breathe. Their reward ? The Chemical and Oil corporations do their very best to destroy them. What generosity!! The directors and shareholders of those corpoirations will undoubtedly edn up as the richest corpses in the morgue.I guess that will make them happy, however we cannot afford to let them take us with them.
When the diatoms die their incredibly beautiful microscopic bodies sink to the ocean floor and the irony their tiny bodies form, amongst other things ..............oil. Ironic?