> others have made the argument that pollution from fertilizers, manure and other organic wastes, such as sewage, have placed the Earth’s oceans on the “edge of anoxia,” or a complete lack of oxygen.
This is nonsense, obviously. Would apply only for shallow bottom or fresh waters
Can you explain further, please? I don't doubt what you are saying, but don't know why it is "obvious". Is it, because the amount of sea water is so large, relative to the amount of 'pollution'?
The abstract of the paper linked in the article seems to support your statement, though.
"For the past several hundred million years, oxygen concentrations in Earth's atmosphere have been comparatively high[..]. Yet, the oceans seem never to have been far from anoxia (oxygen depletion)[..] OAEs seem to be promoted by warm climates[...] ocean oxygen concentrations are declining in the modern ocean [...] A full-scale OAE would take thousands of years to develop[...]"
(OAE = oceanic anoxic event)
https://www.science.org/doi/10.1126/science.aaj2321
So my layman summary of that particular study, would be, that the oceans have always been one the “edge of anoxia”, and although human activity could push it closer to that, there is no reason to believe that it could happen in our lifetime or that of our grand-grand children.
To start anoxia is a relative term. It depends on how much oxygen do you spent respect to how fast you replace it. Is also a buffered event, and the problem corrects itself automatically [1]. Therefore, things like "the edge of anoxia" have moving boundaries and are difficult to define
[1] When some area is lacking oxygen, marine life response migrating or is simply killed. The result is that more oxygen is available for the rest until reaching a new equilibrium.
The article provided is paywalled, so I can't really evaluate it here
Lets continue. If you put fertilizers into a flower, it will (try to use it to) grow. In the ocean is exactly the same. Marine life, evolved to feast or famine, will wake up and multiply like if the entire population of humpback whales is coming for they. The event is called "bloom" and is of major importance for humans.
Water will be filled with high concentrations of things that love to release oxygen. Bazillions of oxygen. Thus throwing fertilizer in the ocean equals to oxygen increase, not decrease... in principle.
Of course, biology is never so simple. You can have most life killed by lack of oxygen even while being submerged in a soup of oxygen producers because anoxia is a relative term. Life also breathes. And, unlike photosynthesis, breathing is done also at night. At the end of the night life can experience troubles to survive.
And there is the chemistry also. Stuff reacts chemically with the salts or organic matter suspended in the sea. This can release oxygen as by-product, remove oxygen and store it in some molecule, or remain neutral about it.
Chemistry can also affect oxygen producers. Too much fertilizer and your plant will die by thirst. In the sea the problem is reduced because your flower pot can decide to swim away or sink away.
This is nonsense, obviously. Would apply only for shallow bottom or fresh waters