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,

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.