Carbon pollution is not the only man-made problem for Earth's oceans. Coastal pollution from runoff, often containing fertilizers, pesticides and other waste products (sewage) are also hastening the collapse of Earth’s oceanic oxygen cycle. Oxygen-free “dead zones” in Earth’s oceans are appearing and expanding at an alarming rate. Disruptions in the oceans’ oxygen cycle are the single-most significant and direct consequence of global industrialization.
Humans and most other land and marine animals breathe oxygen, and complex life as we know it cannot survive without it. It look more than four billion years for oceanic photosynthesis to release sufficient quantities of oxygen for terrestrial life to evolve. Life on Earth depends upon a delicate balance between the atmosphere and oceans. Ocean water absorbs most of the heat Earth receives from the Sun, and the relationship between ocean currents and atmospheric chemistry shapes the global climate.