THE OCEAN AND CLIMATE

THE  OCEAN  AND  CLIMATE

The evolution of photosynthesis remade the Archaean Earth. Before photosynthesis, the air and oceans were anoxic. Now the air is a biological construction, a fifth of which is free molecular oxygen, and the ocean can sustain animal life even in the depths. The evolution, first of not producing oxygen] and then of oxygenic [producing oxygen] photosynthesis, sharply increased the productivity of the biosphere. Oxygenic photosynthesis sustains free oxygen in the atmosphere. In the oceans, the beneficiaries of the first photosynthetic prokaryotes [bacteria and archaea] today range from cyanobacterial and algal plankton to large kelp. Wearing plants as landsuits, from tiny mosses to giant redwoods, cyanobacteria as chloroplasts have occupied the land. The oxygen emitted has allowed the evolution of animal life, to browse the plants and, in turn, to respire the CO₂ that sustains photosynthesis.

Earth is totally different from what it would be if it had no ocean. The ocean, and life in the ocean, have "constructed the planet." The ocean is an important part of the Earth System, and it influences the transformation of energy and materials important to the climate system. On the most basic level, the ocean has shaped our atmosphere. Over millions of years, the concentration of gases in the atmosphere is determined by life. If life did not exist, especially life in the ocean, earth would be very different. On a deeper level, oceanic microbes irreversibly altered the geochemistry of earth and the biogeochemical cycles of H, C, N, O and S.
Please note, there is only one ocean with many named parts. The largest parts are the Atlantic, Indian, and Pacific Oceans. Earth would be much different if there were several different disconnected oceans..