Trees release further oxygen than the ocean. Trees absorb carbon dioxide and release oxygen through the process of photosynthesis. A mature tree can produce as important as 260 pounds of oxygen per time. On the other hand, while the ocean produces oxygen, it also consumes it through respiration by marine life and other processes. The total quantum of oxygen produced by the ocean is much lesser than that produced by trees, but it's still consumed at a faster rate, making the net oxygen release from the ocean much lower than that of trees.