Definitely not. About 50% of the oxygen produced by photosynthesis is terrestrial, the rest is from the oceans (mainly phytoplankton). Trees are one source, but a bigger one is ocean algae (aka seaweed) and ocean phytoplankton. Together sea-plants generate about half the world’s oxygen.

The hypoxemic type of hypoxia is due to one of two mechanisms: (1) a decrease in the amount of breathable oxygen—often encountered in pilots, mountain climbers, and people living at high altitudes—due to reduced barometric pressure (see altitude sickness) or (2) cardiopulmonary failure in which the lungs are unable to …

The primary cause of oxygen depletion in a water body is from excessive algae and phytoplankton growth driven by high levels of phosphorus and nitrogen. During the nighttime hours, these photosynthetic organisms consume oxygen through respiration when engaging in active photosynthesis.

Ocean warming-driven deoxygenation: Warmer ocean water holds less oxygen and is more buoyant than cooler water. This leads to reduced mixing of oxygenated water near the surface with deeper waters, which naturally contain less oxygen.

Among the planets, Earth is unique for its oxygen-rich atmosphere. Part of the reason for this is that oxygen binds easily with other elements. With carbon to produce the carbon dioxide seen in the thick air of Venus, or with iron to form the rusty soil of Mars.

In the process of photosynthesis, phytoplankton release oxygen into the water. Half of the world’s oxygen is produced via phytoplankton photosynthesis. The other half is produced via photosynthesis on land by trees, shrubs, grasses, and other plants.

manchineel tree

Hippomane mancinella

Commonly known as deadly nightshade, belladonna, devil’s cherry, and dwale. One of the most toxic plants found in the Western Hemisphere, all parts of the plant contain tropane alkaloids – as do those of its equally deadly sister species A. baetica, A. pallidiflora and A.