With reference to the planet Earth, consider the following statements:
I. Rain forests produce more oxygen than that produced by oceans.
II. Marine phytoplankton and photosynthetic bacteria produce about 50% of world’s oxygen.
III. Well-oxygenated surface water contains several folds higher oxygen than that in atmospheric air.
Which of the statements given above is/are correct?
Answer:
(b)
Moderate
Application Based
Core Books/NCERT
Statement I is not correct. While tropical rainforests are vital to Earth’s carbon and water cycles, oceans—through marine phytoplankton and photosynthetic bacteria—are responsible for producing more oxygen globally than rainforests. Oceans are considered the largest source of atmospheric oxygen. Statement II is correct. It is a well-established scientific fact that marine phytoplankton, algae, and photosynthetic bacteria contribute to about 50% (or slightly more) of the global oxygen supply through photosynthesis. Statement III is not correct. Oxygen solubility in water is significantly lower than in air. Even well-oxygenated water contains only about 8–10 mg/L of dissolved oxygen, which is far less than the oxygen concentration in atmospheric air (~210,000 mg/L). So, water does not contain higher oxygen content than air.