UPSC 2025: 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?

Rain forests account for a much smaller share of global oxygen production than oceans, so Statement I is incorrect. Marine phytoplankton and photosynthetic bacteria are estimated to generate roughly half of Earth’s atmospheric oxygen, validating Statement II. Surface water at full saturation holds only ~8–10 mg O₂ /L, far lower than the ~210 mg O₂ /L (≈21 % by volume) present in atmospheric air, therefore Statement III is false. Hence only Statement II is correct. ([science.nasa.gov](https://science.nasa.gov/earth/earth-observatory/breathing-life-into-the-ocean-150656?utm_source=openai))