Q. In the context of ecosystem productivity, marine upwelling zones are important as they increase the marine productivity by bringing the
- decomposer microorganisms to the surface.
- nutrients to the surface.
- bottom-dwelling organisms to the surface.
Which of the statements given above is/are correct? (UPSC Prelims 2011)
Answer:
2 only
Notes: Statement 1 is Incorrect: While decomposer microorganisms exist throughout the ocean, they are not the reason productivity increases. In fact, most decomposition happens at the bottom, and simply bringing the microbes up wouldn't trigger a massive growth of fish or plants.Statement 2 is Correct: This is the core mechanism. Deep ocean water is "nutrient-rich" because it contains the remains of dead organic matter (nitrates, phosphates, and silicates) that have settled at the bottom over time. When upwelling brings these nutrients into the euphotic zone (the sunlit upper layer), it triggers a massive bloom of phytoplankton.Statement 3 is Incorrect: "Bottom-dwelling" organisms (benthos) like crabs or deep-sea fish generally stay at the bottom and are not physically "swept up" to the surface by the rising water. The upwelling moves the water and its dissolved minerals, not the larger animals.