Which outcome reduces marine primary productivity when coastal upwelling weakens during an El Niño event?

💡 Explanation

When upwelling weakens, the mechanism of nutrient transport from the deep ocean slows because the driving pressure gradient diminishes, leading to decreased nutrient concentration in surface water. Therefore, decreased nutrient availability occurs near the surface impacting photoplankton growth, rather than the other listed effects that are also associated with El Nino Southern Oscillation.

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