Which risk increases when increased freshwater runoff disrupts the density gradient within a subtropical gyre?

💡 Explanation

When freshwater runoff increases, salinity decreases, weakening the density gradient because density differences drive vertical mixing essential for nutrient resupply to the photic zone and hence carbon sequestration. Therefore, decreased carbon sequestration results, rather than altered upwelling, hydrothermal vents, or mangrove expansion which require geologic or coastal processes.

• Which phenomenon increases due to the Ekman transport effect on coastal upwelling regions during offshore winds?
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