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← GeographyWhich mechanism causes deep-water oxygen depletion in poorly mixed fjords with high organic matter input?
A)Advective nutrient upwelling
B)Microbial decomposition oxygen consumption✓
C)Thermohaline density stratification
D)Photochemical oxidation of sulfides
💡 Explanation
When fjords receive high organic matter, microbial decomposition consumes dissolved oxygen as a result of cellular respiration, especially in deep waters with limited mixing. Therefore oxygen depletion results, rather than upwelling, stratification, or photo-oxidation which require different hydrographic conditions and chemical compounds.
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