What causes estuarine hypoxia and how do human activities exacerbate it?

• A. Increased salinity from seawater intrusion directly reduces dissolved oxygen.
• B. Ocean acidification increases oxygen production by phytoplankton.
• C. Nutrient run-off promotes algal blooms; decomposition consumes dissolved oxygen, and stratification limits mixing, exacerbated by pollution and warming.
• D. Overfishing removes oxygen-consuming species, reducing hypoxia likelihood.

Answer: (C)