Hypoxia

Dead zone: An area in aquatic ecosystems with severe hypoxia caused by excessive nutrient pollution, leading to the death of marine life.

Hypoxic zone: A region within a body of water where dissolved oxygen levels are below the threshold required for most aquatic organisms to survive.

Oxygen depletion: The process by which oxygen levels decrease in an ecosystem due to factors such as pollution, algal blooms, or increased respiration rates.