[Campbell Biology P.1227] Based on the text and related concepts, if an algal bloom occurs in... | Practice Question

Based on the text and related concepts, if an algal bloom occurs in a lake and then the algae die, why would this lead to a reduction in the lake's oxygen levels?

  • A: The dead algae absorb oxygen directly from the water.
  • B: Decomposers break down the complex molecules in the dead algae using aerobic respiration, consuming oxygen.
  • C: The algal bloom itself consumed all available oxygen while alive.
  • D: The dead algae block sunlight, reducing photosynthesis by other aquatic plants.

Explanation

The text states that when algae from an algal bloom die, 'complex molecules in their bodies are broken down by decomposers using aerobic respiration.' Aerobic respiration consumes oxygen, leading to reduced oxygen levels in the lake.