How does algae growth deplete oxygen levels?

Question

How does algae growth deplete oxygen levels?

Answer 1

Algae on the surface blocks the sun from algae that lives in deeper water. This increase the oxygen at the surface and reduces the oxygen in the deeper water.

Also the dead algae sinks and is decomposed by bacteria. These decomposers deplete the oxygen in the deep water.

Answer 2

Algae, like all plants, produce carbon dioxide during photosynthesis.

After a while, if unchecked growth of the algae occurs, the amount of oxygen in the water would decrease because of the rising levels of the CO2.

Eventually, it could kill off the fish and other aquatic life that need the oxygen for survival.