• 2025-07-09

Algal bloom

Algal bloom

An algal bloom refers to the phenomenon of abnormal proliferation of algae or cyanobacteria (blue-green algae) in water bodies, often manifested through significant changes in water color (such as blue-green/brownish-yellow). The main cause of its formation is eutrophication of water bodies, particularly the excessive input of nutrients like nitrogen and phosphorus, leading to a sharp increase in algal biomass.

Dual ecological impact

■ Negative effects

Toxicity hazards

Toxic algae species (such as Microcystis, Gymnodinium) release hepatotoxins/neurotoxins

Threatening human drinking water safety and the survival of aquatic animals

Environmental stress

Blocking sunlight hinders underwater photosynthesis

Algal decomposition consumes oxygen, causing hypoxia in water bodies (dissolved oxygen < 2mg/L)

Forming dead fish zones or extinction of benthic organisms

■ Limited positive significance

Non-blooming algal proliferation constitutes the foundation of the aquatic food chain

Can serve as an early indicator signal for nutrient pollution in watersheds