How do algal blooms affect aquatic life?

Algal blooms significantly impact aquatic life mainly by blocking sunlight and depleting oxygen in the water. When algae grow rapidly, they create a dense layer on the water's surface, which prevents sunlight from reaching the aquatic plants and phytoplankton below. This lack of sunlight inhibits photosynthesis, ultimately affecting the growth and survival of these primary producers in the ecosystem.

Furthermore, when the algal bloom dies off, the decomposition process consumes a substantial amount of dissolved oxygen in the water. This can lead to hypoxic (low oxygen) or anoxic (no oxygen) conditions, which are detrimental to fish and other aquatic organisms that rely on sufficient oxygen levels to survive. The combination of reduced light availability and depleted oxygen levels creates an unhealthy environment for aquatic life, leading to fish kills and a decline in biodiversity.

In contrast, while some might think that algal blooms could provide food for fish, the types of algae involved in harmful algal blooms are often toxic or unsuitable for consumption, and the overall negative impacts greatly outweigh any potential benefits. Therefore, the consequences of algal blooms are far more harmful than beneficial to aquatic ecosystems.