Algal Bloom:

• An algal bloom or marine bloom or water bloom is a rapid increase in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments.
• Algal blooms are the result of an excess of nutrients (particularly phosphorus and nitrogen) into waters and higher concentrations of these nutrients in water cause increased growth of algae and green plants.

How Algal blooms are harmful?

• Algal blooms are a concern for the ecosystem as some species of algae produce neurotoxins. At the high cell concentrations reached during some blooms, these toxins may have severe biological impacts on wildlife.
• Algal blooms composed of phytoplankters known to naturally produce biotoxins are often called Harmful Algal Blooms, or HABs.
• It can also be harmful by causing anoxic conditions where oxygen is depleted from the water. Blooms can block light to organisms lower in the water column, or even clog or harm fish gills.