1. Water Blooms or Alga Bloom: Presence of large amounts of nutrients in waters also causes excessive growth of planktonic (free-floating) algae such as Microcystis, Oscillatoria, called an algal bloom imparts a distinct colour to the ater bodies. Algal bloomscause deterioration of the water quality and fish mortalitydue to deficiency of O2 in water. Some bloom-formingalgae are extremely toxic to human beings and animals.
2. Death of Fishes: Aphanizomenon and Microcystis are toxic for Gambusia and Crepis fish and die when they feed upon them.
3.Others: The green alga Cephaleuros virescens cuases red rust on the leaves of tea and C. coftèae causes redust on the leaves of coffee. Gonvaulax and Gvrnnodiniumare toxic for human. Gonyaulx releases a toxin tetrado toxin which enters in humans via fishes. It causes numbness and paralysis.
