What is a red tide? Why is it harmful?

A red tide is a phenomenon of discoloration of the sea surface. It is a common name for harmful algal blooms occurring along coastal regions. 

Red tides produce harmful toxins, capable of causing fatalities to fish, shellfish, mammals and birds. In the case of humans, those with chronic respiratory illness are advised to avoid coastal regions affected by red tides.

For more relevant articles refer to the links given below:

• UPSC Environment and Ecology Questions
• Conservation of Biodiversity
• UPSC Environment and Ecology