Red tide

• Red tide has recently occurred on the coast of Florida. It has been occurring since the 1800s in the Gulf of Mexico.
• Red tide is caused by a toxic algae species known as Karenia brevis. It occurs when the algae multiply in large numbers and form blooms, resulting in the water turning reddish-brown.
• The algae produce brevetoxins, which are fatal for aquatic life and capable of making humans sick.
• It could also block out the sunlight and deplete the water’s oxygen levels. It was responsible for the deaths of over 2,000 tonnes of marine life between 2017 and 2018.

Timing of Red tide

• It occurs during summer and spring when the sunshine is apt.
• During this time, the water is warm and slow-moving.
• Also, the water is rich in nutrients as the rivers are free from ice and are adding more nutrients to the sea. The algal bloom is always more in the areas where there is a mixture of brackish and marine water.

In India

• The west coast of India is more prone to algal bloom.
  • Algae like diatoms, cyanobacteria, haptophytes, and raphiphytes cause an algal bloom in India.
• Most of the algal blooms occur during the retreat of southwest monsoon and also during the pre-monsoon period.
• Although east coast has more nutrients than the west coast as it has more number of rivers draining.
• But the temperature and water current are more suitable on the west coast. So more algal blooms occur on the west coast of India.