The Mystery of Digha's Yellowish-Brown Waves

The coastal waters near Digha have been experiencing something unusual. A peculiar bloom has been showing up around the same time each year. This bloom is not your typical seaweed or plant growth. It's a type of algae called Phaeocystis. These blooms are not good news. They can mess up the local ecosystem in a big way. The first sighting of this bloom was back in early December 2022. It covered a large area, about 150 square kilometers, near Talsari Beach. Guess what? It came back the following December. This suggests that these blooms might be a regular thing during the Northeast Monsoon season. To figure out what's going on, researchers collected samples from the Digha coast over two years. They found that the Phaeocystis colonies are round and have a yellowish-brown color. The number of these colonies varied a lot, from none at all to a whopping 652 colonies per liter of water.

The researchers broke down the bloom into four phases: initial, peak, decline, and late. They also measured the size of the colonies and the number of cells in each colony. The size ranged from about 1. 22 mm to 14. 22 mm, and the cell count varied from 1. 8 to 450, 000 cells per colony. So, what's causing these blooms? The study found that temperature, salinity, and nitrate levels are the key factors. Temperature is the big boss here, accounting for most of the changes in the bloom. During December, the cool, dry winds from the northeast drop the temperature below 24°C. At the same time, freshwater flowing into the coast changes the environment, making it rich in nitrate and silicate. This combo seems to trigger the Phaeocystis bloom. The return of these blooms is a big deal. It shows that more research is needed to understand their impact and how to deal with them. The Northeast Monsoon season brings unique conditions that might be fueling these blooms. Understanding these factors could help in predicting and managing future outbreaks.

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