The phenomenon, which is common during the monsoon months, is believed to be caused when untreated sewage mixes with sea water.
During a similar occurrence earlier, Pravakar Mishra, Scientist, Integrated Coastal and Marine Area Management (ICMAM) Project Directorate, which has been regularly monitoring the city’s coastline and has inspected the situation, said, “This is occurring on the surf nearest to the Cooum river mouth. It is a toxin producing bloom induced by high nutrients brought by sewage rich in phosphate coming from detergents. Phaeocystis sp. usually grows and forms bloom after the bloom of diatoms. It requires the presence of nutrients such as nitrogen, mainly in the form of nitrate ammonium and phosphate. They are not preferred by zooplankton such as copepods; ultimately a large fraction of their cells get mineralised at the surface water and releases CO2 in the process, which creates foam on the beaches. This is a regular phenomenon after a good spell of rain, with a conducive temperature and availability of nutrients for the bloom to be induced.”
Apart from being harmful to bathers, causing skin allergies, experts said that the bloom could also impact the marine eco-system, warning the fishermen to not fish in these contaminated zones.
A marine biologist, speaking on condition of anonymity, had said earlier, “The foam formation is due to bioturbation, where bigger and denser particles from sewage churn and create a foam. This can lead to sudden death in fish, hampering the entire eco-system. In some cases, the fish don’t die but the toxins are biomagnified and will enter the food chain and cause issues such as shell-fish poisoning.”