The Hindu Business Line : Sea scourge drifts southward; puts coastal residents in a tizzy

THE `red tide bloom' of toxic plankton that feeds on sewage, fertiliser and pet waste dumped into the sea invaded the Thiruvananthapuram shoreline on Friday, triggering a public health scare along the coastline.

More than 100 children from schools along the coast had to be given medication for nausea as the stench caused by the fish that had died after consuming the toxic plankton.

According to local residents, the stench existed from early morning and grew severe as the day progressed. Some schoolchildren attending the morning assembly collapsed and had to be taken to hospitals.

However, no emergency case has been reported. Officials of the Public Health Department visited the affected areas.

The red tide bloom was first reported in Kollam last week, causing panic in the coastal areas. The bloom is known to subside after four or five days.

Scientists at the Centre for Earth Sciences Studies (CESS) here have drawn a correlation between population growth and the aquatic scourge. Increased volumes of fertiliser, sewage and other biological waste pumped into the sea lead to the formation of a nutrient-rich mix, which is gobbled up by algae.

Giant blooms are known to pull oxygen from the water when they die and rot. Fish and other sea creatures can thus suffocate and die en masse.

The concentration of plankton gives seawater a distinct colour during a bloom. It is normally brownish red, as was found in the Kollam seas. But in Thiruvananthapuram, fishermen and coastal residents reported a greenish tinge in the seawater. A red tide bloom was earlier reported from the coastal areas of Thiruvananthapuram in 1997 and 1999.

A team of CESS scientists carried out several tests in the coastal areas in Kollam and found that the bloom was caused due to large quantities of sewage flushed out during the rainy season. The organism was identified as coclodeneum, a species belonging to the dinoflagellate group of marine plankton.

Blooms are known to cause in fish a burning sensation in the eyes and nose and a dry choking cough. When the bloom becomes severe, fish die from the neuro-toxic effects of the red tide that enters their bloodstream through the gills.

Red tide well below the `fish kill' level pose a serious problem to public heath through shellfish contamination. The studies also show that the presence of airborne toxins have an impact on the human respiratory system.

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