Karachi reeks as marine microorganism decays on coast

The stench that gripped many areas of the city from Tuesday night to Wednesday evening was caused by the decay of a type of marine plankton, Noctiluca scintillans, also known as sea sparkle.

This was stated by experts of the World Wide Fund for Nature-Pakistan (WWF-Pakistan) on Wednesday. WWF-Pakistan Technical Adviser Dr. Moazzam Khan said the sea movement in the post-monsoon season causes the microscopic organism to move to the coast where they ultimately die due to lack of nutrition and other reasons.

The microscopic organisms, which are technically classified as planktonic dinoflagellate, are commonly found along Pakistan’s coast and known to form large blooms, especially during the pre-monsoon season in April and May, and post-monsoon season in September.

WWF-Pakistan observers reported a large bloom of sea sparkle present in the northern part of the Arabian Sea during September, Dr. Khan said, adding that the end of the monsoon season with the accompanying changes in currents and wind patterns during the last few days caused the bloom to collapse on the coast.

“This resulted in the spread of a decaying seaweed smell in the city,” the WWF-Pakistan official said, adding that a similar foul smell had spread in Karachi on May 31, 2017 because of a similar collapse of Noctiluca scintillans bloom.

Responding to a query, Dr. Khan said the movement of the microorganism towards Karachi’s coast was not associated with the tropical cyclone ‘Luban’ in the Arabian Sea. He added that sea sparkle were reported on Pakistan’s coast on many occasions.

According to Dr. Khan, the bloom occurs in two forms, red-orange and green, and it sometimes also result in mortality of fish and shellfish. The current bloom was green, however, it did not cause mortality of fish or shellfish.

The WWF-Pakistan official said the bloom of Noctiluca scintillans normally occurs twice a year. He added that the change in currents in the post-monsoon season cause the microorganism to die, resulting in an atypical odour. “The smell is not harmful generally,” he maintained.