Reek badly disturbed mainly District South and West of the city through the day with complaints from citizens as people remained unsure of the stench prevailed over the coastal parts whether what was affecting the atmosphere.
According to the WWF-Pakistan, stench was from collapsing of phytoplankton bloom caused by Noctiluca - an oceanic species also called sea sparkle. It said that planktonic dinoflagellate is commonly found along Pakistan's coast and known to form large blooms, especially during the pre-monsoon (April-May) and post-monsoon (September).
It said that a large bloom of the phytoplankton was witnessed in the Northern Arabian Sea during September, which its observers reported from fishing vessels. With the end of monsoon season, changes in the currents and wind patterns during the last few days have resulted in beaching and collapsing of the bloom. "This resulted in the spread of a decaying seaweed smell in the city," it added.
A similar foul smell spread in Karachi on 31 May 2017 because of a similar collapse of bloom of Noctiluca scintillas. The mass bloom of this small free floating organism was reported from the Arabian Sea including Pakistan's coast. Noctiluca scintillans blooms, commonly known as sea sparkle, have been reported from Pakistan's coast on many occasions. "They occur in two forms, i.e. orange (or red) and green, which sometimes result in the mortality of fish and shellfish. During the current year the mass scale green bloom occurred but no mortality of fish or shellfish has been reported from Pakistan so far," the WWF-Pakistan said.
Technical Advisor (Marine Fisheries), WWF-Pakistan, Muhammad Moazzam Khan said that the bloom of Noctiluca scintillans occurs at least twice a year. However, in some years, the intensity of the bloom grows 'substantially' and results in fish mortality in some cases.