KARACHI: A foul smell reported from various parts of the city on May 31 and particularly felt in the city’s South, East and Central districts along the coastal belt was linked to a marine species’ decaying bloom, the World Wide Fund for Nature-Pakistan reported on Friday.

According to the organisation, the green bloom along Pakistan’s coast started appearing in February this year and continued till late May with a peak in March and April. In some areas, the seawater even turned into something resembling green soup.

The species was identified as planktonic dinoflagellate called Noctiluca scintillans, commonly known as sea sparkle, a marine organism which emits their own light when disturbed.

“It’s the first time that the bloom’s decaying caused so much smell that people took notice of it,” said Mohammad Moazzam Khan associated with WWF-P as its technical adviser on marine fisheries.

“A number of fishermen have reported discoloration of water and presence of this massive bloom floating in patches in the Arabian Sea since February this year. Now, the bloom is in its dying stage and stinking,” he explained.

The bloom had also hit the Oman coast and reportedly caused mortalities of pelagic shrimps along with some fishes there. However, there were no reports of mortalities of marine species in Pakistan so far.

Blooms of Noctiluca scintillans, he pointed out, had been reported from Pakistan’s coast many times.

“Usually, sea sparkle bloom occurs twice a year and in two forms, orange (or red) and green, which sometimes results in mortality of fish and shellfish, if the bloom is toxic,” he said.

Last year in October-November, the bloom caused fish mortalities in large numbers in Gwadar but the incident went unnoticed, he said, adding that the reasons which led to the bloom were still unexplored.

According to him, a reversal of current and wind patterns under the influence of the southwest monsoon in late May has resulted in the decay of the bloom, which caused the atypical stench in the coastal areas of Karachi.

“The frequency of such blooms is increasing in Pakistan which may be attributed to climate change or anthropogenic factors like pollution. There is definitely a need for research in this field,” senior director WWF-P Rab Nawaz added.

Plant or animal?

According to the information available on the website Ecomare, sea sparkle is a relatively large one-celled dinoflagellate, often referred to as algae. However, because it has many animal traits, there is much discussion whether this organism is a plant or an animal.

“It has no chlorophyll to produce food with the help of sunlight and therefore consumes other organisms, such as phytoplankton, zooplankton, bacteria and fish eggs.

“Sea sparkle doesn’t just eat other organisms. It engulfs them, allowing them to live further inside its membrane. Although consumed, the algae cells continue to live and split into new algae within the sea sparkle until they are finally consumed. Under the microscope, the algae appear as green flecks,” the website says.

Published in Dawn, June 3rd, 2017