KARACHI: The recent observations of sea discolouration and night-time bioluminescence by fishermen and coastal communities along Karachi and parts of the Balochistan coast are caused by naturally occurring, non-toxic bloom of Noctiluca scintillans, widely known as sea sparkle, and not linked to pollution, stated the World Wide Fund for Nature-Pakistan (WWF-P) on Wednesday.

The organisation also rejected concerns linking “these changes” with harmful algal blooms or eutrophication.

“We believe that the green discolouration of the ocean is caused by large, naturally occurring, non-toxic bloom of Noctiluca scintillans, a small, free-floating organism that may appear in red, orange, green, or even colourless forms.

“Along Pakistan’s coast, blooms are most often green or orange and can spread extensively depending on seasonal conditions. Although the organism itself is not green, the colour comes from its internal symbiont, Protoeuglena noctilucae, which enables it to photosynthesise and grow rapidly.

“Because Noctiluca is naturally bioluminescent, its presence creates the glittering glow reported at night,” it stated. Similar seasonal blooms had been documented across the coasts of Yemen, Oman, Iran, Pakistan and western India.

Published in Dawn, November 27th, 2025