Karachi, the southern coastal city of Pakistan, is up against another bout of this noxious smell in Karachi that has once again gripped the coastal strip of the city. This disturbing phenomenon, mainly due to decaying water plants called phytoplankton, usually occurs as an environmental condition acts up. This case has alarmed both the residents and environmental scientists; therefore, the ecological aspects of this natural occurrence are once again coming into discussion.
The noxious smell over Karachi was first noticed on September 5, after the last rains of the monsoon season, and returned with a vengeance. This year, the noxious odor coincided with a recent heat wave when very hot dry weather gripped the entire city, which was further fueled by wind blowing from Balochistan. Matters worsened on Monday night as dark skies and shifting winds helped spread the stench all over the city.
Muhammad Moazzam Khan said that, in Karachi, this smell is caused by the decomposition of phytoplankton. He added that the smell was caused by decaying phytoplankton. These microscopic aquatic organisms, generally invisible to the naked eye, multiply in colossal numbers underwater, mainly during the months of the monsoon. When they die or start decomposing, they give off a stench, which may be carried elsewhere by shifting winds before it is dispersed.
Phytoplankton, though not at center stage with other components on the planet, is, however playing an indispensable role in the entire system of the Earth. As they are known to produce nearly two-thirds of the world’s oxygen, it is very common to call them the “lungs” of the Earth. Not only do they thrive in the salty waters of the ocean, but they also thrive in rivers and wetlands. Some species are small, but large numbers make the blooms spectacularly visible, sometimes making patches of green stand out on the surface of the water.
These marine plants produce their food through photosynthesis by using sunlight and water, with oxygen being the by-product of this process. Given the very high output of oxygen they make in the food chain globally, such plant life sustains marine life in its oceans and keeps the ecological balance intact; however, the fresh stench of waves from Karachi harbor reflects the vulnerability of the equilibrium between natural processes and urban systems.
Among the bloom contributors, Khan identified Noctiluca scintillans commonly referred to as Sea Sparkle as one of those responsible for the offending smell. Noctiluca is a phytoplankton species that could tint the sea to a bright green and may even be toxic, thereby causing very high mortality rates among the sea creatures. The decomposition of these types of organisms can cause persistent odors that last for hours or even days after they are washed up on the shores, which discomforts nearby residents.
Ideal growth conditions for the phytoplankton often occur during monsoon season. During these periods, blooms can become enormous when waters, rich in nutrients are brought to the surface. This is especially true along Pakistan’s shoreline at two critical times: before the onset of monsoon rains in April and May, and after the close of monsoon season in September. Such periodicities remind us of a need to continue and intensify research and monitoring of the local consequences of phytoplankton dynamics.
Experts do indicate that maintaining an appropriate balance between mankind and nature can help prevent such events or phenomena in the future. Improvement of environmental conditions through observation of water quality could help in overcoming the problems that phytoplankton blooms present in its aftermath. Educating the public about these organisms may also help increase esteem for the importance of such microorganisms in the overall ecosystem.
Karachi’s latest bout of unpleasant smell is a reminder that nothing is ever separate and different from the others, but there is always a connection between human activity and the workings of nature. From a human or environmental perspective, knowing about these dynamics is important while trying to live through the everyday discomforting aspects of a coastal city meant to be influenced by nature’s tidal ebbs and flows. Dealing with this foul smell in Karachi will therefore mean collaboration between the government and the community to provide a healthier urban environment for all.
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