Unpleasant odour returns to city

A foul odour has once again spread across Karachi, particularly in the coastal areas, due to the decomposition of aquatic plants called phytoplankton. This phenomenon, linked to changing wind patterns, occurs every year.

The unusual stench, first noticed after the end of monsoon rains on September 5, has returned. During the recent heatwave, hot and dry weather prevailed in the city, accompanied by winds from Balochistan. However, cloudy skies and shifting wind directions on Monday night contributed to the odour being detected across various parts of the city.

According to WWF technical advisor Muhammad Moazzam Khan, the smell emanates from decomposing phytoplankton. These microscopic aquatic plants grow underwater in large quantities each year, and when they die or decay, they produce a foul odor. Khan explained that this situation typically occurs immediately after the monsoon season or when wind patterns change, with the stench carried across different areas by the wind before gradually dissipating.

Experts note that phytoplankton play a crucial role in the Earth's ecosystem, functioning as the planet's "lungs." These microorganisms produce a significant portion of the oxygen on Earth-up to two-thirds of the global supply. Found not only in salty ocean waters but also in rivers and wetlands, phytoplankton are so small that they are often invisible to the naked eye. However, when present in large numbers, they appear as patches of greenery on the water's surface.

Phytoplankton generates its own food through photosynthesis, using sunlight and water, and release oxygen as a by-product. Their role as oxygen producers makes them vital to the global food chain and essential to maintaining the Earth's ecological balance.