What's with the unpleasant smell in Karachi?

Karachi resident, especially near the coastal areas faces unpleasant odours on an annual basis.

Karachi's coastal areas are grappling with a strong, unpleasant odor following the recent monsoon rains and tidal surges.

This smell is attributed to the decay of marine plants, particularly phytoplankton. Mohammad Moazzam Khan, an adviser at the World Wide Fund (WWF) Pakistan, had earlier explained that the stench arises from rotting phytoplankton that washes ashore at the end of the monsoon season.

“These plants can change the sea's color to green and can be toxic, often leading to increased mortality rates among marine life,” Khan noted.

He specifically mentioned Noctiluca scintillans, commonly known as Sea Sparkle, which is part of the phytoplankton group.

When these organisms wash ashore and decompose, they emit a foul odour that can last for several hours or even days.

Khan further stated that the unpleasant smell results from the decomposition of phytoplankton, which proliferates underwater during the monsoon.

The planktonic dinoflagellate, frequently found along Pakistan’s coast, tends to form large blooms, particularly during pre-monsoon (April to May) and post-monsoon (September) periods.

Experts highlight the importance of phytoplankton in maintaining the Earth's oxygen supply, as they produce two-thirds of the planet's oxygen.

These microscopic plants are vital to the global food chain and essential for marine ecosystems.