Karachi residents woke up to a strong and unusual smell on Wednesday morning. Many people near the coast reported a fishy odour in the air. So, What’s behind the foul smell in Karachi today? Experts say decaying microscopic marine algae are a major reason. Weather conditions are also helping spread the smell across the city.
Decaying marine algae linked to the smell
Muhammad Moazzam Khan, a technical adviser on marine resources at WWF-Pakistan, explained the possible cause. He said microscopic marine algae called phytoplankton are breaking down in the sea. This natural process can produce a strong and unpleasant smell. Phytoplankton are common in the upper layers of the sea. They grow in large numbers during the monsoon season. As the regional monsoon system ends around mid-September, sea conditions begin to change. These changes can lead to the decay of phytoplankton. The organisms are too small to see without special equipment. However, their decomposition can affect the smell around coastal areas.
Khan said Karachi experienced a similar situation in 2024. He added that the smell could disappear within a few days.
Weather conditions are also playing a role
The smell is not linked to marine activity alone. Weather conditions are also affecting how it moves through Karachi. Pakistan Meteorological Department spokesperson Anjum Nazir Zaigham highlighted the role of wind conditions. Climate change expert Fatima Yamin also pointed to a low-pressure area near India’s Jamnagar coast.
According to Yamin, the weather system was influencing wind movement around Karachi. The winds were carrying polluted air around the city. She said the combination of smog and weather conditions was helping the smell spread across different areas. Zaigham also mentioned south-easterly winds and the presence of smog. He said conditions could improve by the evening as the sea breeze develops.
Karachi has seen a similar smell before
This is not the first time Karachi has experienced such an odour. A similar smell was reported across several parts of the city in October 2024. Clifton, DHA, PECHS, Korangi, Orangi and Saddar were among the affected areas. Residents in North Nazimabad and Federal B Area also reported the smell at that time.
Experts previously linked the phenomenon to natural marine processes. Weather and air conditions also influenced how strongly the odour was noticed.
Should Karachi residents be concerned?
The current reports point to a natural marine process combined with weather conditions. There is no indication that the smell itself comes from a single pollution source. However, prolonged exposure to poor air conditions can cause discomfort for some people. An ecologist previously noted that dusty winds combined with the smell could affect people with sinus problems. At the time, there was no concrete evidence of wider health effects.
Residents can continue monitoring official weather and environmental updates. The smell is expected to reduce as weather conditions change.
What is causing the smell?
In short, the main explanation is decaying phytoplankton in coastal waters. Changing sea conditions after the monsoon are contributing to the process. Wind direction, smog and a nearby low-pressure system are also helping carry the odour. Experts expect the smell to ease as the weather changes and sea breezes return.
Read more about the latest Karachi news, weather updates, and environmental developments.