A massive surge of urban pollution triggered by a major deluge across Istanbul and restricted water circulation caused by pontoon bridges has led to visible discoloration in the Golden Horn, a Turkish marine science expert has warned.
Professor Cem Gazioğlu, head of the Institute of Marine Sciences and Management at Istanbul University, said the surface water in the Golden Horn turned visibly murky, with a noticeable change in color, after intense storms last weekend that lasted into early March 30.
He explained that heavy rainfall increases surface runoff, carrying various pollutants and sediments from land into the estuary.
“The city received rainfall beyond its capacity. Materials dissolved and transported by rainwater reached the Golden Horn, causing turbidity and discoloration in the surface layer,” he said.
He warned that the impact is not merely visual.
Reduced water clarity prevents sunlight from penetrating deeper layers, placing additional stress on an already fragile ecosystem. Increasing frequency of extreme weather events, he added, could further weaken the ecosystem’s ability to recover.
Gazioğlu also pointed to structural barriers, particularly floating bridges, as a key factor worsening the situation.
“These structures limit natural water circulation, creating a more stagnant environment. Rainwater entering the system becomes trapped rather than dispersing,” he said.
He noted that while similar runoff occurs in streams across Istanbul, its effects are more pronounced in the Golden Horn due to its semi-enclosed nature. Unlike open seas, where pollutants dilute quickly, the restricted outflow in the Golden Horn allows murky water to persist longer.
“Beyond the floating bridge, we observe that the water gradually returns to normal as it disperses,” he added.
Gazioğlu emphasized that past rehabilitation efforts in the Golden Horn must be continuously maintained, as ecosystems are dynamic and require ongoing monitoring and intervention.
He also highlighted the growing impact of climate change, warning that extreme rainfall events are expected to become more frequent.
“Relying on distant institutions for intervention is no longer viable. Real-time, locally generated data must directly inform decision-making,” he said, proposing the use of unmanned oceanographic buoys and sensor systems along the Golden Horn to enable continuous monitoring, early warnings and rapid response.
“As we face more intense and sudden rainfall, infrastructure capacity, coastal vulnerability and ecosystem resilience must be reassessed. Our planning and management approaches need to evolve accordingly,” he said.
