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View all search resultsMass fish death in Lake Toba blamed on pollution, strong winds
Ternala explained that the bottom of Lake Toba is heavily polluted by leftover fish feed from floating fish farms. This waste has led to an accumulation of organic matter, which decomposes anaerobically without oxygen at the lakebed, releasing toxic compounds that can harm aquatic life.
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Members of the Medan Indonesian Christian University Students Movement (GMKI) in North Sumatra hold a street rally on July 26 in Medan to call on the local government to revoke the business permits of Lake Toba’s polluters. (JP/Apriadi Gunawan)
A
n environmental expert has linked the sudden murkiness of Lake Toba and the recent mass fish death in the popular North Sumatran crater lake to a combination of natural phenomena and chemical pollution.
Ternala Alexander Barus, a professor of mathematics and science at North Sumatra University (USU), said that strong winds blowing across the lake in recent days have stirred up sediment and debris from the lakebed, a phenomenon known as an upwelling, causing the normally clear waters to become murky.
“Water from the lakebed rose to the surface, carrying mud and harmful compounds that are toxic to fish, which led to the mass die-off,” he said on Thursday as reported by Kompas.com.
Read also: Indonesia on brink of losing Lake Toba’s Global Geopark status
Ternala explained that the bottom of Lake Toba is heavily polluted by leftover fish feed from floating fish farms. This waste has led to an accumulation of organic matter, which decomposes anaerobically, without oxygen, at the lakebed, releasing toxic compounds that can harm aquatic life.
Making matters worse, his analysis of a water sample taken from the lake on July 22 showed elevated levels of nitrogen and phosphorus, both exceeding thresholds considered safe for freshwater ecosystems.
He explained that the elevated levels of phosphorus and nitrogen in the lake are primarily caused by untreated household wastewater, which contains nutrient-rich substances that flow directly into the water without proper filtration.
