At least 20 endangered Ganges river dolphins still survive in Bangladesh’s extremely polluted Buriganga River, a 12-month study found, reports contributor Md Jahidul Islam for Mongabay. Skirting the southern edge of the country’s capital, Dhaka, the 29-kilometer (18-mile) river is recognized as one of the most contaminated urban waterways globally. Researchers surveyed a 27-km (16.7-mi) stretch of the river between September 2023 and August 2024, observing Ganges river dolphins (Platanista gangetica) in 10 out of the 12 survey months. Group sizes averaged about four individuals, with calves accounting for nearly 16% of sightings, signaling active reproduction despite severe ecological degradation. “The Buriganga is not a usual place for dolphins, where native fishes have largely vanished,” study co-author and researcher Md. Aminur Rahman told Mongabay. “When we found [the dolphins], we were amazed at how it was possible. Because the river is not livable for fish.” A 2025 study on the Buriganga River’s water pollution showed that it absorbs untreated industrial effluent from tanneries, textile dyeing plants, battery factories, and municipal sewage. Levels of toxic heavy metals, including lead, chromium, and cadmium, routinely exceed World Health Organization safety limits, driving dissolved oxygen levels near zero during the dry season, the study reads. While native fish species have collapsed, pollution-tolerant invasive suckermouth catfish (Hypostomus plecostomus), native to South America, have multiplied rapidly, Rahman said. Mohammad Abdul Aziz, study co-author and zoology professor at Jahangirnagar University in Dhaka, told Mongabay that the dolphins have likely adapted their diet to survive on these invasive…This article was originally published on Mongabay

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