Mass fish death in Malaysia caused by algal bloom, not Fukushima wastewater

"Penang's sea after Japan released nuclear wastewater," reads simplified Chinese sticker text on a video shared on TikTok here on September 8, 2023.

"Penang Malaysia," reads sticker text above the video. "Don't dare to eat seafood anymore".

The one-minute, 29-second clip features a Chinese-language news report from Malaysian state broadcaster RTM about dead fish in Penang's northern Teluk Bahang area.

The anchor says worried residents reported the colour of seawater around the area had changed.

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Screenshot of the false post, taken September 25, 2023

The claim circulated shortly after Japan began the gradual discharge of treated wastewater from its crippled Fukushima nuclear plant on August 24, 2023, as part of a process deemed safe by the country's marine authorities as well as the UN atomic watchdog IAEA.

The move has drawn heavy backlash from other countries in the region, further inflamed by misinformation circulating on social media.

The video was also shared alongside a similar false claim elsewhere on TikTok here and here, and on Facebook, where it has racked up more than 650,000 views.

'Algae explosion'

However, the posts misrepresent the RTM news bulletin, originally uploaded on the organisation's official Facebook page here on August 28, 2023 (archived link).

The report is captioned: "Seawater changes colour, thousands of fish die in waters off Penang's Teluk Bahang.

"Recently, Teluk Bahang has seen a phenomena of thousands of dead fish floating in the sea, raising concerns among local residents.

"A local tour guide said this has never happened in the area before, and it is obvious that the colour of the seawater has changed, so he hoped authorities can pay attention and find a solution."

The newscaster repeats the same details throughout the report and does not mention Fukushima.

In a Facebook post on August 31, 2023, the Penang Fisheries Department said it investigated the incident and found the fish were suffocated by an explosion of algae which had lowered the oxygen content of the water (archived link).

Part of the agency's Malay-language statement reads: "The preliminary results of the analysis carried out by the Batu Maung Fisheries Research Institute to identify the 'Red Water' present in the waters of Teluk Bahang found that the algae is a non-toxic type of Noctiluca scintillans species and is not dangerous to humans.

"However, the density of phytoplankton cells is very high which is as much as 1-5 million cells/liter which confirms an algae explosion in these waters.

"The high density of phytoplankton cells can cause the death of fish, especially fish in cages due to a decrease in dissolved oxygen and algae have also covered the gills and caused the fish to not get oxygen."

Professor Dr Aileen Tan, director at the Centre for Marine and Coastal Studies at Universiti Sains Malaysia, told AFP available data indicates the incident in Penang was caused by a bloom in algae (archived link).

"The fish kills are caused by deoxygenation. It has nothing to do with Fukushima at this point," she said on September 13, 2023.

AFP has debunked similar claims about masses of dead fish since the Fukushima wastewater discharge here, here and here.