Toxic algae bloom off South Australia devastates marine life, tourism

A toxic algae blooms onto the beach near where a dead dolphin was found at Carrickalinga Beach on July 13, 2025 near Adelaide, Australia. (Photo by Tracey Nearmy/Getty Images)

SYDNEY -- A massive outbreak of toxic algae off South Australia, which has devastated hundreds of species of marine life and disrupted local tourism and fishing, is a “natural disaster,” state Premier Peter Malinauskas said on Tuesday.

The algal bloom, first detected in March, spans an area 4,500 square km (1,737 square miles) in size and has been aggravated by rising ocean temperatures, according to environment officials.

“There are over 400 different species of marine life that have been killed off or have had deaths as a result of this algal bloom,” Malinauskas told national broadcaster ABC’s News Breakfast program.

“This is a natural disaster and should be acknowledged as such.”

Malinauskas announced a A$14 million (US$9.11 million) support package to tackle the outbreak, matching a package by the federal government. The combined A$28 million would assist with clean-up efforts, research, and business support.

The toxic bloom has been caused by overgrowth of the Karenia mikimotoi algal species, which affects fish gills and sucks oxygen out of the water as it decomposes, the state’s environment department said.

Contributing to its growth was a marine heatwave that started in 2024, when sea temperatures were about 2.5 C (36.5 F) warmer than usual.

The bloom has impacted tourism and forced oyster and mussel farms to temporarily shut due to a waterborne toxin caused by the algae, local media said.

Over 13,850 dead animals, including sharks, rays and invertebrates, have been recorded by the public on the iNaturalist app.

Federal Environment Minister Murray Watt said on Monday the algal bloom was a “very serious environmental event,” but stopped short of declaring it a national disaster, which would allow for greater federal support.

(US$1 = 1.5363 Australian dollars)

(Reporting by Christine Chen in Sydney; Editing by Bernadette Baum)