Did a Rare Microbe Just Trigger Unprecedented Harmful Algal Blooms in Australia?

Did you know a single-celled microbe can quieten a massive coastal ecosystem? In 2025, an unprecedented ecological disaster struck South Australia, killing over a million marine creatures across a 20,000-square-kilometre area. The devastation lasted for over a year, affecting more than 600 species and causing human health warnings.

The Science Behind Harmful Algal Blooms

Scientists historically blamed one specific microbe for these toxic events. However, researchers analysing this disaster discovered that a rare, poorly understood microalga called Karenia cristata dominated the water.

To identify the killer, the team utilised:

• DNA metabarcoding to profile the microbial community
• Long-read sequencing to characterise the microalgal assemblage
• Liquid chromatography to isolate the specific toxins

Under laboratory conditions, assays on the isolated strain confirmed that K. cristata produces substantial amounts of brevetoxins. While it utilises a different chemical profile compared to its famous relatives, it remains highly lethal to marine life.

How This Changes Ocean Monitoring

This discovery suggests that toxic events may occur in unexpected regions as environmental factors shift. Wind and ocean currents likely entrained these cells coastward, concentrating the toxins. To protect global fisheries and coastal communities, researchers must now track this species worldwide.