Scientists have potentially identified a little-known algal species, Karenia cristata, as the cause of a significant algal bloom in South Australia. This research is currently undergoing academic peer review. The study indicates that Karenia cristata was the dominant species throughout most of the bloom's duration and is one of five Karenia species found in the area. Notably, it is the only species known to produce brevetoxins, which are the toxins responsible for the bloom.

Professor Shauna Murray from the University of Technology Sydney has been leading the research team. They began their investigation after observing large amounts of sea foam, marine life deaths, and acute health symptoms in people near Victor Harbor beaches in March. This species has not been previously recorded in Australian waters, although it has been spotted twice off the coast of South Africa and once near Newfoundland, Canada.

The research describes Karenia cristata as an "emerging international threat with unknown consequences in changing ocean conditions." Professor Murray noted that respiratory symptoms reported by surfers in March indicated the presence of a brevetoxin-producing species, in addition to Karenia mikimotoi, which was initially identified in the bloom. This was confirmed in early May when the South Australia Shellfish Quality Program detected brevetoxins in local waters.

Professor Murray emphasized the rapid pace of their findings, stating, "Typically, this type of research might take a few years to establish, and we did it in just months rather than years." The team collected multiple samples from 39 sites, revealing that Karenia blooms often consist of a mix of species. She explained that the dominant algae can change over time and by location, with Karenia cristata being the most prevalent during the bloom.

The origins of Karenia cristata in Australian waters remain unclear. Professor Murray mentioned that a lack of historical research makes it difficult to determine how or when the species arrived. She speculated that it may have been present all along, given its previous detections in distant locations like Canada and South Africa. "It's part of what we would call the hidden flora — the species that are present but not very abundant that we never really investigated," she said.

While little is known about Karenia cristata, Professor Murray noted that it seems to thrive in water temperatures between 14 to 18 degrees Celsius, similar to a previous bloom in South Africa. She observed that the species appeared to flourish in South Australia during the cooler months starting in May, but cautioned that further testing is necessary to understand the conditions that favor its growth.

Professor Murray stated that the algal bloom has been "badly misunderstood" and possibly misrepresented since its onset. She emphasized that identifying the additional Karenia species is just the beginning of their research. Ongoing monitoring will be essential, not only in South Australia but across the country, due to the potential human health impacts of brevetoxins.

The brevetoxins produced by Karenia cristata are similar to those produced by Karenia brevis, which frequently blooms off the coast of Florida. However, Professor Murray noted a key difference: the Australian variant does not produce one specific chemical form found in the U.S. species, known as BTX-1, but does produce other forms. She acknowledged that there has not been extensive research into the toxicity of these different chemical forms but expects them to be similar in their effects.