Fireweed Fears Hosed Down
Algal blooms are not as hazardous to human health as has been feared because most people are sensible enough to avoid them.
Although it contains a cocktail of 70 potentially harmful chemicals, the fireweed algae that blooms in the waters of Brisbane’s Moreton Bay does not cause serious health problems in humans.
A study by the National Research Centre for Environmental Toxicology (EnTox), part of UQ, has revealed fireweed grows in explosive bursts in warm water and sunlight and is most toxic at the peak of its spread and density.
Fireweed is blue-green algae called Lyngbya majuscula, which contains toxins that turn some marine animals off their food and can also cause rashes, itches, burns, tingles, blistering and breathing problems.
Despite summer blooms that have been recorded up to 40 square kilometres wide in Moreton Bay, the study found fireweed had not had a dramatic effect on recreational water users.
UQ PhD graduate Dr Nicholas Osborne, who spent several years researching fireweed, surveyed 1370 residents of bayside Bribie Island about their exposure to Moreton Bay waters.
About 35 percent of people reported at least one side-effect, with skin itching the most reported (23 percent) and fever, the least reported (less than one percent).
About three percent of people surveyed (29 people) reported severe skin symptoms, for which 12 consulted doctors.
“Even though it does have the potential to be a health hazard, it doesn’t appear to be one at the moment,” Dr Osborne said. “People don’t go swimming in clumps of weed. They tend to walk 50 metres up the beach and go where the weed isn’t especially if they are informed about the potentially toxic nature of this organism.”
Dr Osborne collected fireweed samples from eastern Moreton Bay, the north of nearby Deception Bay and Bribie Island and found tenfold differences in toxin concentrations in some samples that had been collected only metres apart.
“Having different toxins in different areas meant that there is some sort of regulation of toxin production going on,” he said. “If we can work out what factors affect this regulation, we have a good handle on predicting when Lyngbya will be toxic and when the public should be warned.”
Younger people were more likely to report skin, eye, fever and headache symptoms and females reported greater skin rashes possibly because their swimwear could more easily trap algae.
Dr Osborne said large Lyngbya blooms often disappeared after storms and that while strong sunlight helped the cyanobacterium grow, it might also reduce its toxicity once the weed washed onto beaches.
The fireweed discoveries were reported in Dr Osborne’s thesis: Investigation of the Toxicology and Public Health Aspects of the Marine Cyanobacterium, Lyngbya majuscula.
The research was funded under a joint grant from the Australian Research Council and Queensland Government of $217,061 as a response to several reports of fireweed burns suffered by swimmers throughout South East Queensland waterways.