In short:
A toxic algal bloom linked with marine deaths across South Australia is “not far off” the size of Kangaroo Island, according to Environment Minister Susan Close.
Experts say the bloom is triggering unusual behaviour in marine wildlife, with the micro-algae being investigated as a possible cause of death for a shark that washed up on an Adelaide beach this week.
What’s next?
Ms Close says a “big change” in the weather is needed to break the bloom up.
A toxic algal bloom impacting multiple beaches across South Australia is nearly the size of Kangaroo Island, according to the state government.
Environment Minister Susan Close said the outbreak of Karenia mikimotoi, a type of micro-algae linked to the deaths of countless marine animals, has grown to an unprecedented scale.
“It is a larger bloom than we have ever seen before,” Ms Close said.
“It is not far off the size of Kangaroo Island and in some parts it’s as deep as 20 metres.
“We’re talking about a very large algal bloom with a significant impact on marine life.”
Kangaroo Island is Australia’s third largest island, measuring 4,405 square kilometres.
Beachgoers first sounded the alarm about the bloom back in March after thick foam and dead marine animals washed up on Waitpinga and Parsons beach on the Fleurieu Peninsula.
Multiple surfers reported feeling unwell at the time, with symptoms including coughing, sore eyes and blurry vision.
The algae is considered non-toxic to humans but can cause allergic reactions.
Since then, reports of dead marine life have spread to Kangaroo Island, Yorke Peninsula and beaches south of Adelaide.
‘Nothing we can do’
Ms Close said the outbreak was being driven by a marine heatwave coupled with still ocean conditions.
She said water temperatures were currently 2.5 degrees warmer than usual, likely due to climate change.
“The only thing that is going to break this algal bloom up is a change in the weather and starting to get strong westerly winds,”
Ms Close said.
“Normally we get that around the end of April – that hasn’t happened yet.
“We need a big change in weather to break this thing up; there is nothing we can do to precipitate this.”
According to the Department of Primary Industries and Regions (PIRSA), algal blooms of this size and nature are “rare” in South Australia, with the last outbreak recorded in Coffin Bay in 2014.
“Similar outbreaks around the world have generally lasted between a week to several months depending on wind, rain and ocean temperature fluctuations,” a PIRSA spokesperson said.
‘Unusual’ incidents
Concerns have been growing about the welfare of local marine life in the wake of numerous incidents, some of which have been described by experts as “unusual”.
On Monday, authorities removed a dead white shark which had washed up on Henley Beach.
Two other sharks were reported dead at Port Willunga and Port Moorowie in April, while a third was able to be returned to the waters near Ardrossan last week.
Ms Close said the researchers are working to determine the cause of death of the shark found at Henley with results due next week.
“We don’t know for sure if that was affected by Karenia mikimotoi, although I believe that is a reasonable assumption that that is likely to have been the case given then the presentation of the animal,” she said.
“Having a great white go up on the coast of Adelaide on a very popular beach, that is distressing to people.”
Last week, a woman was barbed by an eagle ray while surveying the impact the algae was having on the ecosystem along the Yorke Peninsula.
Marine biologist Dr Mike Bossley, who was leading the expedition, said he observed stingrays being more active and aggressive than normal, but it remains unclear how the algae can impact the behaviours of marine animals.
“Something has made these rays and sharks go a bit crazy and they’re just unpredictable at the moment,” Dr Bossley said.
“These microscopic algae can coat the gills of fish and it could be that they are basically being suffocated … that’s what’s causing them to act in strange ways.
“I would recommend people give careful thought to whether they go in the water where the algal bloom is happening … it’s quite dangerous.”
Ms Close said beachgoers should not enter the water if they believe algae is present.
“If you see that there is scum on the beach, if you see that there is discolouration in the water – stay away, don’t go in,” Ms Close said.
“And if you have been in, wash yourself down thoroughly.”
