Image via Anthony Rowland from the Facebook Victor Harbor Community Group
Following reports of dead sea life washing up along the southern coastline and surfers experiencing health issues after entering the water, the South Australian Government has released an official statement identifying the cause.
The Environment Protection Authority (EPA) has confirmed that Karenia mikimotoi, a species of microalgae, is behind the current bloom affecting the Fleurieu Peninsula. This particular species is known for its harmful effects on marine life and potential health impacts on humans, prompting several beach closures and ongoing monitoring by authorities.
Karenia mikimotoi poses a serious threat to both fish and invertebrates, often proving fatal by damaging fish gills. For humans, exposure to the algae—especially through surf and wind breaking it into particles—can lead to respiratory irritation, eye discomfort, skin rashes, and in some cases, gastrointestinal issues or flu-like symptoms. These effects typically subside once exposure ends or after washing off with clean, fresh water.
David Cunliffe, SA Health Principal Water Quality Adviser says, “In humans, exposure (including through breathing in algae particles broken up by the surf and wind) can cause general allergic-type responses, including respiratory and eye irritation or skin rashes in some people, while ingestion could cause stomach upsets or flu-like symptoms.
“These symptoms disappear when the exposure stops or following washing in clean water. There are no long-term effects.
“In general, people should avoid contact with discoloured fresh or marine water. If they do enter this water they should take care to wash in clean water afterwards.”
The potential danger to public health and marine life has led to the EPA issuing warnings and the closure of popular beaches such as Waitpinga Beach and Parsons Beach until conditions are deemed safe. The advisory signs have been placed along various council-run beaches, urging the community to adhere to these cautions.
The phenomenon of Karenia mikimotoi blooms is not unique to South Australian waters; it has been documented globally since the 1930s. Past outbreaks, similar to the recent one on the Fleurieu Peninsula, have occurred in international marine environments, including Japan and New Zealand, where they affected extensive marine life.
According to the EPA, the development of this bloom has been partly fuelled by an ongoing marine heatwave. The waters around Fleurieu Peninsula are currently registering temperatures approximately 2.5 degrees above the average, coupled with unusually calm conditions characterised by little wind and minor swell. These factors are believed to have contributed to the bloom’s emergence and persistence.
The impact of the microalgae has been noticeable from Cape Jervis to Encounter Bay, gathering attention and concern from the local population. Over the past week, the sightings and effects on the environment and local community have intensified calls for vigilance and caution.
Susan Close MP, Deputy Premier Minister for Climate, Environment and Water shared, “Now we know exactly what we are dealing with, I would encourage people to avoid the water and shoreline along the affected beaches.
“The EPA will continue to monitor the microalgae bloom and beaches will reopen as soon as it dissipates.
“If people do come into contact with the microalgae, please follow the health advice and wash it off with fresh water.
“With temperatures, including water temperatures, continuing to rise as part of climate change, we need to remain vigilant for these type of events and I thank everyone who took to the time to report the bloom to authorities.”
Residents and visitors in the affected areas are urged to report any unusual conditions or water sightings to Fishwatch on 1800 065 522 or the EPA on 1800 623 445, or by contacting [email protected]. This will assist in managing the current bloom and mitigating any potential future outbreaks.
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