Report Identifies Multiple Factors in South Australia's Catastrophic Algal Bloom

After more than 18 months of uncertainty surrounding South Australia's most catastrophic algal bloom crisis, a long-awaited report has been released by the SA government shedding light on the environmental conditions that fuelled the marine event.

The report has concluded that floodwater, a coastal upwelling and a marine heatwave all contributed to the conditions that led to the devastating event, but that there was no "single trigger".

The preliminary investigation was conducted by the South Australian Research and Development Institute (SARDI) into potential drivers of the bloom, and its release was foreshadowed in February, when authorities blamed the bloom on a "convergence" of events — including comments on the nutrient load from River Murray flooding as one of the main factors.

A full report was released today following what the SA government described as an independent peer-review process.

Report released late

But the date on the report dated back to May 15 this year, which has been questioned by some, including Greens senator Sarah Hanson-Young, who slammed the state government for not being up-front on the matter from the beginning.

"We know from the beginning they [SA government] were too slow to act and asleep at the wheel," she said.

When asked why the report was made public late, South Australia's Primary Industries Minister Clare Scriven said it needed to go through the processes, including being peer-reviewed.

"It needed to go to the Algal Bloom Taskforce, and be analysed by my office and the taskforce," Ms Scriven said.

"It was reviewed by independent reviewers from Tasmania and the United States."

But ecologist Faith Coleman, who resigned from SA HAB (Harmful Algal Bloom) Scientific Advisory Committee and SA Algae Bloom Reference Group earlier this year, said the report did not need to be peer reviewed and should not have taken that long.

"It shouldn't have needed to gone off and spend all the time from April to now being peer-reviewed, that is a lot of months," she said.

But she welcomed the transparency from the government saying the findings will be useful going forward.

The findings

The report found that there were three major contributing factors that triggered the ideal conditions for the bloom to develop, including floodwater, a coastal upwelling and a marine heatwave.

It was found that the bloom developed and intensified during an unprecedented marine heatwave.

The report stated that while temperature alone may not explain bloom initiation, the associated calm conditions, reduced wind mixing and enhanced water-column stratification were considered a key enabling factor, favouring motile dinoflagellates such as Karenia.

It said that multi-decadal analyses show that the bloom developed following a period of prolonged environmental pre-conditioning.

SARDI's executive director Professor Mike Steer said a comprehensive amount of research had gone into finding these out.

"This is really important information to understand because if we're going to develop a forecasting index for harmful algal blooms for SA or Australia in the future then we really need to understand these fundamental drivers."

He admitted there were still gaps in the data they have collected and analysed.

But Professor Steer said he was surprised how quickly the team was able to pull together the report.

"I thought it was going to take us a lot longer to get where we are at, but the foundation that we have set is really promising," he said.

Ms Scriven said while nothing could be done to stop the algal bloom from occurring, the research helps to be more prepared.

But Ms Coleman has asked the state government to release more data.

"It's not a rigorous review of the science that we would've liked to see at this point," she said.

"I'd like them to release the data about all of the other hazardous species that have occurred, not just Karenia."

Ms Coleman said she also hopes the government will change conversations around the Murray River — which was persistently blamed as one of the main contributing factors.

"That has been a major issue for us all the way along is the comment that it is the River Murray, because that impacts how we manage the biggest most regulated river in the nation," she said.

There's gap in the data

Professor Steer said there was still a lot that is not known and that it was going to take time to look at some of the knowledge gaps.

"One of the challenges in science is that in answering one particular question you generate ten more," he said.

Professor Steer said the report is a strong foundation for the new office to continue their research in collaboration with national and international jurisdictions.

This includes looking at topics such as, "The different biochemicals are produced by the harmful algal bloom species, the role the environment plays in persisting algal blooms, and understanding the impact on key recreational commercial fisheries and marine ecosystems," he said.

Going forward, Professor Steer said the algal bloom crisis and the report will set down precedent on how to deal with similar crisis in the future.

"Our focus now is on improving our science and understanding it so we're better prepared in the future."