Changes to natural water flows have put significant pressure on a protected wetland as scientists warn more monitoring is needed to predict the next toxic algal bloom.
A study drawing on 16 years of data into water quality of South Australia's Coorong found more than 80 species of phytoplankton capable of producing toxins that can cause harmful algal blooms in the waters.
While samples showed the levels of species were low overall, researchers warned poor water management in the Murray Darling Basin could risk tipping the balance of the wetlands and surrounding lower lakes.
"It's important to document what's actually there because maybe there are some conditions that we haven't seen yet that mean that maybe they could bloom," Flinders University academic Daniel Chilton said.
"In a lot of natural systems there are still a lot of potentially harmful species. I guess it's just that you need the right conditions for certain ones to bloom."
Spanning 140km long, the Coorong is the final stop of the Murray River waters and is considered a key indicator for the health of the Murray Darling Basin.
Barrages built in the 1930s have replaced regular pulses of fresh water into the lagoon system to control nearby lake levels and prevent high salinity moving upstream during low river flows.
Marine biologist Sophie Leterme, who led the study, said major changes in salinity and water level from both sides of the spectrum were the major drivers in producing abundant communities of phytoplankton.
"When there are discussions about putting pipes in the middle of the Coorong to suddenly bring a lot of water in, or if suddenly we remove the barrage again...what sort of condition is it going to create for those species to suddenly start blooming and be more abundant in the environment?" she said.
"And I think that's a risk sometimes that people don't fully consider."
The study, led by Flinders University, is among the most comprehensive analyses of the Coorong's water quality, yet Dr Leterme said scientists weren't funded enough to properly monitor the looming communities of algae.
Up to 10 years of research was missing from the study due to funding gaps, while the team could only take samples every four months.
"If you really wanted to know what the risks are and if some blooms of harmful algae are taking place, you would have to monitor the quota on a monthly basis for many years," she said.
"What we've seen with the harmful algal bloom here in the gulf is really that if you don't monitor properly, you might actually miss a warning sign before it's too late."