Marine algal bloom spreads to SA's Coorong as fishers find dead creatures in North Lagoon

Australia Broadcast Center

4 days ago

Algae from a bloom that has killed marine life throughout South Australian seas over the past few months has been detected in the fragile saline environment of the Coorong.
The Karenia mikimotoi-dominated algae mix is believed to have entered the North Lagoon via the mouth of the River Murray during last week's stormy weather and high tides.
It has killed thousands of polychaete worms, as well as crabs and small fish, with fishers concerned for the environment and commercial fishery that depends on its health.
The Coorong is a Ramsar-listed wetland known for its global importance as a breeding site for pelicans and migratory birds.
Estuarine ecologist Faith Coleman, who has spent much of the past few months helping coastal communities understand the algal bloom, said she was "devastated" when she realised the algae was in her beloved Coorong.
The sample Ms Coleman examined was brought to her by commercial fishers Tracy and Glen Hill.
While fishing in the southernmost part of the North Lagoon late last week, Mr Hill noticed the water had a strange reddish-pink colour, and in places was full of dead or dying creatures.
"There were huge numbers of polychaete worms, all different sizes, types," Mr Hill said.
While Mr Hill was familiar with fish kill events happening in the more saline South Lagoon after stormy weather, he thought of the North Lagoon as a "refuge zone".
"I spent a fair bit of time crying over what I was seeing."
Fellow commercial fisher Gary Hera-Singh also noticed the change in the water.
"It's not a bloom I've ever seen before … it gives off this very pungent odour," Mr Hera-Singh said.
Mr Hera-Singh described the water as "nearly black" on the side of the lagoon next to the dunes that separate it from the ocean.
Like Mr Hill, Mr Hera-Singh was shaken by the sheer number of dead worms.
He believed the full extent of the aquatic deaths would not be known until more material at the bottom of the lagoon washed ashore on windy days.
He said other fishers had told him the bloom now extended as far north as Long Point and was affecting around half of the North Lagoon.
He said commercial catches in the affected areas were "non-existent", and he had grave concerns for the future of the fishery and thousands of birds that lived in or visited the Coorong.
Ms Coleman said the algae was already showing signs it could become established in the lagoon environment.
While samples of the algae collected from the sea were shown to be reproducing via cell division, she said the algae in the Coorong was reacting in a different way.
"In the Coorong, there is so much food, and the salinity is so good, that we're seeing sexual reproduction occur," Ms Coleman said.
Ms Coleman said that reproduction often led to more persistent blooms, and where the algae had penetrated lagoon areas overseas, blooms had even become annual events.
Mr Hera-Singh said much more extensive research was needed.
"This bloom has come in with a massive thump," he said.
"I'm still waiting to collect enough evidence to say whether we've got a future [as fishers] or not.
The South Australian Primary Industries and Regions Department (PIRSA) said it was investigating reports of a bony bream fish kill in the Woods Well Bay area and a polychaete fish kill at the Long Point area of the Coorong.
"Samples [including water samples] have been collected for both locations with results still pending," a spokesperson said.
"PIRSA would like to remind the public of the advice from SA Health for people to avoid collecting or eating any fish or marine organism found washed up and either dying or dead."