Authorities are investigating whether the deaths are connected to an algal bloom last month, which was identified as the cause of a mass fish kill from Waitpinga to Basham Beach in the Fleurieu Peninsula, impacting a wide variety of marine and coastal wildlife.

A dead penguin was spotted lying on Goolwa Beach. Source: SBS News

Underwater photographer Paul Macdonald, who runs dive tours nearby at the Edithburgh Jetty, across the bay from Adelaide, said the extent of the deaths has been heartbreaking to witness.

He said over the weekend he cancelled dive tours due to the “murky brown” water, but he went for a dive on Sunday to check the state of the marine life there and was shocked at what he saw.

“Fish like goldfish, snook, Tommy Ruff … there were dead starfish, dead crabs, dead sea cucumbers.” 

Dozens of dead blue-ringed octopuses have been photographed at the Edithburgh Jetty dive site. Credit: Paul Macdonald

Macdonald said the Edithburgh Jetty is a globally renowned dive site and the marine life there is usually “prolific”.

“Nowhere in any of my diving have I seen anything quite so bad, there was almost no life.”

Divers have reported a wide variety of fish species lying dead underwater. Credit: Paul Macdonald

Warming waters

Algae blooms of this type have caused mass fish and shellfish death events in Japan, New Zealand and South Australia’s Coffin Bay, the EPA says.

“The department … has commenced investigations into the event with cockle and water samples collected for testing,” a PIRSA spokesperson said in a statement on Monday.

RecFish SA said it has mobilised members and citizen scientists to investigate the causes of the recent fish kills. Credit: Recfish SA

Macdonald said this is the first time he’s seen an algal bloom of this scale.

“My [diving] log book goes back 35 years … recording the temperature of the dives and looking at the same similar dates through time, the water … in the middle of summer at Edithburgh is a couple of degrees warmer than it was, say, 20-25 years ago.”

Calls for urgent investigations

“We’re talking very important fisheries and recreational fishing is a very valuable contributor to the South Australian economy.”

Cockles are an important part of South Australia’s fishing economy. Source: SBS News

Brown said RecFish SA is undertaking its own testing and has hired divers to investigate the health of reefs further away from the shore.