An unprecedented toxic algal bloom in South Australia’s Coorong has caused death on a massive scale to many local marine species. Local researcher Glen Hill went one step further, gathering samples from the North Lagoon. It was in those samples that he found the harmful algae species, Karenia mikimotoi. This bloom has already claimed the lives of thousands of polychaete worms, crabs, and small fish, raising serious concerns about the ecological health of the region.
The bloom covers about half of the North Lagoon, stretching all the way north towards Long Point. Stormy weather combined with high tides provided the perfect conditions for this disaster to transpire. Because of this, the Karenia mikimotoi-dominated algae cocktail was pushed into the lagoon through the opening of the River Murray mouth. Those on the scene reported a curious deep reddish-pink hue coloring the water. It was teeming with dead and dying fish and other aquatic creatures.
Effects on Local Ecosystem
Fishing south lagoon last week As Tracy and Glen Hill headed into the southernmost section of our North Lagoon last week. On their trip they experienced an alarming deterioration in water quality. The couple discovered dead and dying polychaete worms, signaling deep ecological degradation at alarming levels. Although he was shocked by the news, Glen Hill knew his community would persevere.
“I spent a fair bit of time crying over what I was seeing.” – Glen Hill
The addition of Karenia mikimotoi is a double whammy as it puts the local marine life at risk while causing negative impacts to the planet’s larger ecosystem. Resident fisherman Gary Hera-Singh said the water was starting to look “almost black” on one side of the lagoon. He showed us where hundreds of colorful bristle worms were just under the surface. As he continued to elaborate on just how essential these tiny organisms known as zooplankton are to our aquatic food web.
“The minute animals that live in the water column and in the sediments, they’re a really important ecological link to everything else above it, whether it’s birds or whether it’s fish,” – Gary Hera-Singh
As this massive algal bloom continues to expand, its effects on marine biodiversity are sure to be catastrophic. We still do not know the true scope of aquatic mortality. Even more material from the lagoon’s bottom would end up on shore during windy days.
Scientific Observations
Faith Coleman is a committed scientist who has fought with Glen Hill for decades to protect the health of Coorong, their restoration zones. A few weeks ago, she tested a particular batch of algae and shared some very troubling results. She explained that with the algae, you could already see it starting to get established in that environment of the lagoon.
“I was in tears. I didn’t realize how bad it was until I couldn’t see my slides down the microscope and my teenager came in to ask if I was OK,” – Faith Coleman
The algal bloom can increase extremely quickly, as it multiplies through self-division. This remarkable reproductive capability, coupled with Georgia’s warm, wide-open lagoon waters, makes the lionfish an acute threat to the Lagoon’s local ecosystem. Coleman wanted to stress the extreme salinity conditions in the Coorong. He suggested that the abundant food supplies found in the area may enhance sexual reproduction of these detrimental algae.
Community Concerns
For months, local residents and commercial fishery operators have voiced increasing concern about the health impact and economic threat posed by this algal bloom. The future of the Coorong’s health is enormously important to all the species that live there. It directly uplifts the agencies’ mission by sustaining the livelihoods of people who rely on its resources.
As for the bloom itself, Gary Hera-Singh noted how unprecedented this bloom is, pointing to its unusual characteristics and strong smell.
“It’s not a bloom I’ve ever seen before … it gives off this very pungent odour,” – Gary Hera-Singh
He reported seeing algae so thick that it was “as thick as pea soup.” That means that this occurrence is very different from any other events on record in the region.
