The Bloom We Can’t Ignore: How Misunderstanding and Inaction Are Harming Our Seas

The Karinia mikimotoi dinoflagellate bloom that began in early summer this year is taking its toll on sea life, with little understanding of what can be done to mitigate its effects. All industry and the businesses reliant upon it are in various stages of trouble, in some cases this means entire towns. The Government has been slow to act at every step, with their main strategy appearing to be hoping it will simply go away. Yet the chances of this happening in the short term were always unlikely and are becoming less and less likely as time goes on, and those of us at the coalface learn more about its causes.

The drivers for this have been building for two years, and alarmingly, there is still no clear understanding by Government and the Department for Environment and Water as to what they are. In that void, people are inventing their own explanations. This has created a huge problem for everyone at the coalface, requiring time that simply doesn’t exist to put forward relevant and reasoned information. The problem is that the claims being circulated are unsubstantiated, some quite alarming, and are not linked causally or logically, but only by similar timing and/or location.

Some of these claims include Chinese submarines, the desalination plant, ballast water, fertiliser runoff, and nutrient loads from the flood. Others blame cruise ships dumping effluent or vessels removing algal build-up from their hulls. The problem with such outlandish claims is that people spend time developing them and become very attached to them, reluctant to let them go. Instead, they often double down, adding extra information that makes the claims even less credible.

Once these theories gain traction, they are next to impossible to debunk, even with a logical, evidence-based process that rules them out. Unfortunately, this distracts from the very real issue of climate change and what has actually caused this devastating bloom.

Then there are those who are trying to use the situation for their own ends. For example, the ever-ready team of irrigation lobbyists who claim that it is South Australia’s fault for releasing water through the Murray Mouth from the Lower Lakes before it was tested for nutrients. While their argument is that the water should not have been released, what they are really after is more water for irrigation.

Then there is RecFish SA, who previously claimed that the fish were unsafe to eat, yet have just received a grant of half a million dollars and have now changed their position to the extent that their Executive Officer says he would confidently feed fish to his two-year-old son. Perhaps he was told to pull his head in?

For the commercial sector, which is already struggling to catch and sell fish while justifying its existence, this is just another blow. Conflating the issues will always have unintended consequences, and all too often it is the seafood industry that takes the hit.

On a more positive note, this vacuum has encouraged the rise of an integrated citizen science effort, which has attracted scientists of calibre who have joined at their own cost and loss of wages. This movement continues to gain pace and support from the general public, and it will be interesting to see how it evolves given the amount of information and learning being generated.

Despite this, the Department appears to want all information handed to them so they can “take it from here”, yet they continue to release statements containing incorrect information. To this day, the Government and its spokespeople still put forward causes that make no sense.

The Government, various ministers, and their departments have been so slow off the mark, despite ample warning this was coming. Climate change science has long predicted these types of events would become increasingly common. There has been evidence of similar events overseas for years, yet we do not have a specialist facility in Australia to even identify the species in this bloom.

So, what happened?

In 2022–23, the Murray floods occurred. However, it is now 2025. Nature doesn’t wait two or three years to use available nutrients, with the exception of nutrient pushed off the continental shelf into the deep ocean, nature’s way of “banking” resources for future use. While some nutrient was used during the flood, the majority went off the continental shelf two years ago. It is then pushed back gradually, feeding various simple algae and diatoms, the food source for the Goolwa cockle (or pipi) beds, as well as seagrass meadows and complex algae such as kelp.

Last year, there was an extended upwelling period, which would have extended the growth of the seagrass meadows, a perfectly normal and desirable outcome. However, the WA Lewin Current was very strong last summer, probably fed by the Indian Ocean Dipole, and reached as far as South Australia, bringing warm water and halting the upwellings that usually cool inshore waters during summer. This caused a marine heatwave, with temperatures between 2 and 5 degrees above normal.

Remember the goal of keeping global warming below 1.5 degrees to avoid the worst impacts?

This heatwave caused the shedding of seagrass and algae which, as it decomposed, released dissolved organic carbon, the perfect food source for this bloom. Dinoflagellates are “lazy” in the sense that they prefer this readily available nutrient source over the energy-intensive process of photosynthesis. This was likely the main factor that gave them the competitive edge needed to reach bloom levels.

Why then does the South Australian Government keep saying it was caused by the Murray flood? Two possibilities seem likely:

1. The Department does not understand what actually happened and is therefore giving poor advice to the Minister and Premier.

2. People may be using this as a means to pursue political outcomes, the Murray–Darling Basin Plan comes to mind.

One thing is very clear for the commercial fishing industry, they are taking all the hits, copping much of the criticism, yet still striving to achieve better outcomes for the environment, which now so urgently needs our help.