North Australian FISH FINDER forums

Sea life dying as weird foam washes up on shore ... https://www.news.com.au/technology/envi ... 6a2e0aac52

Interestingly, this follows an extended hot water anomaly in the area, pic attached. The hot water anomaly has been around Tassie too, where they had the largest recorded die-off of farmed Atlantic salmon near the Huon (southern region). NZ also affected.

A few weeks earlier, hot water at the Pilbara may have killed fish off Gnoorea ... https://cosmosmagazine.com/nature/marin ... ling-fish/

Not sure if this is normal or result of climate change. With climate change, there's zero chance of any global remedy while Trump's running the USA, as he is busy cutting climate change-related research and clean energy programs while promoting "drill baby drill".

Image adapted from www.climatereanalyzer.org

Anyone here been following this? The bloom is persisting into winter ... Sharks, rays, squid cuttlefish, various fish, seahorses, crabs, pipis dead, it is even hitting the Coorong.

I lived and fished Adelaide during my teens, don't recall any fish kills then.

The bloom has been caused primarily by karenia mikimotoi which, according to Wikipedia, thrives where there is extra salinity (EDIT: This appears to be debatable).

This is interesting because the Adelaide and Kangaroo Island desalination plants were going full bore this summer because of drought.

The govt is saying it was not the desal plants pumping brine that caused this bloom. Maybe they are wrong and desal brine hit the warm water anomaly shown above and that caused the bloom.

Additionally, changes in the ocean, with meltwater and upwellings coming in from Antarctica, may have contributed fertility. The Southern Ocean is known to be changing from melting polar ice water flowing in.

However the Southern Ocean is becoming less saline [EDIT: latest study finds that it is actually becoming more saline, in a surprise twist, due to the ocean current unexpectedly changing].

Just speculating, yada yada.

This is a huge deal for SA, this massive bloom killed a lot of sea life. Will it repeat?

Suggest anyone interested in the SA bloom check this site ... https://www.inaturalist.org/projects/sa ... vents-2025

The map segment attached is adapted from that site, showing the reports of dead organisms. Funny how it's mostly around Adelaide waters. But perhaps that is where all the people are, and therefore more sightings.

Just read an article on the fast progress of ocean acidification from CO2, so tapped a question into chatGPT: Are predators of toxic Karenia more vulnerable to acidification than Karenia?

The answer is yes, so another factor at play here.


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What microorganisms eat Karenia?

ChatGPT said:

Karenia (especially Karenia brevis, the species behind harmful red tides) is a genus of toxic dinoflagellates. Despite its toxicity, certain microorganisms and small marine animals can feed on it.

These include:

1. Protozoan grazers

Ciliates (e.g., Favella spp., Strombidinopsis): These are small, often filter-feeding protozoa that can ingest Karenia, although toxicity may limit how much they can consume.

Dinoflagellates (e.g., Polykrikos, Gyrodinium): Some heterotrophic or mixotrophic dinoflagellates feed on Karenia, using feeding mechanisms like pseudopodia or engulfment.

2. Zooplankton

Copepods (e.g., Acartia, Temora): Some copepods can feed on Karenia, although they may avoid it if toxicity is high or if alternative food is available.

Cladocerans and rotifers: These are small planktonic animals that can graze on a variety of microalgae, including Karenia, though often inefficiently.

3. Bacteria and viruses

Bacteria don’t "eat" Karenia in the traditional sense but can decompose dead cells or form symbiotic or parasitic relationships.

Algicidal viruses or bacteria (e.g., Shewanella, Pseudoalteromonas): These can infect or kill Karenia, helping control blooms indirectly.

Summary

While Karenia is toxic to many organisms, some protozoa, dinoflagellates, copepods, and specific bacteria/viruses can consume or break it down, particularly when bloom conditions change or the cells begin to die.


Are Karenia predators more likely to be affected by acidification than Karenia?

ChatGPT said:

Yes, Karenia predators are generally more vulnerable to ocean acidification than Karenia itself, though the full picture is complex and context-dependent.

Here's why:

1. Karenia's physiology makes it more resilient

Karenia is a dinoflagellate with a cell wall made of cellulose, not calcium carbonate.

It performs mixotrophy (photosynthesis + ingestion), which may help it adapt under changing pH and nutrient conditions.

Some studies show that elevated CO₂ can even boost its growth, potentially worsening blooms under acidified conditions.

2. Predators like ciliates, copepods, and micrograzers are more sensitive

Many of Karenia’s protozoan and zooplankton predators experience:

Reduced grazing efficiency

Lower reproduction rates

Altered behavior

Weakened immune systems

For example, copepods, key grazers of Karenia, may:

Feed less

Avoid toxic cells more

Reproduce less under low pH

Ciliates like Favella show impaired feeding or even mortality when exposed to acidified conditions, depending on the strain.

3. The imbalance tips in Karenia's favor

If predators are suppressed more than Karenia is harmed (or if Karenia is even slightly helped), then:

Top-down control breaks down

Blooms become more intense or prolonged

This is already observed in some experiments and field studies.

Summary:

Yes, many of Karenia’s predators are more vulnerable to acidification than Karenia itself.

This makes Karenia more ecologically dangerous under future ocean conditions — potentially increasing red tide risks.

So, in summary, you've got hot water, still conditions, sunlight from the drought conditions, with possible raised salinity and/or stratification coming from the shallow gulf and the desalination brine, plus increased ocean acidity hobbling Karenia predators.

There was a recent meeting of experts who are studying this bloom, will be interesting to read their findings.

Coorong hit ... https://www.theguardian.com/environment ... ogist-says

Not a good situation Matt, im going to have a go at some whiting in 2 weeks time off York's so i will let you know how i go. Normally plenty of fish around late june, July

Hope you get a few

Been giving this SA bloom some thought because I am a former Adelaide fisho.

Has to be something more than just warm water etc as there is warm water elsewhere. Why SA? Where could a unique nutrient load come from?

Possibly fish farms. Spencer Gulf has many tuna and kingfish farms. Tuna farms are rich sources of dissolved nutrients, especially nitrogen.

Annually, SBT operations in Spencer Gulf release about 1946 tonnes of nitrogen into the water - significantly more than local wastewater plants combined, which release around 54 tonnes per year (says Chatgpt). Add on the kingfish farm output.

So that's a factor that might have contributed. Or not.

Murray River flooded in 2022/23 but you'd think that fertility would be long gone, and it has flooded many times before.

Problems also in Tassie linked to fish farm pollution ... https://www.abc.net.au/news/2025-06-02/ ... /105354680

Recent government media release says there was an unprecedented deepwater upwelling that may have contributed nutrients to the bloom. They also mention the 2022/23 flood.

Might have been a bit of all the above-mentioned, who knows. Lots of dead stuff on Adelaide beaches currently.

Experts now saying the bloom may be around for a year or more.

Has been a statement that it's not toxic to humans, even though it was first reported by sick surfers at Waitpinga, and dead kangaroos were found near an affected beach (roo deaths since blamed on them eating a type of grass), also dolphins and seals (mammals) have died.

Studies seem to have found that Karenia m. is toxic, killing nerve cells. A quote ...

"Toxic dinoflagellate Karenia mikimotoi induces apoptosis in Neuro-2a cells through an oxidative stress-mediated mitochondrial pathway"

https://www.sciencedirect.com/journal/e ... tal-safety

http://www.researchgate.net/publication ... l\_pathway

http://www.researchgate.net/publication ... al_pathway

Edited excerpts:

"Effect of K. mikimotoi on cell viability ... cell viability assays indicated K. mikimotoi is cytotoxic to cultured red sea bream gill cells (Ohkubo et al., 2017) and several other mammalian cell lines (Chen et al., 2011), including the neuron-like N2A and SH-SY5Y cells. Based on those previous studies (Chen et al., 2011, Niu et al., 2021), we speculated that K. mikimotoi has neurotoxic effects, and might threaten the public health via the food chain. (Nerve cell) death or damage induced by neurotoxins is irreversible, which is tightly associated with neurodegeneration diseases (Mello et al., 2018, Botelho et al., 2022).

"This study demonstrated that K. mikimotoi RCS exposure is toxic to neural cells in a dose-dependent manner. The neurotoxic effects of K. mikimotoi are related to the overproduction of ROS, increases in MDA, and reductions in SOD activity and MMP. K. mikimotoi also altered the expressions of some key genes associated with cell apoptosis and the antioxidant system. These results suggested that K. mikimotoi RCS induces neurotoxicity via a mitochondrial-dependent apoptotic pathway. The findings presented herein will lead to further research on public health risks of HABs, including neurodevelopment disorders and neurodegenerative diseases."

Got a feeling this bloom may have bigger impacts than is currently being openly acknowledged.

Freshwater blue green algae blooms already have suspected connection to ALS, with clusters found around affected waterways.

Typing on my phone, apologies for any typos.

Lastly, I spent a day at Victor Harbour and walked beach at Port Elliot during the bloom, came home with a headache and runny nose. Maybe just a coincidence, but it was odd.

Also, Normanville jetty washed away in a storm (among others damaged in SA's winter of 2025), not the most important fishing jetty in the scheme of things, but geez ...

The 2022/23 Murray flood is being touted as the source of nutrients, but the SA current flows eastward, so why did western Vic waters not get the bloom?

From chatGPT ...

"During the 2022–2023 Murray River flood, the coastal current off southeastern Australia, particularly near the Murray Mouth and Coorong region, was flowing predominantly eastward along the South Australian coast, consistent with the usual direction of the South Australian Coastal Current (SACC) during summer.

Coastal current summary during the flood:

Main current: South Australian Coastal Current (SACC)

Direction: Generally eastward, from the Great Australian Bight towards the Murray Mouth, then continuing along the Coorong and toward western Victoria.

Seasonal influence: In summer, prevailing southerly winds strengthen the eastward surface current flow.

Upwelling: These southerly winds also drive upwelling near the coast, bringing nutrient-rich cold water to the surface, but this doesn't reverse the current."

My fishing chalet is at Port Moorowie, 20km due west of Edithburgh, on the bottom of Yorke Peninsula.

2nd Sat in April I was on a Sea Rescue training run out from Edithburgh (5-6+ Nm) and there were hundreds, if not 000's of small dead fish. This was before the algae was proclaimed. 6 weeks ago, walking the Moorowie beaches there were dead fish (mainly small sharks, puffer fish and rays) every few meters. .. and not just at the waters edge - from the waters edge to the high tide mark and far a long the beach.

Last weekend, same beaches, only 1 squid and 2 puffer. Hopefully the 'plague' has been washed from the area by the big storms we endured a few weeks ago. THe storms did incredible damage to the cliffs and dunes so likely cleared the algae and disposed of the corpses..

Appreciate the feedback dmck. Hope it turns around for you soon, some great country down there.