17/07/2025
Great post by Gazander Oysters! If you’re wanting to learn about the algal bloom and its effects on the oyster industry. Just for reference for those asking; Mooka oysters isn’t located in Coffin Bay, we are approx 400kms west in Smoky Bay.
🦠Karenia Blooms, Brevetoxins & What’s Really Happening in Our SA Waters
*This is our personal interpretation of current situation from information I have read, sought and gathered. Sharing to shed an easily read and understood explanation. Much love and support to those directly affected. Our hearts hurt for you. *
Hi all,
There’s been a lot of media coverage around the current algal bloom, and we have done a few interviews this week to help explain what’s really happening. A comment we keep hearing is: “I hope it doesn’t reach Coffin Bay.” But the truth is, it’s not about the bloom “reaching” new areas — it’s not something that moves like a slick. It’s already here.
Karenia spp., including Karenia mikimotoi, are naturally present in South Australian waters. They’ve likely been here since the 1960s, introduced through ballast water from ships, and are now found in most major harbours around the state. These algae are always in the background — they just need the right conditions to bloom.
What we’re seeing now is the result of a perfect storm of environmental factors:
• A prolonged marine heatwave
• Delayed seasonal temperature drops
• Late winter rains
• Exceptionally calm wind conditions
• And likely nutrient-rich runoff from major inland flooding events
All of that, combined with a huge nutrient load left behind from last year’s upwelling (you’ll remember the water turning green), created ideal conditions for Karenia to take off. And now, every time the weather stirs things up, that nutrient-rich sediment is re-fed into the system, helping the bloom persist longer than expected.
We’ve seen this before — Coffin Bay in 2014 experienced a bloom that lasted 3–4 months, impacting oyster nutrition and decimating many species I personally remember particularly scallop numbers. That bloom eventually broke down with strong seasonal winds and storms — but this time around, those systems just haven’t come with enough strength or consistency.
Why Some Harvesting Areas Are Closed
In areas like Stansbury and Kangaroo island harvesting has been temporarily suspended due to brevetoxins produced by Karenia species. These toxins, while not harmful to shellfish themselves, can accumulate in filter feeders and trigger closures under our strict food safety standards.
These closures are precautionary, based on rigorous, ongoing testing. They’re about protecting public confidence and ensuring long-term sustainability of the seafood industry.
Impacts on Marine Life
Karenia blooms also affect marine species by:
1. Depleting oxygen, especially when blooms collapse
2. Releasing toxins that can damage fish gills and affect oyster and scallop health over time
Even in open areas, persistent bloom conditions can put pressure on marine ecosystems.
No Downplaying – Just Explaining
In no way are we minimising the challenges faced in other regions. This has been a serious and devastating event, and its persistence has taken even scientists by surprise.
This post is about helping people understand what’s happening — how these blooms behave, what environmental factors may be fuelling them, and why certain areas are affected differently.
Eyre Peninsula Is Open for Business
93% of South Australia’s aquaculture-raised seafood comes from the Eyre Peninsula, which remains fully open.
We’re still producing incredible oysters and seafood, and they’re available now — fresh, local, and safe to enjoy. Supporting these producers directly helps the small businesses and regional communities that depend on them.
And When Others Are Ready…
When impacted communities are able to fish and farm again, we must be ready to back them — commercially, financially, and emotionally.
This industry isn’t just a job — it’s a way of life. It demands everything: time, energy, resilience, and heart. And the people in it do it because they love it. So when they’re ready to return, we need to ensure they’re supported to keep doing what they do best.
We Are All Ocean Stewards
Those of us who work on the water consider ourselves stewards of the ocean. Yes — we rely on it for our livelihoods, but we also deeply respect it. We want to protect it not just for ourselves, but for future generations — to ensure there’s food security from both land and sea, and healthy oceans that continue to support life.
But this responsibility isn’t just ours — we all share it. Every one of us has a role to play in how we treat the environment. And right now, we know many in the public are watching closely, doing what they can to learn, help, and support.
So let’s keep going. Let’s push through the hard times together, support one another, and keep working toward a stronger, more sustainable future — for our waters, our communities, and the generations to come.
