For any of you who may be interested in the details of the toxic algal bloom currently affecting our waters, and for many of us who have been in them over the last couple of months, this week there was a forum discussing many aspects of this event. I was in the mix, talking about the toxins themselves and their possible effects on different creatures, including humans. Here is a link to the Youtube recording of the forum:

Bit of a long video. Is there a clue what's causing it? Is it possibly the result of excessive fertiliser use and discharge or rising water temps or unsure still?

Thanks for sharing Ian. I didn't recognise you without your zinc and lid

Is this the same effect we see at the northern beaches at about March/April every year ?, where everything dies off ? (sea grass, coral, razorfish etc). The water normally turns a reddish colour in the inside that looks like algae.

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ptsf1111 said..
Bit of a long video. Is there a clue what's causing it? Is it possibly the result of excessive fertiliser use and discharge or rising water temps or unsure still?

The main trigger for the bloom was an uprising of nutrient-rich deep water off the SE coast, which then drifted up towards KI and Yorkes, where it has been maintained by a variety of factors: light winds, warm surface temperatures and possibly some kind of positive feedback effect of the high numbers of algae. Fertilisers are probably not the primary driver in this case. Fertilisers and other nutrients derived fron land run-off can trigger blooms, but they tend to be different types of algae compared with what we have here.One thing that can be 100% ruled out is anything to do with the desalination plants.The video is long because there is a lot of info to sort through and potential explanations are not straightforward. I reckon we could have continued discussing the finer points for another 2 hours! My section of how the potential toxins work only skimmed the surface of what's known and what's likely to be happening.

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jn1 said..
Thanks for sharing Ian. I didn't recognise you without your zinc and lid

Is this the same effect we see at the northern beaches at about March/April every year ?, where everything dies off ? (sea grass, coral, razorfish etc). The water normally turns a reddish colour in the inside that looks like algae.

Damn, the disguise is broken!!!This bloom is quite different from that seen up the Gulf late summer. I can't quite remember the details of that, but I'm pretty sure it's a combined result of changes in water temperature, nutrient levels, and perhaps salinity. There are many type foods algae that can bloom to varying degrees. The sea grass can be killed off by a combination of excess algae floating in the water, which reduces both light and oxygen availability to the grass, as well as excessive growth of algae on the sea grass itself, which effectively chokes it. The same thing probably affects the shellfish to some degree as well. Once the seagrass dies off, then the complex communities of fish and other creatures that depend on it are under threat.There may be some kind of cyclic die-off of the seagrass, I think, the effects of which we see as the large pile-ups on the city beaches after strong NW winds early in winter. Having said all that, there is considerable evidence that the sea grass beds in both Gulf St Vincent and Spencer Gulf are in severe decline over the last 20 years or so. This is largely attributed to changes in the marine environment probably caused by uncontrolled run-off from land containing high levels of fertilisers and a vast mix of toxic by-products of human activty, including sewerage and industrial contaminants.

Ok, thanks for info. I imagine the annual metro die off is even more complicated due to the River Torrens, which is an unnatural river outlet.

Nb/ Surprised to learn from 2nd presenter that this bloom was not caused by heat wave (or words to that effect). This was the conclusion everybody has been jumping to, including me. As you said, this is a complex process that is not straightforward to understand.