A toxic algal bloom is continuing to kill fish along a substantial part of the South Australian coast. The bloom has grown to affect around 150km of coastline now and is as deep as 20metres.
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00:00So it first popped up halfway through March and so over the last sort of eight weeks it's
00:08spread further west so it popped up around the Florio Peninsula and now it's spread out to
00:14Kangaroo Island and areas around there. And what's causing it? So it's caused by a particular species
00:21of marine microalgae of the genus Carinia. So initially it was Carinia micimotoi was the
00:28species that we were seeing. Now we seem to be seeing other species of Carinia as well as micimotoi
00:34and so it seems to be a mixed bloom but basically Carinia micimotoi. And what are the environmental
00:41factors that make it possible for a bloom like this to grow? So that is a question we can't answer
00:48and we probably won't be able to answer that for some time. So blooms like this of Carinia micimotoi
00:54pop up all around the world. There have been a really big problem in China for example
00:59and there's a range of environmental conditions that these species experience so we'll really
01:07have to look into all of that data once we've got all the samples and the bloom's over.
01:12How much damage is it doing to marine animals, local industry and the environment?
01:20So the oyster industry in the area is closed for harvesting. In terms of other the marine
01:28environment it's caused deaths of marine many different species of fishes, shellfish, marine
01:35invertebrates and marine birds. So yeah, it's caused substantial damage and these blooms
01:42have caused substantial damage overseas as well, particular blooms of Carinia.
01:48And is this bloom likely to be there for some time yet?
01:53We don't know, again. So the only way to study these things is really to take those regular water
01:59samples and unfortunately with this particular bloom that that hasn't been possible. So and even
02:06even there it's not always easy to predict how long a bloom is going to last. My best guess would be if
02:13some kind of new weather conditions come through then it could break up the bloom and make it move it
02:18further away. So we'll just wait and see. Yeah, I've noticed in some coverage of this some people have
02:25mentioned water temperature as having something to do with the bloom and the fact that it's lasted so
02:31long could be to do with strong weather systems not coming through. Have you got any observations on that?
02:39I'm not sure. I think Carinia Mikimoto specifically has a temperature optimum of around about 20 or so
02:46degrees. So when it's warmer than that it actually doesn't necessarily like it. So I think we need to
02:51really wait and see once we've got all the data and we'll be able to work it out. Yeah, right.
02:56And so and this is like it's we're used to with news stories seeing these toxic blooms in rivers
03:04but are they kind of are they quite rare in coastal areas? No, they're actually really common
03:12but we don't necessarily see them because they don't often cause fish kill so often they might just cause
03:18some sort of toxicity. But the aquaculture industry for example are very familiar with harmful algal
03:24blooms and they have a regular system of monitoring in place to make sure that they close their harvesting
03:31if there's something like this. But it is completely different species of harmful microalgae that you get
03:37in marine waters compared to the river systems. So in the river systems you get the cyanobacteria that has
03:43that very blue greeny tinge to it and in marine systems you don't see that. They sometimes look brown
03:49or they can look a bit reddy but they look very different. And how does this kill, well how does this
03:55lead to animals dying? So Carina mikimotoi seems to produce something called reactive oxygen species. So
04:03it's a type of effect when the cells, when the skin cells of the fish come in contact with the
04:10Carina mikimotoi cells and this can cause damage to the fish's gills. So then the fish are not able
04:17to breathe properly. So usually there's some effect in relation to that. And this is spread over such a
04:24big area, yeah the officials are now saying 150 kilometres, but this isn't the biggest toxic bloom,
04:30a coastal bloom Australia has seen? No, no. So we've had blooms of other species, so for example
04:38Alexandrium pacificum and Alexandrium catenella in New South Wales. One in New South Wales that's covered
04:46most of the state, so almost a thousand kilometres long, and a bloom of Alexandrium catenella
04:52that covered most of the east coast of Tasmania in 2013-2014. And that bloom in particular caused
04:59about 23 million in damage to the aquaculture and fisheries industry in Tasmania. So we have
05:06had many harmful algal blooms in Australia. I think the difference with this one is because it's a fish
05:11killing bloom, it's very visible and the effects are kind of more obvious in that it's affecting
05:20more species of fish and it's causing the direct deaths of a lot of marine life.