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Dr. Watson: It is widely thought that climate change will generally increase the risk of cyanobacteria blooms in these and other lakes, because many of these species are favoured by warmer temperature, more storms and intense runoff from fields and urban centres, less ice cover (and extended growing season), changes in wind, precipitation and other factors that affect water levels, mixing and circulation in lakes.
WaterToday: Can you elaborate a bit on the different species of cyanobacteria?
There are several cyanobacteria we now see blooming in the Great Lakes (there’s never just one) – but the species that everyone is really worried about is called Microcystis which dominate many of the present-day blooms in Lake Erie. Some of these can produce microcystin toxins. Microcystis was one of the first cyanobacteria found to produce this group of toxins when we started identifying what it was in water that was killing off cattle.
There are also lots of different types of microcystins produced by cyanobacteria; some a little bit more toxic than others. One problem with microcystins is that they are in general very, very resilient to chemical treatment, to UV radiation, etcetera. So once released, they can persist in the water long after the cells that produced them have disappeared. And that is one of the biggest problems that faces beach managers and water treatment plant operators.
People are focused on the bloom material – which when living and healthy, keeps most of the toxins inside the cell. But should you break those cells open, for example, as a result of some kind of environmental stress, disease, predation or treatment with chlorine or other chemical treatment, they will release these toxins into the water and the dissolved toxins are very much more difficult to remove,and also tasteless and odourless – in other words, they cannot be detected unless analysed using special kits or lab procedures .
And a lot of times people may think that, “the bloom’s gone, no problem.” Or they’ll access an area where there’s been a bloom and it’s disappeared, and they’re not aware of this.
WaterToday: Right. I’ve seen that and at first hand.
Dr. Watson: Yes. There are some agencies, for example Hamilton Health, that use toxin test kits in their beach monitoring program and monitor for the dissolved toxins after the bloom is gone. And they only open the beach when the toxin levels are below levels that present a risk to human health.