By Sue Tiffin
Cyanobacteria are one of the oldest organisms on the planet, evolving about three billion years ago, but there is still much for us to learn about cyanobacteria and their associated blue-green algae blooms, so last Tuesday night, more than 300 people signed up for a virtual Enviro Cafe hosted by Environment Haliburton to hear more about the ecology of what is commonly called blue-green algae.
Blue-Green Algae: The Good, the Bad, and the Ugly was presented by Dr. Elizabeth Favot through a popular Zoom meeting held in the evening of Feb. 9. Favot recently completed a PhD in biology using paleolimnology to examine long-term environmental conditions and potential drivers for cyanobacterial blooms in Ontario lakes. She’s a new resident to this area, and is working as assistant lake stewardship co-ordinator with the Federation of Ontario Cottagers’ Association, and the Ontario Ministry of the Environment, Conservation and Parks Dorset Environmental Science Centre helping to organize the Ontario Lake Partner Program, the largest citizen science water quality monitoring program of its kind in Canada.
First off, she explained, while blue-green algae is the more commonly used term, the more correct term is cyanobacteria, which is used in the scientific community. Blue-green algae are cyanobacteria, she said.
“The reason that the term blue-green algae is misleading is because cyanobacteria are actually fundamentally different from other true forms of algae like the diatoms or green algae, rather, cyanobacteria are photosynthetic bacteria.”
With that said, she noted that cyanobacteria are one of the oldest organisms on the planet.
“The blue-green algae played a critical role in the evolution of nature as we know it, because they were responsible for the great oxidation event of our atmosphere,” said Favot. “Because of this really long evolutionary history of three billion years, cyanobacteria are well-adapted to many different conditions and so you can find them in most illuminated environments on earth.”
Currently, there are more than 2,700 described species of cyanobacteria, though in time there will likely be more discovered.
“Of all the thousands of species of cyanobacteria, there’s only a handful or a couple dozen that form blooms in fresh water,” she said.
Blue-green algal blooms have been confirmed as recently as last November in Dysart et al, in Minden Hills and in Highlands East, according to the Ministry of the Environment, Conservation and Parks at that time.
“There’s actually no strict scientific definition but it generally describes a visible accumulation of algae, so it’s [when] one or a few species come to dominate the algae community in a waterbody,” said Favot. “But blooms can be measured in different ways. So, for instance, blooms can be measured based on total cell counts per litre of water, or based on the proportion of the algal community that’s made up of by a certain species or based on concentrations of photosynthetic pigments like chlorophyl.”
While they’re referred to as blue-green algal blooms, they are actually not necessarily blue-green in colour. In her slides, Favot showed a collection of photos – three that suited the blue-green descriptor were actually duckweed, green algae, and pollen, while three photos showing cyanobacteria ranged in colour from chocolate milk brown, to spinach soup green.
“Even to the trained eye, sometimes blue-green algae blooms can be tricky to distinguish from other types of algae or other growths on the water, until a sample is put under the microscope and then it’s very easy to tell,” said Favot. “Generally if you see kind of a consistent, opaque, pea soup green, it could be cyanobacteria, and you can call a biologist and they’ll figure it out for you.”
As Favot noted, blue-green algal blooms have been on the rise worldwide, and have been detected in more and more waterbodies over the last few decades.
“In Ontario specifically, the number of confirmed cyanobacterial blooms each year … has significantly increased over the last two decades, and the bloom occurrences are quite wide spread across the province,” she said. “And although maybe you’ve heard that nutrient pollution from run-off is the most common culprit of cyanobacterial blooms globally, which is true, about one in four of these confirmed blue-green algal blooms in Ontario are actually from lakes with average total phosphorous concentrations in the oligotrophic, or very low range. And still more bloom reports are coming from lakes where nutrient levels have been stable or even declining in recent decades. So the lakes that my research is focused on are ones that deviate from the simple nutrient enrichment algal bloom paradigm, and [data] suggests that there may be other factors contributing to the rise of cyanobacteria across Ontario aside from simply increased nutrient runoff.”
A great concern of blue-green algal blooms are their potential to produce toxins. Freshwater cyanobacteria produces four main groups of toxins: microcystins, anatoxins, saxitoxins and cylindro spermopsins, and variants fall within those broad groups.
“By far the most common toxin associated with freshwater blooms are the microcystins, which are hepatotoxic, or toxic to the liver,” said Favot. “In these broad categories here, not all species within them are capable of synthesizing toxins and, this one’s important, even if we know there’s a species that has the potential to produce toxins, it doesn’t always [produce them] and when cyanobacteria produces toxins or not, it likely depends on specific environmental conditions that we don’t understand yet, so for that reason a precautionary approach is taken where if there’s a suspected blue-green algal bloom we take a sample, we put it under the microscope, find out which species it is, and if it’s a species that we know has the ability to produce toxins, we assume that toxins could be present until the bloom dissipates.”
Favot said the first microcystin toxin was isolated and characterized in the 1980s, yet “clearly cyanobacterial toxins are a widespread issue despite being a relatively new area of research.” Health guidelines in place for microcystin are set at 1.5 micrograms per litre, total microsystems acceptable in drinking water in Canada, said Favot, and 20 micrograms per litre for recreational waters.
She noted the consequences of freshwater cyanobacterial toxins can be serious, citing the death of 60 patients in the 1990s at a Brazilian dialysis clinic, where water used for treatment was later found to be contaminated with almost 20 micrograms per litre of microcystins, and the shutdown of tap water usage for two days in Toledo – with a population of nearly half a million people – in 2014 due to microsystem concentrations exceeding the drinking water quality standards. The message to not drink water from or swim in lakes affected by algal blooms and to heed public health advice was reiterated by Favot as well as others joining her in a forum after the presentation.
“But it’s not all just about the potential for toxin production, there are negative consequences of both toxin producing and non-toxic blooms,” she said. “Of course blooms that produce toxins are a health risk to humans and animals, but whether or not blooms are toxic, the biomass produced during blooms reduces water clarity or increases turbidity, and this can lead to biodiversity loss, through a reduction in the growth of other photosynthetic aquatic organisms.”
“The increased turbidity or reduced water clarity associated with blooms also reduces aesthetic and economic value of the water body,” she said. “Bottom water oxygen depletion, which is associated with the end of blooms when excess organic material is being decomposed, can reduce the suitable habitat available for certain aquatic organisms, and result in fish kills and can also exacerbate internal nutrient loading from the sediments at the bottom of the lake, which can then result in a kind of positive feedback cycle that can further bolster future blooms.”
While research is still occurring to help determine the complex causes of algal blooms, three main categories can be used to “conceptually organize the interacting factors that can lead to blooms,” said Favot: weather conditions that lead to warm and stagnant water, elevated nutrients due to both natural and human-caused sources, and food web alterations, or changes in algae consumption by upper food web organisms.
“The dreaded climate change can alter conditions across all three of these categories, to make conditions more favourable for blooms to occur and so it can be kind of thought of as a threat multiplier in the case of conditions that promote cyanobacterial blooms,” she said.
Favot also explained the process of thermal stratification in lakes; discussed her PhD research involving paleoliminology, a branch of lake science that examines fossil material in lake sediment to determine the environmental history of an ecosystem; her work on lakes in Ontario, enabling her to compare pre-disturbance conditions with today’s conditions, and the consequences of climate warming in making conditions favourable for blue-green algal blooms.
“The best thing we can do is try to prevent blooms from occurring in the first place and one of the easiest ways to do that is to minimize nutrient pollution running off from human activities in the catchment,” she explained. “And a very easy way to do that is to intercept nutrients running off the land with terrestrial plants which can sequester these nutrients before they reach the lake. There will always be ecological surprises especially since there are so many interacting factors that can lead to blooms but I do believe that with further research we will be able to pinpoint specific lakes that may be most sensitive to developing future algal blooms, and maybe a good start to that is to look towards lakes that have moderate nutrient levels or are classified as mesotrophic and lakes that are relatively shallow so that low oxygen conditions develop rapidly with thermal stratification. Lastly, I found that bottom water oxygen and nutrient concentrations indicating the occurrence of internal nutrient loading, might be more useful for determining the potential for blooms than surface water concentrations and so for groups that have the means we should try to incorporate oxygen profiles or a bottom water chemistry sample into our monitoring programs. So while it takes a lot of highly specialized work and time, understanding environmental histories is the key to putting current water quality issues into context and establishing baseline conditions is critical to inform management targets for parameters like nutrients.”
“Cyanobacteria are among the most ancient organisms on earth and when they’re in balance with the rest of the ecosystem they’re an essential and beneficial component,” said Favot. “However, blooms or excessive growth of certain species of cyanobacteria can have very negative ecosystem level impacts and unfortunately we expect that with continued climate change, blue-green algal blooms will become increasingly frequent and severe moving into the future.”
The presentation included a forum with Professor Barb Elliott from Fleming College and Dr. Norman Yan, research scientist, and a question-and-answer period from the audience.
To watch Favot’s presentation in full, visit environmenthaliburton.org.
For more information about the Lake Partner Program and how you might help by monitoring your lake, visit Environment Haliburton’s website at https://foca.on.ca/lake-partner-program-overview/.
Environment Haliburton’s next Enviro Cafe will be held virtually, via Zoom, on March 9 at 7:30 pm.