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BLUE-GREEN ALGAE: THEY ADAPT, THEY MULTIPLY & CAN BE DEADLY
An interview with Environment Canada Research Scientist, Sue Watson. - Part 1
Sue Watson is a research scientist at Environment Canada specializing in algal outbreaks and source-water impairment. Water Today spoke with Dr. Watson over the phone, this is PART 1 of the transcript of that conversation.
WaterToday: Not all blue-green algae or cyanobacteria are toxic. Could you tell me a bit about what your research taught you about blue green algae?
Dr. Watson: Let me first clarify that blue-green algae are in fact very misnamed. It's the very old term we used to use for these organisms because they carry a pigment that gives them at times a blue green appearance; especially when they die and release this pigment in the water.
In fact although they behave like true algae, in many ways they are like plankton. They can use the sun's energy to fix carbon and fuel their growth, through photosynthesis. All blue green algae - as they used to be called - are bacteria, and they have the same capacity to drive their growth by using the sun's energy. But although they behave very much like algae, real algae are much more closely related to plants.
Without going into the details of the differences in terms of the cell structure, one of the most apparent ones is that all plants and higher organisms have what we call sexual reproduction, whereas cyanobacteria and all other bacteria just divide; most often, they don't need to change genes which means they can divide very rapidly. So these organisms are very specialized in lots of different ways.
For example, in Lake Superior and some of the very far Northern lakes, which are reasonably or completely undisturbed, cyanobacteria are some of the main organisms that are actually fuelling the lakes. They are present as these tiny, tiny little cells called 'picocyanobacteria', about the size of 1 or 2 microns, and they are extremely, extremely valuable. They are the energy intake for the lakes which drives the entire food web.
WaterToday: Do you find these picocyanobacteria only in Northern lakes?
Dr. Watson: No, picocyanobacteria are really, important in many of our lakes, in fact if you look across every single lake in the world you will find cyanobacteria everywhere. They're also probably in most soil types, and present in many terrestrial systems where they act as a sort of factory for energy, you know, the solar panel for the lichens.
WaterToday: So we shouldn't bad name all of them?
Dr. Watson: No, because some of them are extremely, extremely valuable. Their ability to fix nitrogen, on the root nodules of legume or rice plants for example, is what fixes a lot of nitrogen into the soils.
But just like all other organisms there is a large variety of them, like plants for example. Plants come in all shapes and sizes, and we call some of them weeds because they can spread very quickly, taking advantage of damaged areas, where a fire occurred for example; cyanobacteria have the same sort of capacity.
Like weeds, there are species of cyanobacteria that take over at times when the systems are stressed, and those are the ones we worry about most. Because of late many of our systems have become more and more stressed, or enriched by all the nutrients (especially phosphorus and nitrogen) we've been pouring into them.
WaterToday: Let me go down that road a little bit. If these are such cool little organisms how come we want them dead when it comes to Lake Erie?
Dr. Watson: What we're trying to do is make the environment less favourable for the growth of the ones that are potentially harmful or a nuisance; those species that are able to develop rapidly. Those have large cells, grow in clumps, chains or bundles, and develop to such a high abundance that they can extend over much of a lake's surface, as you see for example on the satellite images of Lake Erie, Lake Winnipeg and Lake of the Woods.
WaterToday: Those images were pretty alarming...
Dr. Watson: And those are the ones that we want to keep out of our lakes or at least at very, very, lower levels. You're not going to eradicate them, once present, they will most likely always be there. But to keep their levels down we need to keep conditions such that they cannot spread rapidly.
Meanwhile the tiny picocyanobacteria are very good at living at low phosphorous levels and in unstressed environments. So as much as possible, we want to bring the lakes back to the condition that would favour that sort of a balanced food web that deters 'weed-like' cyanobacteria from taking over.
WaterToday: Let's talk about Lake Erie since it is one of the most affected by blue-greens. It had rebounded from earlier issues if I am not mistaken?
Dr. Watson: Yes. We have a Great Lakes Water Quality Agreement that was first signed in the early '70's when Pierre Trudeau and Richard Nixon were leaders of Canada and the US, and when everyone had finally woken up and said, My, look at these Great Lakes, they're in a real mess. And they were.
These ecosystems were severely affected by humans, partly because they had been receiving significant quantities of discharges from untreated sewage and industry and partly because of phosphates in detergents, all of which were favouring the development of large algae blooms.
And so both sides of the Canada-US border were put on a 'phosphorous diet', so to speak, and slowly they bounced back and regained some of the healthier aspects of the ecosystem. And the number of blooms was very much reduced. They did not disappear completely but they were much less frequent. Blooms will occur every now and again anyway, even in the middle of nowhere for no apparent reason. They just seem to 'pop up'.
WaterToday: We've noticed that lakes that don't have houses around them or lots of farms or anything suddenly have blue green. So that could just be a natural occurrence, could it?
Dr. Watson: Yes, in fact we have reports going back to the 1800's of the North area of Lake of the Woods - which at the time I think had very few (or no) houses on it - very occasionally getting short-lived blooms which would then go away. It's when they become recurrent every year and become really widespread that blooms are a real issue.
Having said that, some waterbodies receive a fair amount of natural nutrient loading from the watershed; it's released slowly from the soil. You may also get chance events, for example, from storms and floods, or a large dieback of vegetation that releases phosphorous. And they're natural.
WaterToday: I have to say I didn't know that. I always thought this whole thing had been man-created.
Dr. Watson: Oh no! Cyanobacteria evolved long before we were even thought of and they'll likely be here long after we've gone. So they've had lots of time to develop some very clever adaptations. Considering they're bacteria, they're amazing organisms!
Many of them are multi-cellular. In other words they're not just one cell floating around; they float around in bundles, chains, or aggregates, and this allows them to do more. It allows them, for example, to escape from the little water fleas and some of the other little micro-organisms which would normally eat all single cells.
WaterToday: I like this dieting analogy. Let's go back to the Lake Erie blue-green explosion. From your point of view what's created these new monster blooms as of late?
Dr. Watson: Well, once the lakes had recovered after that first initiative with the Great Lakes Water Quality Agreement, a lot of the monitoring was stopped. We became complacent; meanwhile there was a tremendous upswing in agricultural development and a lot of the crops were changed over to 'cash crops' which are very fertilizer-hungry. Unlike traditional family-owned farms where the soil was looked after to ensure that there was very little erosion, with tenant and large industrial mega-farms there is less incentive for long term stewardship and soils are becoming less and less able to support the crops, so more intense application of fertilizers can be required.
There are all kinds of other reasons why the significance of agricultural nutrient input has risen substantially. Most notably there has been a shift from a predominance of 'end of pipe' wastewater nutrient inputs - which can usually be identified and managed by improved waste treatment - to a predominance of inputs from all along the edges of the fields and particularly where there's tile drainage.
This makes it very difficult to identify and manage the sources that is, to say it's this farm or that farm; or it's this kind of crop or that kind of crop because it's such a patchwork of inputs. And it varies with soil types, it varies with crops, it varies according to farming practices and it varies very much with weather: some years we get a very severe freeze; some years we get very rapid spring run-off and all that contributes to this very difficult and very challenging problem of trying to identify where the major sources of fertilizer run-offs are.
WaterToday: If I understand you correctly nitrogen and phosphorous are the basis of most fertilizers and there's been far too much of these elements dumped on the fields?
Dr. Watson: Correct. For example, some farms may not check the soil first and see what it needs and just assume that it needs this specific amount and it gets applied. But plants only take up what they need, and if there's any leftover it will just get washed off the land.
WaterToday: So then this extra fertilizer so to speak runs off into tile drainage?
Dr. Watson: Well it runs off depending on the soil capacity; if you have a very healthy soil with good amounts of organic material, it will act to some extent like a sponge and hold some of these excess nutrients. But the thinner and less well-tended the soil is, the less 'carrying capacity' it has. And a lot of fertilizer just gets washed away. As for tile drainage, it's a system of drains lined with tiles which is built to drain properly and carry water away. In fact what that does is expedite the loss of nutrients in these areas.
WaterToday: I had no idea. Let's continue this then, so all of this extra phosphorous and nitrogen runs off into the lake and then what?
Dr. Watson: Let me explain a bit more about these particular organisms, cyanobacteria, and why they're so good at what they do. They have all sorts of adaptive mechanisms, basically 'tricks up their sleeves'. For example, they have tiny gas vesicles (a bit like fish bladders), that allow them to move up and down on the water column and adjust themselves to the right light and nutrient levels.
Cyanobacteria don't necessarily stay on the surface, all the time, if it's really hot and there is a lot of radiation from the sun, they will move down in the water column. Or form a massive slick which can be seen floating along the edge of the water in the morning, as if it grew overnight. Well, it didn't grow overnight! The cyanobacteria were already present before this, growing deeper in the water column. Under low light conditions or when gets dark, the gas vesicles inflate and the cells moved up to the surface. This allows them to access more light. On a wind-free morning, this allows the formation of a scum of cells.
So that's one of the mechanisms but they have all kinds of other 'tricks'. For example, they have these special 'organelles' or bodies inside their cells which allow them to take up extra phosphorous or nitrogen and save it for when the exterior supply is depleted. Just like we put food in a pantry to save it for 'rainy days'.
Another thing they do is produce a large number of biologically active compounds to engage in a very active chemical warfare. Some of these cause objectionable taste and odour in drinking water (but don't harm you), others are toxic, and those are the ones that we're more immediately concerned about. They are toxic towards humans and animals, including pets and livestock.
WaterToday: We've done a couple stories where lakes had blue green and unfortunately some pooches were, well they're not with us anymore.
Dr. Watson: Well the reason usually is because pooches and cattle are less discriminating and not so fussy about what they drink; or for example dogs will go and play in the water and then they'll come out and lick their fur.
WaterToday: That's what happened to this guy, he had a pair of dogs and his lake went blue green; never thought it over, played with the stick, and the dog dropped dead.
Dr. Watson: There are several types of toxins and they each have different effects on organisms. Some of them are what we call neurotoxins. And those are very rapid - if you ingest too much of them you die by suffocation because your breathing apparatus is paralyzed. The other types are what we call liver toxins ('hepatotoxins'), and the toxin that we hear about the most in North America, called 'microcystin'.
WaterToday: That's the one that caused the Toledo crisis, right?
Dr. Watson: Yes. If you drink too much of that one, it will produce massive liver haemorrhaging and death. Then there is what we call the sub-acute effects of these different types of toxins. For example, some the of liver toxins are also known to be carcinogens. Let's say you have a cottage on a lake and you've got a very rudimentary water filter that doesn't take care of all the toxins in the water, the toxic levels may not kill you but you are more likely to develop a higher risk of having some form of GI cancer.
BLUE-GREEN ALGAE: HOW THEY THRIVE IN OUR OVERFED AND INVADED LAKES
Toledo after the slime - The crisis, the causes, the roadblocks to a fix
400,000 TOLD NOT TO DRINK OR BOIL TOLEDO WATER, OH - Today Dailies 8/2/14
Experts comment on Toledo - 8/3/14
Blue-Green Advisory Map - Canada
Blue-green advisory list per province - Summer 2015