This is an informal attempt to answer some of the questions about algal blooms
on Simon Lake. I believe it is accurate, but I would advise consulting the Health Unit or the Ministry of the Environment
for authoritative information. Water quality information is also available on the City of Greater Sudbury website at
www.greatersudbury.ca. Please regard this as a personal interpretation of the situation.
Q. Are the algae in Simon Lake Harmful?
As far as I am aware the algae that have been identified in Simon Lake in previous
years have been "green algae". Two kinds have been especially tolerant of metals like copper dissolved in the water.
Green algae are plants. They are not known to be a direct threat to human health. Their impact is aesthetic and
environmental through smothering of shallow water habitat and consumption of oxygen. In October when the mat rots it
produces chemicals with a strong smell, especially phenols. I am not aware of "blue-green algae" (which are bacteria
- not algae) having been identified. It is certainly possible they are present. Some blue algae release toxins
from their cells when thy die or rupture, which can damage liver and nerves if they are in drinking water. Animals are
more likely to be affected by "blue green algae" than people because animals are less discriminating about the appearance
of the water they drink. So it is best to keep pets out of the lake. "Blue-green algae" may also be the cause
of swimmers itch.
Q. What is the cause of algal blooms in Simon Lake?
Green algae, like other plants, grow best in fertilized conditions. The most
important fertilizing ingredient is phosphorus. Phosphorus gets into lakes naturally. In Canadian Shield lakes
the content of phosphorus is about 4 or 5 parts per billion. In Simon Lake, the phosphorus is much higher.
There are many sources of the phosphorus in Simon Lake. However, much of it can be traced to poor sewage disposal in
the distant past. Kelly Lake is upstream of us, and it was Sudbury's sewage lagoon until 1972. I have been told
by long-time residents tat outhouse "muck" was dumped in Junction Creek near Copper Street park and raw sewage was discharged
into Junction Creek near Martindale Rd. Junction Creek also received the outflow of the City's sewage drains as they
were being constructed. Today, waste water continues to be discharged upstream of us. It is still a source of
phosphorus, but the upstream sewage treatment plants all have phosphorus removal systems. However, the old sediment
in the creek and downstream lakes still contains phosphorus from the pretreatment plant days.
Q. Why were algal blooms not worse on Simon Lake before the Sudbury sewage treatment
plant was built?
It is likely (but not proven) that prior to the 1970s when quality controls were placed
on mine water discharges, the high copper concentrations from mine site water that drained into Kelly Lake acted as an algicide,
killing algae from Kelly Lake downstream to McCharles Lake.
Q. Why do Simon Lake's recent algae blooms seem to be worse than most people can remember?
It is likely that the 2007 bloom (the worst I have seen since 1978) can be linked
to two reasons:
- The Spring run-off was low and there was little rain to supplement the melting
snow. As a result a good deal of the phosphorus that had leaked into Simon Lake during the winter under the ice was
not flushed out.
- The lake was warmer than usual by about 5C. Last summer, we measured water temperatures
of 20C at the surface and 15C at a depth of 7 metres. This warmth encourages decay of organic matter in the sediment,
coumption of oxygen at the bottom and leakage of phosphorus tends to mix throughout the lake. The result is an unusually
productive summer phosphorus source at the bottom of the lake, followikng a Spring of little flushing of phosphorus-rich winter
water. It might be that the Spring of 2007 was exceptional. On the other hand we know that climate is changing
and models suggest they will become typical - shorter winters with a thinner snow pack followed by a weak Spring melt and
warmer Summer.
Q. What can be done?
Raking or gathering up the algae is probably hopeless because it will grow back very
quickly. Furthermore, it only deals with a symptom of the problem not the cause. The most effective way to control
the algae is to lower the phosphorus levels. In my opinion, what we know of the lake strongly suggests that phosphorus
is being produced in Simon Lake rather than being brought in from upstream.
In some countries alum (aluminum sulphate) is added to the water of phosphorus rich
lakes. The result is that the chemical combines with phosphorus to quickly make a gel on the floor of the lake.
However, that is not permitted in Canada because of environmental and health concerns.
Hamilton Harbour and some lakes with contamination problems of various kinds have been
dredged. If the organic muck was dredged from the bottom of Simon Lake it might be possible to dispose of the sediment
on the Copper Cliff Tailings. Dredging would have to be done very carefully but modern dredging technology is much more
sophisticated than it used to be.
Aearating or oxygenating a lake discourages the release of phosphorus from the sediment.
Oxygenation can be done by pumping oxygen or air into the water, or mechanically mixing the lake water so it doesn't separate
ino an upper well oxygenated layer and a poorly oxygenated lower layer. However, it would be hard to do effectively
in Simon Lake because phosphorus is leaking from everywhere, not just a few deep spots.
