Toxic Algae in Lake Erie






While enjoying a beautiful Autumn afternoon at Clearville, 30 km East of Blenheim, 
on lake Erie, I was surprised to hear the sound of
approaching sirens. Expecting an out of control campfire I was
surprised to learn that emergency services had been called because of
the color of the water. Someone thought that the deep green, was a
result of a toxic chemical spill. Understandable in light of the
color, that of green paint, and the smell, somewhat sickening and
acrid.
What appeared last Saturday along most of the North Eastern coast of
Lake Erie was a bloom of toxic blue-green algae called Microcystis.
This bloom was the worst ever seen and is one of a number of stages
that indicate impending ecosystem collapse in many parts of the lake.


Over the past 80 years, our lake has seen an increase of algae which
is an indication of increasing phosphorus and nitrogen being released
into the lake. By 1960, Erie had been pronounced "dead" as large areas
of algae would die, rot using up the oxygen in the water. In the early
1970's Canada and the U.S. agreed to reduce the amount of phosphorus
being dumped into the lake, and for 20 years or so, large algal blooms
seemed a thing of the past. Gradually though, with the advent of
industrial scale farming and increasing urban populations, phosphorus
levels began creeping back up. Then came the zebra mussels.

Inadvertently introduced into our lake in the 1980's, zebra and quagga
mussels have, over the past 2 decades, colonized most of the shallow
rocky outcroppings of the western basin. Why is this important? Zebra
mussels and their close cousins are filter feeders and primarily eat
algae. That is, except for Microcystis, which the little mussels spit
out, by the billions. As it turns out, there are so many mussels in
western Lake Erie that they have an active role in increasing blue
green algae by eating the competition and changing the water chemistry
with their waste, increasing the nitrogen and phosphorus.

This year, along with extensive coverage of the western basin, west of
Point Pelee, a 2 to 4 km wide band of Microcystis extended along the
northern shore from Wheatley past Patrick Point at Duttona Beach in
West Elgin. Had this been swimming season, our beaches would most
certainly have been closed and warnings issued. Fortunately, this is a
seasonal event and the algae is on the move, Eastward. For the most
part, Microcystis prefers the surface waters but has the ability to
control it's buoyancy to avoid intense sunlight or to feed in cool
nutrient rich waters.


What makes Microcystis toxic is a cyanotoxin called, microcystin which
is part of the same family of chemicals responsible for red tide
shellfish poisoning. In mammals it damages the liver and is
cumulative. If one were to eat or drink some quantity of the algae, or
eat a filter-feeder that feeds on Microcystis then a trip to the
hospital would be recommended. The amount of toxin in the algae can
vary greatly and is increased by sunlight. Municipal water treatment
is effective in removing algal contamination.

All that said, our Lake is sending us a powerful message. These wild
population swings are the direct result of unchecked human activity.
Stopping Agricultural and Urban pollution is something that we can do.
So is preventing invasive species. The lake can and will heal, if we
just let it.

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