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A cluster of Merismopedia elegans
algae.
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Alga diversity is an excellent
indicator of water quality. When a river's water quality is good, the
species of algae that live in it will be diverse.
During the Rideau
River Biodiversity Project more than 300
species of algae were observed in the Rideau River. Most of these
species belonged to the cryptophytes group, which are organisms that resemble
diatoms
and occasionally sport flagella. The presence of numerous species of cryptophytes,
over and above the general diversity of the algae, is a sign that the
water quality is basically good.
Algae were particularly diverse in the wetlands around
Merrickville and Smiths Falls.
Algae are also able to tell us about the amount of fertilizer
(phosphorus and nitrogen) in the water. In effect, the proliferation
of certain species of algae indicates an abundance
of fertilizers.
For example, during the Project,
phosphorus levels and algal density were high within the City of Ottawa.
Large floating mats of decaying algae were visible along the shorelines.
This is a common site along many urban Ontario rivers.
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Masses of algae near shore, near Manotick.
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Not really. Algae are a normal and essential
part of a healthy river ecosystem. However, when there is too
much phosphorus in the river, the algae proliferate excessively,
and thereby place disproportionate pressure on the ecosystem.
After algae die they decompose while floating
on the surface. Even large clusters do not harm plants or
animals (humans included), but they return little benefit
to the river and interfere with some recreation activities.
In extreme cases, the decomposition of
the algae causes anoxia, which is an insufficiency of dissolved
oxygen in the water. This phenomenon, which can be fatal
to sensitive species (such as those species of fish that happen
to be sportfish), occurs in only a few places in the River.
To eliminate the algal masses from the
Rideau River, phosphorus levels must decrease. Discover how
you can contribute to this reduction.
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Sampling algae in springtime.
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