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Severn Sound Water Quality |
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Severn Sound has experienced
excessive phosphorus enrichment since the 1960s. This resulted in
excessive algae growth, leading to poor water quality conditions for
recreational uses such as swimming, and low oxygen conditions for cold
water fish communities.
In 1985, Severn Sound was listed as an Area of Concern (AOC), one of
the most polluted on the Great Lakes.
Led by Environment Canada and the Ministry
of the Environment, the communities surrounding
Severn Sound developed a Remedial Action Plan (RAP), the goals of which
were to improve water quality and restore a
healthy ecosystem in Severn Sound. Over
the past 20 years, implementation of the RAP resulted in reduced
phosphorus loads through sewage
treatment plant upgrades, agricultural projects, private sewage system
upgrades, and stormwater treatment. This in turn led to significant
improvement in the water quality of
the Sound. In 2003, restoration targets had been met, and Severn Sound
was delisted as an AOC. The RAP continued as the Severn Sound
Environmental Association (SSEA),
which monitors 11 stations throughout the Sound in an effort to detect
long-term changes in water quality. SSEA continues to monitor water
quality and work with municipal
partners to ensue that the quality of Severn Sound is maintained.
These are essential for
growth and reproduction of living organisms. Two key nutrients are
phosphorus and nitrogen. Although naturally found in the environment,
excessive amounts create imbalances in plant
and animal communities and adversely affect our water use. Phosphorus is
the most limiting nutrient for plant growth, so increases
will lead to increased algal densities. Phosphorus concentrations have
decreased below the target of 15 μg/L for Severn Sound and 20
μg/L for Penetang Harbour. Reduced
phosphorus loads from upgrades to sewage treatment plants, agricultural
projects, private system upgrades and stormwater is also an important nutrient for plant growth. Sources can be
both natural (air and soil) and
anthropogenic (fertilizers, animal and human waste). Nitrate, the form
of nitrogen most available to plants, has been increasing since 1970.
Measured using a Secchi
disc, this is a measure of the amount of particles (sediment
and algae) and colour in the water column. Over the last decade, clarity
has increased at all stations and target
levels of 3 m for Severn Sound and 2 m Penetang
Harbour have been
related to lower water levels in Georgian
Bay-Lake
Chlorophyll This pigment is found in
both plants and algae and relates to the amount of algae
in have decreased, reaching target levels of 5
μg/L for Severn Sound and 7 μg/L for Penetang
Harbour.
These microscopic plants
grow suspended in the water column. Population densities
can vary throughout the season depending on light, temperature, and
nutrient availability. The right combination
of these factors can result in algal blooms,
which may affect the taste and odour of drinking water, and cause beach
fouling. All stations have shown a decrease
in the total biovolume of algae.
Zooplankton These microscopic animals
live suspended in the water column. algae
Despite normal annual fluctuations,
the number of zooplankton species, or diversity, has increased, a
healthy sign. Zooplankton help keep algal
populations in check through their grazing
activities. |
