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Background
In the past, Severn Sound experienced excessive phosphorus enrichment. 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.
Monitoring in the open waters of Severn Sound began in 1973 by the Ontario Ministry of Environment. Five stations were regularly sampled, one in each bay of Severn Sound, and one in the open waters. In 1997, the Severn Sound Remedial Action Plan (now SSEA) took over regular monitoring, which continues today.
SSEA’s Open Water Monitoring Program monitors the environmental quality of Severn Sound open water for indicators of eutrophication. The Severn Sound RAP Stage 3 Report called for continued monitoring of open waters of Severn Sound in order to assess changes in trophic status in relation to remedial actions and other ecosystem changes in the area (e.g. invasive species, water level changes).
Sampling Method
Eleven open water stations are sampled biweekly during the ice-free season. Samples are taken throughout the euphotic zone at each station (2x Secchi disk depth) and are analyzed for nutrients, including total phosphorus, total ammonia, total nitrate, and total Kjeldahl nitrogen, as well as chlorophyll a. Zooplankton and phytoplankton samples are also taken. Water clarity is measured using a Secchi disk, and vertical profiles of temperature, dissolved oxygen, and conductivity are taken (surface to 1m off bottom).
In addition to the eleven Severn Sound Open Water Monitoring Program stations,
SSEA monitors long term at three stations around Honey Harbour and seven
stations on Lake Couchiching.
View
the SSEA Monitoring Station Map....Look for the black triangle
symbols
Significance of Water Quality Parameters
Total Phosphorus – this is a measure of the concentration of organic and inorganic (e.g. bound to sediment) forms of phosphorus in the water. Lakes are considered eutrophic, or enriched, at values over 30 ug/L.
Total Ammonia, Total Nitrogen, Total Kjeldahl nitrogen – these measure various forms of nitrogen. Ammonia and nitrate are highly available to plants and algae, and tend to be used up quickly, leading to a sharp decline in concentration between spring and fall. Total Kjeldahl nitrogen in an organic form.
Chlorophyll a – this is a pigment found in all plants and algae, and the amount in a water sample is related to the amount of algae in the water. Values over 5 ug/L indicate eutrophic conditions.
Secchi disk depth – this is a measure of the water clarity, which can be affected by sediment or algae in the water. “Tea” coloured waters can also have low clarity due to the tannic acids leaching from nearby wetlands. The target for Severn Sound is 3 m, and 2 m in Penetang Harbour.
Temperature – temperature regulates many chemical and biological processes, from algae production to dissolved oxygen concentration, and it important to measure to give context to water quality results.
Dissolved Oxygen
– fish and aquatic insects require adequate levels of dissolved oxygen to survive. Low oxygen levels in bottom waters can be a symptom of eutrophication, and can lead to fish kills.
Conductivity – this is a measure of the amount of dissolved matter in the water. Generally, waters originating from the Precambrian shield (e.g. Honey Harbour) have low conductivity, while waters originating from limestone based regions (the majority of Severn Sound) have higher conductivity. Extreme values indicate a source of pollution.
Factors Affecting Water Quality
Severn Sound is a dynamic system that is influenced by the Great Lakes system (e.g. introduction of invasive species like zebra mussels and Bythotrephes, fluctuating water levels) and its surrounding watershed (point and non-point additions of nutrients and other contaminants).
Trends in Severn Sound Water Quality...
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