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Indicator Type: Environmental Condition
Trophic status refers to the overall level of biological production in a lake. It is usually based on the total mass of algae. This mass is represented by the concentration of the plant pigment chlorophyll-a in water samples. The map shows the trophic status of Alberta lakes based on the average summer chlorophyll-a concentrations between 1983 and 2003.
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Trend: No clear trend
The four categories range from "oligotrophic" lakes that have very low levels of biological production, through "mesotrophic" to productive "eutrophic" lakes, and finally to "hypereutrophic" lakes that have significant algal blooms throughout much of summer and fall. For more information about these categories, see Trophic Status Categories.
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What does the indicator show?
Some Alberta lakes have only small populations of algae and large aquatic plants, while others have large populations. Water quality is sufficiently impaired by this growth in many lakes to limit their suitability for fish, recreation and drinking water sources.
Algae and aquatic plants require nutrients such as nitrogen and phosphorus for growth. To a large degree, concentrations of phosphorus are naturally elevated in many Alberta lakes. This is due to underlying sedimentary bedrock, thick glacial deposits, and soils within their watersheds being nutrient-rich. However, phosphorus can also increase as a result of urbanization, industry and agricultural practices.
To see charts of biological production in the Alberta lakes shown in the map, based on both chlorophyll-a and total phosphorus, click here.
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Why is this indicator important?
Lakes are important for their scenic and recreational values. They also serve as sources of water for drinking and industrial use. As well, many lakes support important commercial and sport fisheries. Trophic status or the degree of biological production within a lake is a key biological component of water quality. Lakes with low levels of biological production are often clean and clear, supporting small fish populations. As biological productivity increases, algal blooms may occur and the water can become murky. Decomposition of plant material can use up oxygen and stress the resident fish.
In lakes where biological productivity is extremely high, water quality can be impaired to the point where some recreational activities may not be advisable. These activities include swimming and water-skiing, where there is direct contact with the water. As well, treating drinking water from such lakes is difficult and costly.
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What actions are being taken?
The Alberta government has monitored lake water quality since the 1940's. Today, several programs aim at monitoring water quality in Alberta's lakes. These include the Long-term Lake Network and the Provincial Parks Lakes programs. In addition, the government supports and works with the Alberta Lake Management Society. The society is a non-profit organization formed a decade ago. Its goal is promote understanding and good management of Alberta's lakes, reservoirs and their watersheds. Together, the government and the society actively monitor water quality at many of Alberta's more popular lakes. The government and the society have played a key role in addressing concerns regarding lake water quality and particularly the issue of eutrophication.
The Pine Lake Restoration Project is a prime example of how government and stewardship groups can work together to manage and improve water quality. The project successfully reduced the amount of phosphorus entering and staying in the lake. This is expected to result in decreased algal growth, clearer water and an overall improvement in water quality. To download a copy of the initial results of the Pine Lake Restoration Project, visit the Alberta Environment Information Centre.
The Water for Life strategy represents the provincial government's most recent commitment to ensuring Albertans have safe, sustainable water supplies for communities, the economy and the environment. Trophic status is a key aspect of lake water quality and is addressed in the strategy.
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Links to additional information
Surface water quality in Alberta - Alberta Environment: http://www3.gov.ab.ca/env/water/SWQ/index.cfm
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Feedback
E-mail the SOE Coordinator: SOE.Coordinator@gov.ab.ca or complete this short on-line questionnaire to provide your feedback: http://www.zoomerang.com/
survey.zgi?p=WEB224DW6P3E2K.
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