Overview and Explaination
Lake Winnipeg
Lake Winnipeg is one of the largest and most important watersheds in Canada. However, recent massive blooms of blue-green algae have put the lake in jeopardy. These blooms can cause dangerous levels of toxins that threaten the health of fish and other organisms, as well as livestock and humans. The cause of these blooms is nutrient loading and eutrophication. Excess phosphorus and nitrogen from agricultural fertilizers, and pollution from sewage treatment plants and septic tanks are creating a nutrient rich Lake Winnipeg, enabling the algae to thrive. The blue-green algae have already created an oxygen deficiency in the lake that can cause a collapse of fish stocks and other important ecosystems. If remediation and education practices are not put in place quickly, Lake Winnipeg will become an uninhabitable, toxic swamp.
Research on Lake Winnipeg
Until 1998, when the Lake Winnipeg Research Consortium (LWRC) was formed to do research in multidisciplinary areas on a regular basis in Lake Winnipeg, very little research had been done. There had been only two studies, one in 1930 and one in 1969, which examined several aspects of the lake at once (LWRC, [PC], 2003). In 2002 the LWRC began a research project which collected data three times a year. Their goal was to get a detailed look at the variability of physical, biological and chemical components of Lake Winnipeg. The LWRC survey examined several different aspects of Lake Winnipeg.
At 65 stations located around the lake, sampling was done for phytoplankton (plant plankton), zooplankton (animal plankton) and benthos (bottom organisms). They also studied water chemistry and analyzed for suspended carbon, nitrogen, phosphorus, iron, chlorophyll and total suspended solids, dissolved organic and inorganic carbon, chlorides and sulphates, total dissolved nitrogen and phosphorus, conductivity, magnesium and pH. During inter-station travel of the research vessel, lake water was drawn continuously from near the surface by a submersed intake fixed forward of the ship’s bow. Parameters measured from these samples included pH, conductivity, surface oxygen, fluorescence, turbidity and pCO2 (partial pressure of gaseous carbon dioxide). At the approach to each station, fish, in particular rainbow smelt, were sampled with a 3m x 3m trawl alongside the vessel at 2 knots an hour for a period of 30 minutes. Surface plankton was simultaneously sampled using a 0.5m diameter plankton net (250 micron mesh) towed from the stern of the ship (LWRC, [PC], 2003).
The survey found that massive blue-green algae blooms in the northern basin could potentially cause Lake Winnipeg critical damage if remediation efforts are not taken. Several factors including nitrogen and phosphorus loading, an increasing lake temperature and thermal stratification are providing ideal conditions for the rapid expansion of the toxic blue-green algae (LWRC, [PC], 2003).
Causes of Lake Winnipeg Algae Blooms
Nutrient loading, or eutrophication, is the main reason blue-green algae blooms on Lake Winnipeg have been expanding at such a rapid pace. Nutrient loading is the addition of chemical nutrients in high concentrations that creates an enrichment of the ecosystem and an increase in plant and algae growth. Phosphorous and nitrogen are typically associated with the eutrophication process and are the two nutrients in Lake Winnipeg responsible for the blue-green algae blooms (Canada, Manitoba Phosphorous Expert Committee, 2006, pg 6).
Runoff from agriculture and development, and pollution from septic tank and sewage treatment plants are the two most significant phosphorus inputs into Lake Winnipeg (Canada, Manitoba Phosphorous Expert Committee, 2006, pg 6). “In the Canadian portion of the Lake Winnipeg drainage basin alone there are over 20 million livestock and 5.5 million people, 80% of whom are living in eight urban centres”(LWRC, [PC], 2003). This contributes a massive amount of pollution to the Lake Winnipeg watershed. Over 60% of phosphorus loading is attributed to the Red River (LWRC, [PC], 2003). A large percentage of this phosphorus comes directly from Winnipeg and the surrounding areas, whose sewage treatment and direct agricultural runoff all flow into the Red River.
In Lake Winnipeg nitrogen loading is split evenly between the three rivers, the Saskatchewan River, the Red River and the Winnipeg River (LWRC, [PC], 2003). Blue-green algae are unique in that they can process their own nitrogen directly from the atmosphere, known as nitrogen fixation. In Lake Winnipeg the algae form blooms when there is a much larger concentration of phosphorus in the water than nitrogen. The harmless green algae die off when the nitrogen levels in the water are not sufficient to grow, but since blue-green algae can take nitrogen from the atmosphere, they rapidly outnumber the green algae (LWRC, [PC], 2003). Phosphorus is being added to Lake Winnipeg through sewage-treatment plants, fertilizers and farmland runoff, causing such an imbalance in the phosphorus/nitrogen ratio that blue-green algae blooms have become a yearly occurrence. This fixation adds enormous amounts of nitrogen back into Lake Winnipeg, estimated to be 100 tonnes of nitrogen drawn into the north basin every 24 hours (Department of Fisheries and Oceans, 2004). The addition of this much nitrogen increases the growth of the blue-green algae, acting as a positive feedback system.
Also contributing to the eutrophication of Lake Winnipeg is the enormous silt load that the Red River dumps into the south basin due to the clay soil of the area. This silt load combines with the high turbidity and shallowness of Lake Winnipeg’s south basin, creating minimal light penetration and therefore low rates of photosynthesis. This restricts the blue-green algae to the north basin, where deeper, clearer water facilitates photosynthesis (LWRC, [PC], 2003).
Lake Winnipeg is a delicate ecosystem that needs an optimum balance of nutrients to function properly. Nutrient loading of phosphorus and nitrogen have enabled blooms of toxic blue-green algae to throw Lake Winnipeg out of balance. This will have consequences to the ecosystem of the lake and can potentially turn Lake Winnipeg into nothing more than a swamp. Not only are the algae blooms dangerous to animals and humans, they have an economic impact on fisheries and tourism, which provide thousands of people with sources of revenue. The future of Lake Winnipeg lies in the initiatives and efforts of the people who live in the surrounding watershed. It is important for everyone to take an active role in understanding the function Lake Winnipeg plays in our environment and the processes that affect its water quality. It is the government’s responsibility to ensure that the knowledge and tools to help prevent the toxic blue-green algae and improve the health of Lake Winnipeg is readily accessible. If efforts are not made soon to minimize the input of harmful nutrients that are causing the algae blooms in Lake Winnipeg, one of the most important ecosystems in Canada may die.
References:
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Canada. Lake Winnipeg Stewardship Board. (2005). Our Collective Responsibility: Reducing Nutrient Loading to Lake Winnipeg. Gimli: Lake Winnipeg Stewardship Board, January.
Canada. Manitoba Phosphorus Expert Committee. (2006). Recommendations for Regulating Phosphorus from Livestock Operations in Manitoba. Winnipeg: Manitoba Phosphorus Expert Committee, January.
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Lake Winnipeg Research Consortium Inc. (2003). Phytoplankton Nutrient Status. Retrieved October 14, 2006, from http://www.lakewinnipegresearch.org/sciencepdfs/PHYTOPLANKTON.pdf
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