Quinte waters in the broader context of the Great Lakes

An examination of of some historical and contemporary aspects; shipping and the environment [*]

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The Problem:

Example of eutrophication [click image to enlarge]

      Eutrophication is the scientific term for nutrient enrichment. The large amounts of phosphorus in the Bay lead to excessive algal production, of which the effects include; reduced oxygen levels, reduced water clarity and bad smelling/tasting drinking water. As a result of these changed conditions, foreign species begin to inhabit the area. Phosphorus pollution was noted as being serious in the 1930s.

The main source of phosphorus pollution is discharge from sewage treatment plants. Sewage goes through a primary treatment, where it passes through screens and shredders into a settling tank, forming ‘sludge’. Sludge is mainly composed of human, industrial and household waste, though it may contain numerous chemicals dumped illegally into the sewer. Secondary treatment bacterially removes most of the solids and carbon, so the organic matter becomes inorganic. After the secondary treatment, sewage does not carry disease or offensive odour, but it still contains phosphorus. Originally, raw sewage was dumped into water and for most of the 20^th C. sewage treatment plants only employed primary treatment. From 1940-1960, six sewage treatment plants were built around the Bay of Quinte area, and all of them dumped their treated sewage into the Bay. In 1965, 215 kg of phosphorus was entering the Bay of Quinte per day as a result of sewage. In 1970, the IJC blamed excessive phosphorus as the root cause of Great Lakes eutrophication.

Prince Edward County; areas affected by sewage treatment [click image to enlarge]

Agricultural runoff can also be blamed for high phosphorus levels in the Bay of Quinte. Runoff is comprised of pesticides, fertilisers, manure and sediments, often containing high levels of phosphorus. Phosphorus from agricultural runoff can be a concern if it seeps into groundwater. Nitrogen is also capable of increasing eutrophication in large amounts, but it is vital in maintaining a balanced lake environment. An optimally balanced lake will have a ‘Nitrogen to Phosphorus’ ratio of 10:1.

Different marine species tend to overtake eutrophied areas, because they prefer the shade that extra algal growth can provide. In the 1950s, walleye became the new pre-eminent fish in the Bay of Quinte because they prefer the shaded areas with high algal density. But high algal density also limits macrophyte production, meaning the walleye’s food source was drastically reduced. As a result, walleye populations decreased. In 1955, piscivorous (fish-eating) lamprey overran the Bay of Quinte. The lamprey flourished and did serious damage to the Bay’s fish population, so the Great Lakes Fisheries Commission undertook a program to control sea lamprey in 1954. The program was successful and the lamprey population was reduced by 90% after the use of chemical lampricide 3-trifluoromethyl-4-nitrophenolin (TFM) in the1970s. Soon after, non-native white perch replaced lampreys as the Bay of Quinte’s dominant piscivorous species. White perch consumed many of the Bay’s algae-grazing fish, which was counterproductive to the water’s eutrophication problem. In 1978, there was resurgence in walleye and a collapse of the white perch population, coinciding with a major reduction in phosphorus output from sewage treatment plants. Algal density has been declining in the Bay of Quinte as a result of the renewed Great Lakes Water Quality Agreement, but still not enough to promote species diversity.

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* [back] - This project was developed by Isabel Slone (one of the Society's 2007 "summer students") and was in part funded with a grant from Young Canada Works, in part with a grant from the Municipality of the County of Prince Edward, and in part with this Society's research funds.