Discovery Club members wondered about the water quality of the water in the lake at Patrick Marsh. One of the easiest measurements is water temperature. We wonder how does human activity effect water temperature. We do know that warm water holds less oxygen then cold water and when water gets too warm it is bad for fish

Fish need oxygen to breathe. There are a number of factors that control the amount of oxygen in Patrick Marsh. Oxygen levels increase by wave action or from the photosynthesis of Algae. However, when Algae die they are decomposed by bacteria which consume oxygen. When dissolved oxygen get below about 3 ppm, fish can't live. Dissolved oxygen levels in water are very hard to measure by chemical methods. We were lucky Mr. Gilbert Williams, the chemist at the Sun Prairie Waste treatment plant, was kind enough to lend us a spare oxygen meter. This picture shows how we had to put waders on to measure oxygen levels.

The Secci Distance measures the level of suspended particles in the water. These come from erosion or excess phytoplankton (algae). A clear lake can have Secci distances of many feet, but lakes with a lot of algae can be just a few inches. A circular disk attached to a rope is lowered in the water until it can't be seen and the rope is marked at the level of the water. The distance between he disk and the mark is the Secci distance

Nitrates can act as fertilizer and cause algae growth which can lower oxygen when they rot. Too many nitrates can be toxic to fish. Nitrate levels should be below 0.5 mg/l 5. Phosphates can also act as fertilizer and lower oxygen. Phosphate are not toxic except at extremely high levels. We sampled the water and measured nitrate and phosphate using chemical-colormetric methods