Sometimes eutrophication can happen naturally without any real cause. Sometimes when there are periods of heavy rain, the increase in rain water leads to an imbalance in the pH of the water. This in turn creates favorable conditions for the phytoplankton to grow and proliferate. This is a natural cycle that also ensures that too many fish and other animals do not build up in a freshwater source. This type of bloom is nature’s way of eliminating overpopulation with an abiotic factor. Although many organisms will die as a result, it will help to thin the numbers of organisms and ensure a healthier freshwater source.
In the 1960s and 1970s, Lake Erie was the most publicized example of eutrophication. Called a "dead lake," the smallest and shallowest of the five Great Lakes was swamped for decades with nutrients from heavily developed agricultural and urban lands. As a result, plant and algae growth choked out most other species living in the lake, and left the beaches unusable due to the smell of decaying algae that washed up on the shores. New pollution controls for sewage treatment plants and agricultural methods by the United States and Canada led to drastic reductions in the amount of nutrients entering the lake. Forty years later, while still not totally free of pollutants and nutrients, Lake Erie is again a biologically thriving lake.
The experiment was performed October 17-26th, 2005. Four 100 ml graduated cylinders were filled with 90 ml of water from the Tennessee River. Each cylinder was labeled control, nitrate, phosphate, and nitrate and phosphate. Nothing was added to the control cylinder. The nitrate cylinder was added with 15 drops of nitrate solution. The phosphate cylinder added 15 drops of phosphate solution. And the nitrate and phosphate cylinder added 15 drops of nitrate solution and 15 drops of phosphate. Each cylinder was put under a grow lamp with a piece of paper covering it. Each cylinder was observed on Day 1, Day 3, and Day 7. The observation included the color, odor, and the dissolved oxygen. A member of each group went back to the lab to get the results for that day. An average was taken of the numbers and they were graphed.