For many Canadians, summer time means time at the lake, swimming, fishing, boating, and relaxing. Nothing can spoil this experience like blue-green mats of muck, caused by algal blooms. These blooms negatively affect not only recreational activities but also put drinking water source, property values, wildlife, and human health at risk. In the 1970s, scientists discovered that the nutrient phosphorus caused algal blooms, which led to new regulations and improved sewage treatment. Nevertheless, blooms continue to plague many Canadian lakes. To investigate what might be happening, scientists looked to see whether phosphorus might be recirculating from the mud at the bottom of lakes back into the water.