Dead zones–large areas of water with little oxygen–occur when excess fertilizer and untreated sewage seep into the waters. The dead zones are usually seasonal and they cause fish and other bottom-dwelling animals to move outside the area to avoid being suffocated. Much underwater life also dies. Since the 1960s the number of dead zones worldwide has doubled with each passing decade. In Lake Erie, a massive multiyear study is underway to study how the lake’s ecosystem is affected by its dead zone. Producer Mhari Saito has our report.