A few years of intensive artificial fertilization can have the same effect as thousands of years of natural fertilization. It can bring the concentration of phosphates to a critical level and to the point of no return. It must be mentioned, however, that aquatic plants are an essential and natural element of a healthy lake. It is only when the plants start reproducing excessively that it becomes a serious problem. This problem is also easily seen.
Every lake has microscopic algae in suspension in the water.
However, when excessive amounts of phosphates are present, the algae can reproduce at such a rate as to transform a clear lake into a real green pea soup. Rocks are often become covered with long filaments. A spurt of algae growth can be accompanied by sickening odors as well as troubled water. When the algae decomposes, it gives off phosphate that is used by other algae and the cycle goes on and on. The other symptoms are harder to recognize but they are nonetheless very serious.