Feature Article July 17, 2003
LAND O' LAKES NewsWeb HomeWhat's Magic About Lake Phosphorus?Phosphorus gets a lot of attention in discussions of lakes and water quality. Water quality analysis, results from the Lake Partners Program and 'lake capacity models' all emphasize phosphorus as the critical variable in lake water quality. Either by common sense or by remembering the 'law of the minimum', some privately wonder whether some of the other nutrients aren't important too.
Sure, they are. Nitrogen and even carbon are needed in large quantities by growing plants, the base of all food chains. However our focus on water quality is directed to things that we have some chance of controlling. Essentially that means something that we humans are responsible for and that we have the technical ability to control.
For example, nitrogen moves around the environment in many uncontrollable ways. It moves in the air in several chemical forms and, in several other forms, it is highly water-soluble and readily moves through the soil and waters. So, although nitrogen is common in human wastes, our technical ability fails to control its flowpaths in a lake's environment. Phosphorus does not move in air and several of its forms are poorly soluble in water so we can contain it better than nitrogen. We humans manage to put a lot of phosphorus into our wastes -- sewage, dishwasher and laundry wastes.
So if we monitor phosphorus in our lakes, the changes in its concentration in the water are relatable to our actions and are controllable by changing our actions. These are important if we want to measure something that will act as an 'indicator' of our effects on lake water quality. However, it does lead to a question that we should start thinking about. When we get really good at processing and containing our phosphorus wastes, and the phosphorus in our lakes no longer reflects our effects on the lake, what should then become our indicator? Predicting how much capacity a lake has for development will no longer work once we have disconnected our actions from the amount of phosphorus in the lake.
For now, phosphorus does have some magic in discussions of lake water quality and lake planning. Improving septic systems to keep it out of our lakes is important.
