Theory 10/Thresholds & Tipping/Lakes
Eutrophication Is a Switch
The claim
A lake switches to algal dominance above a phosphorus threshold rather than degrading gradually, and the switch is not reversed by returning to the same concentration.
01Mechanism
Nutrient loading crosses a stability boundary between clear and turbid states; internal loading from sediment maintains the turbid state after external loading falls.
02Prediction
Recovery should require lower phosphorus than the level that caused the switch.
03Refutation
Reversible, gradual response would remove the bistability.