Phosphorus is a nutrient that accumulates in waterways from fertilizer run-off, detergent, and other sources. It is the major cause of algal blooms, some of which are toxic. A lake with a reading of 0 - 10 mcg/L of phosphorus will not support algal blooms. Between 10 - 20 mcg/L, there is a possibility of a bloom. Over 20, you're really screwed.

Calcium is required for all life. Zooplankton is a major food source for many inhabitants of the lake, and it requires a calcium level of 1.5 mg/L in order to survive.