Primary productivity is controlled by several key environmental factors that can vary significantly.

• Light Availability: The total available light is of great importance. Studies in Alaskan oligotrophic lakes showed that average photosynthesis was nearly proportional to the available light energy.
• Nutrient Limitation: Following Liebig’s law of the minimum, the availability of certain nutrients often limits growth.
  • Different lakes are limited by different elements (e.g., magnesium, nitrogen, and phosphorus in Brooks Lake; potassium, sulfur, and molybdenum in Castle Lake).
  • The balance and interaction of the entire nutrient medium with the organism community is more critical than a single limiting factor.
• Spatial Variability: Productivity is not uniform within a single lake. It can be much higher near areas of nutrient inflow, such as streams draining disturbed watersheds, a phenomenon observed in Lake Tahoe.