Which of the following is most likely to limit primary production in fresh water lakes ?

The correct answer is Phosphorus.

Phosphorus is most likely to limit primary production in freshwater lakes.

Key Points

• Primary production is the process of conversion of light energy to chemical energy by green plants. For the aquatic ecosystem, usually, phytoplankton does this work.
• In an ecosystem, the primary production sets the balance of the energy budget.
• The amount of light and nutrients limits primary production.
• A limiting nutrient is an element that must be added for production to increase in a particular area.
• In this case, two important nutrients are Nitrogen and Phosphorus that limit primary production.
• Nitrogen act as an agent for algae blooms in the sea/ocean water.
• In the case of freshwater, the major source of pollutants is derived through domestic sewage and agricultural fields.
• Phosphate content present in soap, phosphate fertilizers, concentrated animal feeding operations, etc causes extra addition of phosphorus in the freshwater.
• It predominantly causes Eutrophication.
• Eutrophication means  is characterized by dense algal and plant growth in the water that causes threats to the survival of aquatic life  
• Phosphorus is the nutrient that limited cyanobacteria growth.