Which of the following elements is most likely to limit primary production in freshwater lakes?

• A. Oxygen
• B. Phosphorus
• C. Carbon
• D. Nitrogen

Answer: (B)

Verified step by step guidance

1. Understand the concept of primary production: Primary production refers to the synthesis of organic compounds from atmospheric or aquatic carbon dioxide, primarily through the process of photosynthesis, which is carried out by plants, algae, and certain bacteria.
2. Identify the role of nutrients in primary production: Nutrients such as nitrogen, phosphorus, and carbon are essential for the growth of these photosynthetic organisms. These nutrients are often referred to as limiting factors because their availability can limit the rate of primary production.
3. Consider the typical limiting nutrients in freshwater ecosystems: In many freshwater ecosystems, phosphorus is often the limiting nutrient. This means that the availability of phosphorus is the primary factor that limits the growth of algae and aquatic plants.
4. Evaluate the options given: Oxygen is not typically a limiting nutrient for primary production, as it is a byproduct of photosynthesis. Carbon is abundant in the form of carbon dioxide in the atmosphere and water. Nitrogen can be a limiting nutrient, but in freshwater lakes, phosphorus is more commonly the limiting factor.
5. Conclude that phosphorus is the most likely element to limit primary production in freshwater lakes, as it is often the nutrient in shortest supply relative to the needs of aquatic organisms.