Which freshwater ecosystem is typically least productive in terms of net primary productivity per unit area?

• A. River floodplain wetland
• B. Eutrophic lake
• C. Freshwater marsh
• D. Oligotrophic lake

Answer: (D)

Verified step by step guidance

1. Understand the concept of net primary productivity (NPP), which is the rate at which plants and other photosynthetic organisms produce organic compounds in an ecosystem, minus the rate at which they use some of this energy for respiration.
2. Recognize that productivity in freshwater ecosystems varies based on nutrient availability, light penetration, and other environmental factors.
3. Identify that eutrophic lakes and freshwater marshes are typically nutrient-rich environments, leading to high NPP due to abundant plant and algal growth.
4. Know that river floodplain wetlands also tend to have moderate to high productivity because of nutrient inputs from flooding and diverse plant life.
5. Understand that oligotrophic lakes are nutrient-poor, often with clear water and low levels of primary producers, making them the least productive freshwater ecosystems in terms of net primary productivity per unit area.