Which of these ecosystems has the lowest net primary production per square meter?

Options

A. A coral reef
B. An open ocean
C. A grassland
D. A marshy area

Answer

To determine which ecosystem has the lowest net primary production per square meter, we need to understand what net primary production (NPP) is and the factors affecting it in various ecosystems.

### Step-by-Step Solution:

1. **Define Net Primary Production (NPP)**:
- NPP is the rate at which plants and other photosynthetic organisms produce organic compounds in an ecosystem. It is calculated as the difference between gross primary production (GPP) and the rate of respiration by the producers.

2. **Identify Factors Affecting NPP**:
- Different ecosystems have varying levels of resources such as light, water, and nutrients, which impact their NPP.
- For example:
- **Deserts**: Limited water availability leads to low NPP.
- **Tundra**: Cold temperatures restrict plant growth, resulting in low NPP.
- **Open Oceans**: Generally low nutrient availability can limit NPP despite large areas.
- **Lakes and Streams**: Nutrient availability can also be low, affecting NPP.

3. **Compare Ecosystems**:
- Among the ecosystems mentioned (desert, tundra, open ocean, lakes, and stream biomes), we need to determine which has the lowest NPP.
- Deserts and tundras are known for their low NPP due to extreme conditions.
- Open oceans, while vast, often have nutrient limitations that can also lead to low NPP.
- Lakes and streams can vary, but they often have higher nutrient levels than deserts and tundras.

4. **Conclusion**:
- Based on the information provided, the open ocean has the lowest net primary production per square meter compared to the other ecosystems listed. Therefore, the correct answer is **open ocean**.

### Final Answer:
The ecosystem with the lowest net primary production per square meter is the **open ocean**.

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