♻️AP Environmental Science
3. Prairie pothole wetlands are freshwater marshes found across the Great Plains of North America, particularly in North Dakota, South Dakota, and parts of Canada. These wetlands are critical ecosystems that provide habitat for migratory waterfowl, filter pollutants from agricultural runoff, and sequester carbon. However, intensive livestock operations in the surrounding grasslands have led to nutrient pollution from animal waste, degrading water quality and disrupting ecosystem function. A conservation organization is working to restore a 50-hectare prairie pothole wetland that has been impacted by nearby concentrated animal feeding operations (CAFOs).
Parameter | Before Restoration (2020) | After Restoration (2024) | Target Level |
|---|---|---|---|
Nitrate-N (mg/L) | 12.5 | 4.2 | 5.0 |
Total Phosphorus (µg/L) | 450 | 180 | 150 |
Dissolved Oxygen (mg/L) | 3.2 | 7.8 | 6.0 |
pH | 8.9 | 7.4 | 7.0-8.0 |
Vegetation Type | Area (hectares) | Carbon Sequestration Rate (kg C/ha/yr) |
|---|---|---|
Emergent plants (cattails, bulrush) | 28 | 1,850 |
Submergent plants (pondweed) | 15 | 1,200 |
Floating plants (duckweed) | 7 | 980 |
Identify the terrestrial biome that is adjacent to prairie pothole wetlands in the Great Plains region of North America.
Describe one environmental problem, other than nutrient pollution, that concentrated animal feeding operations (CAFOs) can cause in adjacent aquatic ecosystems.
Explain how excessive nitrogen from animal waste can lead to decreased dissolved oxygen levels in the prairie pothole wetland.
Calculate the percent change in nitrate-N concentration between 2020 and 2024. Show your work. Based on the data in Table 1, the nitrate-N concentration in the wetland before restoration in 2020 was 12.5 mg/L. After restoration efforts in 2024, the nitrate-N concentration decreased to 4.2 mg/L.
Figure 1. Energy Flow in Prairie Pothole Wetland Food Web (per square meter per year; trophic-level biomass energy shown with 10% transfer between levels)
Calculate the total energy available to secondary consumers in the entire 50-hectare wetland per year, in kilocalories. Show your work. Based on Figure 1, the net primary productivity (NPP) of the prairie pothole wetland is 85,000 kcal/m²/yr. Energy is transferred through the food web from producers to primary consumers to secondary consumers to tertiary consumers. The wetland has a total area of 50 hectares. Note that 1 hectare = 10,000 m².
Propose a realistic solution that agricultural producers operating CAFOs could implement to reduce phosphorus loading into the prairie pothole wetland.
Calculate the total amount of carbon sequestered by all vegetation in the wetland per year, in kilograms. Show your work. Based on the data in Table 2, the restored wetland contains three types of vegetation. Emergent plants cover 28 hectares and sequester carbon at a rate of 1,850 kg C/ha/yr. Submergent plants cover 15 hectares and sequester carbon at a rate of 1,200 kg C/ha/yr. Floating plants cover 7 hectares and sequester carbon at a rate of 980 kg C/ha/yr.
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