With the rise of water temperature, dissolved oxygen:

Options

A. Remains unchanged when algal bloom occurs
B. Increases in amount
C. Decreases in amount
D. Is more available to aquatic organisms.

Answer

**Step-by-Step Solution:**

1. **Understanding Dissolved Oxygen (DO):**
- Dissolved oxygen refers to the amount of oxygen that is present in water, which is crucial for the survival of aquatic organisms.

2. **Effect of Temperature on Solubility:**
- The solubility of gases, including oxygen, in water is affected by temperature. As the temperature of water increases, the solubility of oxygen decreases.

3. **Analyzing the Question:**
- The question asks about the effect of rising water temperature on dissolved oxygen levels.

4. **Conclusion on Dissolved Oxygen Levels:**
- With an increase in water temperature, the dissolved oxygen levels decrease. This is because warmer water holds less oxygen compared to cooler water.

5. **Impact of Algal Blooms:**
- Algal blooms can further exacerbate the situation. When algal blooms die, they decompose, consuming even more oxygen in the process, leading to a further decrease in dissolved oxygen levels.

6. **Final Answer:**
- Therefore, the correct answer to the question is that dissolved oxygen decreases in amount with the rise of water temperature.