Florida Wastewater Practice Test

What is one potential effect of excessive algal blooms in water bodies?

1. Improved water clarity

2. Decrease in dissolved oxygen levels

3. Reduced water temperature

4. Increase in fish populations

The correct answer is: Decrease in dissolved oxygen levels

Excessive algal blooms can lead to a significant decrease in dissolved oxygen levels in water bodies. This phenomenon occurs when the algae die off and decompose, a process that consumes a large amount of oxygen from the water. As oxygen levels drop, aquatic organisms, such as fish and invertebrates, can struggle to survive due to hypoxic (low oxygen) conditions. This can result in fish kills and a decline in overall aquatic ecosystem health. Understanding this effect emphasizes the importance of managing nutrient inputs to prevent algal blooms in the first place, as they disrupt not only water quality but also the integrity of aquatic habitats. In contrast, improved water clarity is unlikely because algal blooms typically create murky conditions. Similarly, the water temperature is not directly reduced due to blooms; instead, it may actually increase because the dense algae can absorb sunlight. Additionally, algal blooms do not promote an increase in fish populations; instead, they often cause a decline due to the resulting oxygen depletion and habitat degradation.