California Wastewater Treatment Operator Practice Exam

When would you expect reduced algae population and less oxygen released into a pond?

1. Spring and summer

2. Fall and winter

3. During heavy rainfall

4. During drought conditions

The correct answer is: Fall and winter

The correct context for expecting a reduced algae population and less oxygen released into a pond is during fall and winter. During these seasons, temperatures drop, which typically slows down biological activity, including photosynthesis conducted by algae. The cooler weather can lead to a decrease in overall growth rates not only for algae but also for other aquatic plants. As photosynthesis decreases, the amount of oxygen produced by algae diminishes as well, leading to lower dissolved oxygen levels in the water. In contrast, spring and summer promote higher temperatures and increased sunlight, both of which can lead to rapid algal growth and higher oxygen release. Heavy rainfall can also affect nutrient levels in a pond, potentially leading to algal blooms due to increased nutrient runoff, while drought conditions may concentrate nutrients and disturb the balance of aquatic life, but still do not typically lead to longer-term reductions in algae populations or oxygen production as seen in colder months.