Question

chemical fertilizers used in farms may be washed into local water bodies, such as ponds and lakes. this often results in a rapid growth of algae, an algal bloom in the ponds and lakes. explain how an algal bloom affects the oxygen levels in a lake ecosystem.

Explanation:

During the day, algae in an algal - bloom photosynthesize and produce oxygen. However, at night, they respire and consume oxygen. When the algae die, decomposers break them down. Decomposition is an oxygen - consuming process. Overall, the large amount of decomposition after the algal bloom often leads to a significant decrease in oxygen levels in the lake ecosystem, which can harm fish and other aquatic organisms.

Answer:

Initially, during the day, oxygen levels may increase due to algal photosynthesis. But at night, algal respiration consumes oxygen. After the algae die, decomposition by bacteria and other decomposers is an oxygen - consuming process, leading to a net decrease in oxygen levels in the lake ecosystem, which can cause hypoxia and harm to aquatic life.