Aeration may control which of the following, but does not affect which?

Aeration is a technique used in water management that introduces air into the water, increasing oxygen levels. This can lead to a number of ecological changes.

When it comes to algae, aeration can help control their growth by increasing the overall oxygen levels in the water, creating a more favorable environment for aerobic bacteria that compete with algae for nutrients. This means that while aeration can limit algae by promoting these beneficial bacteria, it does not drastically impact macrophytes (larger aquatic plants) in the same way. The increased oxygen can actually be beneficial to macrophytes, fostering their growth rather than controlling it.

Therefore, the option correctly suggests that aeration may control algae while having little to no effect on macrophytes, making it the right choice in the context of this question.