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

Aeration is a process used in aquatic environments to increase the distribution of oxygen throughout the water. This technique can indeed help control the growth of algae, which thrive in environments with excess nutrients and low oxygen levels. By increasing oxygen levels, aeration can inhibit the growth of algae, making it an effective method for dealing with algal blooms.

On the other hand, macrophytes, which are larger aquatic plants, are not significantly affected by aeration in the same way that algae are. The growth of macrophytes is influenced by other factors such as light availability, nutrient levels, and water depth rather than simply by oxygen concentration in the water. Therefore, the correct association is that aeration may control algae but does not affect macrophytes.