What is an example of mechanical control of aquatic weeds?

Mechanical control of aquatic weeds involves the physical removal or disruption of the plants. Underwater weed cutters exemplify this approach as they are specifically designed to cut and manage the growth of aquatic vegetation. This method physically removes the weeds from their source, thereby reducing their population and preventing them from outcompeting desirable species or impairing recreational activities.

In terms of the other options, natural predators (A) relate to biological control strategies, where organisms are introduced to manage pest populations. Water quality management (C) focuses on improving the environmental conditions to support healthy ecosystems but does not directly involve physical removal of weeds. Phytoremediation (D) is a process that utilizes plants to remove or stabilize contaminants from the environment, rather than specifically controlling weed growth through physical means. Thus, underwater weed cutters stand out as a clear example of mechanical control.