What type of weeds are exposed to freezing, drying, or heat during water level manipulation?

The correct answer is emergent weeds. These types of weeds are typically found at the water's edge and extend above the water level. When water levels are manipulated, such as through lowering the water body for resource management or control purposes, these emergent weeds can become exposed to harmful environmental conditions like freezing temperatures, drying air, or direct heat from sunlight. This exposure can lead to the death of the plants or significantly reduce their growth potential.

Submersed weeds are typically underwater and not directly exposed to the same environmental stressors during water level manipulation since they remain submerged even if the water level drops marginally. Floating weeds are those that float on the surface of the water and may not experience the same degree of exposure during such manipulations. Annual weeds, while they can be affected by changes in environmental conditions, are not specific to aquatic environments and their life cycle may not align with the definitions pertaining to the aquatic systems in question.