Which of the following is NOT a problem caused by aquatic weeds?

The correct choice indicates a factor that does not result from the presence of aquatic weeds. Aquatic weeds can significantly alter habitats by dominating water bodies, which affects the ecological balance. They can also impede water flow, causing issues for navigational and hydraulic systems. Additionally, aquatic weeds can lead to bad tastes and odors in water due to decay and the release of certain compounds.

In contrast, increased oxygen levels are typically associated with healthy aquatic environments and are improved through photosynthesis by aquatic plants. However, many invasive or overabundant aquatic weeds can lead to oxygen depletion when they die off and decompose, thus making the increase in oxygen levels from these weeds an unlikely effect. Therefore, the assertion that increased oxygen levels are caused by aquatic weeds is not accurate in this context.