Which of the following is NOT an effect of aquatic weeds?

The assertion that improving water quality by filtering pollutants is not an effect of aquatic weeds is accurate. While some aquatic plants can provide benefits, such as oxygenation of water and habitat for aquatic life, excessive growth of aquatic weeds often leads to negative consequences. For instance, weed infestations can contribute to oxygen depletion, which is detrimental to fish populations.

Aquatic weeds generally compete with other organisms for nutrients and light, which can harm fish populations by stunting growth or creating conditions unfavorable for their survival. Furthermore, dense growth of weeds can hinder recreational activities like swimming and boating, making these waterways less accessible and enjoyable for users. Therefore, the presence of aquatic weeds usually leads to complications in aquatic ecosystems rather than improvements in water quality.