How can urbanization negatively impact aquatic environments?

Urbanization can significantly impact aquatic environments primarily by increasing runoff and the amount of pollutants that enter waterways. As cities develop, natural landscapes are altered with the construction of impervious surfaces such as roads and buildings, which prevent water from being absorbed into the ground. This leads to increased surface runoff, where stormwater travels quickly over these hard surfaces, picking up a variety of contaminants such as oil, heavy metals, sediments, and nutrients before flowing into rivers, lakes, and oceans.

The surge in runoff not only introduces these pollutants into aquatic environments but also affects the physical and chemical properties of these water bodies. Elevated nutrient levels, for instance, can lead to algal blooms that deplete oxygen in the water, harming aquatic life and disrupting ecosystems. Additionally, the sedimentation from urban runoff can smother habitats that aquatic plants and animals rely on for survival.

In contrast, urbanization typically does not decrease water temperatures, improve biodiversity in wetlands, or enhance natural water filtration, as these options suggest. The alterations associated with urbanization generally lead to poorer water quality and degraded aquatic habitats.