What is often a major consequence of pesticide runoff into aquatic systems?

Pesticide runoff into aquatic systems can lead to significant environmental consequences, one of the most critical being the reduction of biodiversity. When pesticides enter water bodies, they can be toxic to a wide range of aquatic organisms, including fish, amphibians, invertebrates, and plants. This toxicity can cause direct mortality or sublethal effects that impair growth, reproduction, and behavior, ultimately leading to declining populations of sensitive species.

Additionally, the chemicals in pesticides can disrupt the balance of aquatic ecosystems. For instance, some pesticides might favor certain species over others, leading to a decline in species diversity as some organisms are eliminated or severely impacted. The loss of biodiversity can make ecosystems less resilient and more vulnerable to other stressors, such as climate change or habitat degradation. This cascade effect can severely disrupt food webs and ecological interactions, further threatening the stability and health of aquatic environments.

In contrast, the other options do not accurately reflect the typical outcomes of pesticide runoff. An increase in fish populations would not occur in polluted environments, and decreased water temperature or improved clarity also do not characterize the effects of pesticide contamination. Instead, pesticide runoff typically degrades water quality, contributing to harmful algal blooms or other water clarity issues, complicating the broader impacts on the ecosystem