What negative effect can pesticides in water have on the ecosystem?

Pesticides introduced into aquatic environments can significantly disrupt the ecosystem, with one of the negative effects being the potential to cause diseases in aquatic organisms. When pesticides contaminate water bodies, they can harm a variety of species, including fish, amphibians, and invertebrates. The toxicity of these chemicals can lead to weakened immune systems in these organisms, making them more susceptible to infections and diseases.

In addition, the presence of pesticides can lead to bioaccumulation, where harmful substances accumulate in the bodies of organisms, further leading to health problems and disease outbreaks. When these affected organisms are part of the food web, the impacts can ripple through the ecosystem, affecting predator species and potentially leading to declines in animal populations.

The other options do not accurately reflect the impacts of pesticides in water. For instance, while we might expect that pesticides could enhance fish growth or improve food chains, the reality is that their harmful effects detract from healthy ecosystem function instead. Pesticides generally disrupt ecological balance rather than purify water or promote growth, as they introduce toxic substances that are detrimental to aquatic life.