What effect do heavy metals like mercury have on water quality?

Heavy metals, such as mercury, can significantly impair water quality and pose serious health risks to both aquatic life and humans. When these metals enter water bodies, they tend to accumulate in the tissues of organisms, a process known as biomagnification. This means that as smaller organisms, which may also absorb these toxic substances, are consumed by larger predators, the concentration of heavy metals increases at each level of the food chain. The accumulation can lead to toxic effects including neurological damage, reproductive failure, and even death in various species. Moreover, these heavy metals can then enter the human food supply through the consumption of fish contaminated with mercury, posing health risks such as cognitive impairment and developmental issues in humans. Thus, the correct answer highlights the danger of heavy metals in the aquatic ecosystem and their potential to affect overall water quality and safety.