What type of biological contaminant might affect water quality?

Zebra mussels are a type of biological contaminant that can significantly impact water quality. As an invasive species, they can proliferate rapidly in aquatic environments, leading to adverse effects on local ecosystems. They filter large amounts of water for food, which may deplete phytoplankton populations and thus disrupt the food chain. Additionally, their presence can lead to increased maintenance costs for water treatment facilities due to clogging of pipes and filtration systems. This alteration of the aquatic environment can result in poorer water quality, affecting both human and ecological health.

In contrast, heavy metals, microplastics, and chlorine are not classified as biological contaminants. Heavy metals refer to inorganic pollutants that can leach into water sources from industrial processes or runoff. Microplastics are small plastic particles resulting from the breakdown of larger plastic items or from the use of certain products. Chlorine is commonly used in water treatment as a disinfectant to kill pathogens but is not itself a contaminant in the same way biological organisms like zebra mussels are. These distinctions clarify why zebra mussels are the correct answer in terms of biological contaminants affecting water quality.