Which of the following is a typical indicator of water quality?

Levels of coliforms serve as a key indicator of water quality because they reflect the potential presence of harmful pathogens. Coliform bacteria are commonly found in the environment, particularly in soil and the feces of warm-blooded animals. Their presence in water suggests possible contamination by fecal matter, which can carry disease-causing microorganisms. Thus, testing for coliform levels is a standard method used by water quality professionals to evaluate the safety of drinking water and indicate the effectiveness of water treatment processes.

While color variation, temperature fluctuations, and the presence of algae can provide some information about water quality, they are not as direct an indicator of potential health risks as coliform levels. Color changes can result from natural organic matter or sediments and do not necessarily indicate contamination. Temperature can influence water chemistry and biological activity but does not directly measure the safety or quality of the water itself. The presence of algae may indicate nutrient loading but does not inherently imply that the water is unsafe for drinking. Therefore, coliform levels are a more reliable and direct indicator of water quality.