What is an indicator organism, and why is it used in water sampling?

An indicator organism is a type of microorganism that signals the presence of pathogenic organisms in water, particularly fecal contamination. The use of indicator organisms, like E. coli, is vital in water sampling because they are easier to detect and monitor than the pathogenic microorganisms themselves. E. coli specifically indicates contamination with fecal matter, which can carry harmful pathogens that pose health risks to humans and animals.

When water quality assessments are carried out, the presence of these indicator organisms provides a reliable proxy for potential microbial contamination. Since pathogens may not always be present in detectable numbers or may take longer to culture and identify, tracking indicator organisms is a practical approach for assessing water safety. This method allows for timely responses to contamination, helping to safeguard public health and ensure safe water supplies.

Other options do not accurately capture the role of indicator organisms in water sampling and do not address the primary function of identifying contamination risks associated with pathogens. This focus on the presence of specific microorganisms that indicate fecal contamination makes option C the correct choice.