Water, like everything else on Earth, including you, is full of bacteria. Some bacteria are beneficial and some are not. Escherichia coli (E. coli) is a bacteria commonly found in the gastrointestinal tract and feces of warm-blooded animals. It is a member of the fecal coliform group of bacteria and is distinguished by its inability to break down easily. This bacteria is a preferred indicator for freshwater recreation and its presence provides direct evidence of fecal contamination from warm-blooded animals. It can easily be transported in runoff from sources in the watershed. Potential sources are wildlife, farm animals or poorly maintained septic systems. E. coli can get into the environment, and if contacted by people, can cause health problems and sickness. https://www.usgs.gov/
A simple water test for E. coli, "Easy Gel", is available form Microbiology Labs https://www.micrologylabs.com/ . Easygel uses a patented Coliscan media, which is a combination of color-producing chemicals and nutrients that mark coliforms, E. coli appears in differing colors for easy identification.
The LGA Lake Environment Committee (LEC) has been using Easy Gel to test Lake Gaston waters since 2017. The LEC purchases a number of these testing kits and makes them available to anyone who wish to test Lake Gaston water near their residence, swimming area, and or HOA common areas. Problem areas are identified and action taken to resolve issues. Results are compiled and provide useful data to demonstrate water quality.