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The Scoop on Fecal Coliform

Yellow spots are fecal coliform colonies grown in laboratory from water sampleFecal coliform is a group of bacteria which are present in large numbers in the intestines of warm blooded animals and humans. When these bacteria are in the natural environment, it is usually in the form of excrement, feces, or poop. One bacteria group you may have heard of, E. coli, is a type of fecal coliform. Because fecal coliform is present in all warm blooded animal and human feces, it is used to indicate fecal pollution. Feces may contain a whole variety of dangerous bacteria and viruses, so monitoring for its presence and quantity is critical for public health.

Knowing how much fecal coliform is present in coastal water is particularly important for managing shellfish harvesting because shellfish are filter feeders. Shellfish, such as clams, mussels and oysters, can filter tens to hundreds of gallons of water daily. If impurities and bacteria are present in the water, they will stay behind in the shellfish tissue and build up over time. As a result, bacteria can be 100 times more concentrated within the tissue than in the surrounding water.

List of fecal coliform sourcesAll warm blooded animal feces contains fecal coliform. This includes waste from farm animals such as horses, cows, sheep, pigs, and chickens. That’s why farms are encouraged to use Best Management Practices that prevent pollution associated with manure and other animal waste from running off into nearby water sources. Waste from domestic pet animals, such as dogs and cats also impacts water quality. Beaches where people frequently walk their dogs and do not pick up dog waste will likely show high fecal coliform counts. In addition to farm and domestic animals, fecal waste from wildlife may contribute to elevated fecal counts in coastal waters. Areas where large numbers of migratory birds gather as they pass through on seasonal migrations may have high fecal coliform counts that can lead to seasonal shellfish area closures.

People are another source of the fecal coliform pollution that threatens Maine’s shellfish resource. From wastewater treatment plant outfalls, poorly functioning septic systems, and outhouses to illegal marine discharge into the water, people have a large impact on water quality.

The DMR Public Health Division Shellfish Growing Area Classification Program regularly tests for fecal coliform in coastal water using a membrane filtration method for laboratory analysis. Water samples are collected in the field at numerous monitoring stations along the Maine coast and are then taken back to the lab for processing. Each water sample is poured through a filter with pore sizes fine enough to capture fecal coliform bacteria. Each filter paper is then placed on a food source (a semisolid substance called agar) and incubated. If bacteria are present on the filter they will grow into yellow colored colonies that can be seen by the naked eye. After 24 hours, the number of bacteria colonies that were present in the water sample are counted by DMR staff using a dissecting microscope. The results of these laboratory tests are compared to National Shellfish Sanitation Program established water quality standards. Cumulative results over time will determine if shellfish can be harvested and sold for human consumption in areas where samples are collected.

Learn more about the Shellfish Growing Area Program here.