Another indicator of agricultural pollution is the presence of the microbe fecal coliform. Fecal coliform is a non-pathogenic bacteria that naturally occurs in the digestive tracks of warm-blooded animals. "Non-pathogenic" means fecal coliform does not cause diseases. However, it is often found in association with pathogenic (disease-causing) organisms.
Loose dirt, or sediments, from plowed fields is also a form of agricultural pollution. Like pesticides, fertilizers, and animal wastes, dirt from plowed fields can be carried by runoff to streams. Sediments cause increased suspended solids in streamwater. The suspended solids decrease light penetration through the water column. When the sediments finally settle to the bottom of the stream, they suffocate life there. This movement of loose dirt into streams is called siltation. The murkiness of the water is referred to as turbidity.
The problem of pesticides, fertilizers, animal wastes, and sediments in runoff can be increased by livestock grazing along the stream. Vegetation that grows near streams acts as a buffer. This vegetation absorbs toxins and nutrients and traps sediments before they reach the stream. Livestock remove the vegetation. Without a vegetation buffer, pollutants can move freely from a field into a stream. In addition, livestock increase erosion of banks along streams, and thereby increase the occurrence of siltation.
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