The use of oxygen by microbial decomposers will also continue to increase. This positive feedback process is referred to as eutrophication . Another indicator of agricultural pollution is the presence of the microbe fecal coliform . 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.