Having a large amount of suspended solids—fine particles floating in the water—can directly affect fish by damaging their gills, changing their behavior, lowering their resistance to disease, and blanketing spawning gravels. Suspended solids can make the water appear cloudy and thus affect aesthetic appreciation of the rivers and safety for swimmers. Suspended solids may be fine soil particles common in stormwater runoff, organic particles including bacteria and algae, or fine particles discharged with wastewater.