High turbidity may be caused by; soil erosion, waste discharge, urban runoff, flooding, dredging operations, channelization, increased flow rates, algae growth, or even too many bottom-feeding fish (such as carp) that stir up bottom sediments. If water becomes too turbid, it loses the ability to support a wide variety of plants and other aquatic organisms.

Increased turbidity can affect a stream and the organisms that live in it in many ways. Suspended solids may cause the water color to change. Turbid waters usually become warmer as suspended solids which darken the water absorb heat from sunlight. Warm water holds less oxygen than cold water, so oxygen levels will decrease.

Suspended solids reduce the amount of light that can pass through the water. As less light penetrates the water, photosynthesis slows releasing less oxygen into the water. If light is blocked to bottom dwelling plants, they will cease to produce oxygen and will die. As they decompose, bacteria will use up even more oxygen from the water.

Suspended solids can clog fish gills, reduce their growth rates, decrease their resistance to disease, and prevent proper egg and larval development. As particles of silt, clay, and other organic materials settle to the bottom, they can suffocate newly hatched larvae. Settling sediments can fill in spaces between rocks which could have been used by aquatic organisms for homes.