Turbidity & Clarity Experiment

Learning Intention: 

• Identify possible environmental and recreational complications that can be attributed to clarity and turbidity

Turbidity and clarity 

Water Clarity is affected by turbidity, which can block sunlight’s ability to pass through water. Lack of sunlight caused by too much turbidity in water can have a detrimental effect on aquatic life.

Clarity indicates how deep light can penetrate into the water, and can be measured with a Secchi disk at any site where the water is deep enough. Turbidity or cloudiness in water is caused by suspended solid matter, which limits sunlight’s ability to pass through water.

There are many possible sources of turbidity. Most people think primarily of sediment, stirred up from disturbed or eroded soil, as clouding the water. But microscopic plankton, such as algae, can also contribute to high turbidity when their numbers are overabundant, usually due to excess nutrients and sunlight.

Turbidity blocks out the light needed by submerged aquatic vegetation (SAV’s). Lack of SAV’s decreases the amount of oxygen in water and leaves the water with less ability to support aquatic life.

Turbidity also reduces visibility for fish that are sight breeders or egg layers, clogs gills of organisms not adapted to a certain level of turbidity, smothers benthic creatures and eliminates habitat spaces. Suspended sediment can carry excess nutrients and pesticides throughout the water system. Suspended particles near the water surface absorb additional heat from sunlight, raising surface water temperature. Apparent water color, microscopic examination and stream walk observations can help determine the sources of turbidity. Moderate levels of turbidity can indicate a healthy, well-functioning ecosystem in which plankton flourish at a reasonable level to form the foundation of the food web. High turbidity and low clarity is an indicator of either runoff from disturbed or eroded soil or blooms of microscopic organisms due to high nutrient inputs. Very clear water is not perfect either—open ocean and crystal clear tropical waters support only sparse plant and animal life.