How does water turbidity affect the depth that light reaches in a lake?

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lake Lake Ann in North Cascades National Park, Washington, U.S., viewed from the park's Maple Loop Trail. The North Cascades National Park is a large wilderness area that preserves majestic mountain scenery, snowfields, glaciers, and other unique natural features.

Water turbidity refers to the cloudiness of water caused by suspended particles, such as silt, organic matter, or phytoplankton. These particulates significantly impact the optical properties of a body of water by increasing its opacity and scattering incoming light.1

As light enters the water, it is subject to attenuation—a process where light intensity decreases with depth due to absorption and scattering. In turbid water, suspended particles deflect light rays into random directions, preventing them from penetrating deeply. Consequently, higher turbidity levels accelerate the rate at which light is lost, drastically reducing the depth to which sunlight can reach. This reduction in light penetration directly limits the energy available for photosynthesis at deeper levels. Scientists often measure these changes in turbidity and light attenuation using tools like a Secchi disk or specialized photocells to determine how particulate distribution affects light availability.1