Suspended and Attached Algae


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    Suspended and Attached Algae

    diatomsFree floating plants include large “true” plants like duck weed that float on the surface, and microscopic algae that live suspended in the water itself. These algae may exist as single cells, or in long filaments. 

    algaeIn lakes and ponds, most of these algae are suspended in the water. A green or brownish tinge to water may be the only evidence that algae are present, but under a microscope an amazing and diverse world is revealed. In moving water, microscopic algae are generally found attached to rocks or other substrate.

    Microscopic algae are the primary food for microscopic lake animals (zooplankton) and are an important food for many aquatic macroinvertebrates in rivers and streams.


    HABExcess nutrients in standing water (lakes, reservoirs) can result in “blooms” of algae that turn the water turbid. When the algae die, they sink to the bottom and decompose. In a stratified lake (during winter or summer), where the deep waters are not easily reoxygenated, this decomposition may suck all the dissolved oxygen out of the water. This can cause fish kills and odor problems.

    By late summer, these waterbodies with high concentrations of nutrients (nitrogen and phosphorus) may become dominated by cyanobacteria (often called blue green algae). These organisms often float in thick mats or form unsightly scums on the surface. They also may produce toxins. See Harmful Algal Blooms for more information.