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Update on Cyanobacteria Bloom at Chris Greene Lake Last Summer

Last summer Parks and Recreation experienced a Harmful Algae Bloom (HAB) at Chris Greene Lake. This bloom resulted in higher levels of cyanobacteria being released in the lake, and we were instructed to restrict swimming, and close the water area at the dog park. We were under the guidance/direction of the Virginia Department of Health (VDH) and HAB task force for the duration of the event.

Cyanobacteria or blue - green algae are single-celled organisms that naturally exist in fresh or salt waters. They use sunlight to make their food. When there are many nutrients available in the water, the bacteria can grow rapidly or “bloom” to form a visible film or scum on the surface of the water. This is more likely to occur in warm spring and hot summer months, however, unseasonably warm temperatures in fall and winter can produce blooms. Cyanobacterial blooms are often green or blue-green in color although they can sometimes be red or brown.  They are common organisms found in lakes, rivers, and ponds (freshwater), as well as estuaries (brackish water).
We sought advice from the VDH “HAB” Task force and Solitude Lake Management, which is the industry leader in freshwater water quality management as to causes and possible solutions, and provided the following.
What causes blue-green algae blooms?
High quantities of nutrients in the water often lead to the formation of bacterial blooms. Nutrients may concentrate in natural bodies of water due to:
  • Inadequate water flow or exchange of water
  • Nutrients such as nitrogen and phosphorus from fertilizers used on farms and in urban and suburban yards, sewage, industrial waste, etc. being washed into waterways
  • Changes in rivers and their surroundings due to land clearing, farming practices, construction and housing
  • Higher than normal water temperatures  

Margaret Smigo with VDH, is on the HAB taskforce and has visited the site. She noted that we have a good riparian buffer in our watershed. Parks and Recreation does not use fertilizer in the parks so she surmises that the runoff from upstream is most likely the culprit of the high nutrient levels in the lake.

Solitude Lake management has provided us with two options that may reduce the risk of another event. A monitoring program that samples the lake twice per month that identifies type and levels of phytoplankton. If numbers of potentially harmful algae rise, they will recommend an early treatment to retard the bloom. Treatment would not pose any health issues and would not interrupt recreational activities.
Solitude Management has also proposed to place two, lake aeration compressors and 18 diffusers throughout the lake that will be used to oxygenate the water and aid in reducing lake water temperature.
Solitude Lake Management and VDH both have advised that while these measures are best practices in reducing the potential for an “HAB”, there is no guarantee that another “HAB” could occur.

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