What are harmful algal blooms?
Freshwater harmful algal blooms (HABs) are significant and excessive growths of blue-green algae, also known as cyanobacteria. All freshwater lakes inhabit native blue-green algae species that are capable of producing HABs. Several of these species can at times produce toxins (called cyanotoxins) that are harmful to the nervous system (neurotoxins), the liver (hepatotoxins), and the skin (dermatoxins) of humans and other animals. In addition to cyanotoxins, HABs are can be harmful to the lake ecosystem, causing depletion of oxygen levels which can create fish kills.
What causes HABs to form?
General contributing factors that promote the formation of HABs are:
- Ample/excessive sunlight - Low-water or low-flow conditions
- Warm temperatures - Excessive nutrients (nitrogen & phosphorus)
Although some HABs occur during the cold seasons, they more frequently occur during the summer, when temperatures are high, sunlight is ample, and the flow of incoming water is low. Also, one of the most influential factors of HAB growth is the concentration of nutrients such as nitrogen and phosphorus. Nitrogen and phosphorus are both required by blue-green algae to live and are often scarce in the environment, therefore limiting growth. Most nitrogen and phosphorus pollution (also known as nutrient overloading) comes from the runoff of agricultural fertilizer, lawn fertilizer, untreated human sewage (storm overflows), and untreated animal sewage from concentrated animal feeding operations.
Additional HAB Information
For more information about HABs in the Louisville District, including information about state-coordinated HAB response plans or to request HAB data, please call 502-315-3217 or email the Louisville District Water Quality Team at firstname.lastname@example.org.
NOTICE: All data contained herein is preliminary in nature and therefore subject to change. The data is for general information purposes ONLY and SHALL NOT be used in technical applications such as, but not limited to, studies or designs. All critical data should be obtained from and verified by the United States Army Corps of Engineers, Louisville District, Water Quality Team, 600 Dr. Martin Luther King Jr. Place, Louisville, KY 40202. The United States of America assumes no liability for the completeness or accuracy of the data contained herein and any use of such data inconsistent with this disclaimer shall be solely at the risk of the user.