Harmful Algal Blooms

Harmful Algal Blooms, Cyanobacteria, and Cyanotoxins

June welcomes warm temperatures, summer fun and harmful algal blooms (HABs). HABs are formed by cyanobacteria, also known as blue-green algae but are actually photosynthetic bacteria. Their primary season runs from June to September, although they can survive all winter in reduced capacity, returning to thrive in warmer temperatures. Cyanobacteria occur in fresh, brackish and marine waters and thrive in nutrient rich warm waters. When cyanobacteria concentrate, they increase to form HABs at which point they cause aesthetic color issues and may produce taste and odor compounds such as geosmin and methyl isoborneol (MIB) and dangerous cyanotoxins.

 

Health Concerns

HABs are of concern for both recreational waters and drinking water supplies. It is well known that taste and odor compounds can cause significant problems for drinking water suppliers. Cyanotoxins pose another threat. There are numerous types of cyanobacteria producing numerous types of cyanotoxins. Cyanotoxins can cause stomach cramps, vomiting, diarrhea, fever, headaches, pains in muscles and joints, skin, eye and throat irritation, kidney dysfunction, liver damage and death. There are no federal drinking water standards for cynaotoxins, however, three cyanotoxins are on the Safe Drinking Water Act’s Contaminant Candidate List (CCL3) and Unregulated Contaminant Monitoring Rules including Anatoxin-a, Microcystin-LR and Cylindrospermopsin.

 

Testing and Monitoring

Taste and odor compounds may indicate the presence of cyanotoxins, however, this is not a reliable surrogate for measuring cyanotoxins. There are several methods available for measuring the concentrations of the various types of cyanotoxins, most of which need to be completed in a laboratory setting.Monitoring is a good method for staying ahead of cyanobacteria issues. The following are some steps that may be taken during a monitoring plan:

  1. Visual site inspection

  2. Monitoring total phosphorus

  3. Monitoring mass development of cyanobacteria

  4. Monitoring toxin content of cyanobacteria

 

Mitigation

Watershed management is the most effective measure for limiting growth of cyanobacteria. However, if cyanobacteria are already present, they can be removed through treatment. Algaecides should be used with extreme caution since they may exacerbate cyanotoxin levels. For more information on successful treatment methods, refer to CEI’s report entitled “Cyanobacteria: Initial Assessment of New England Water Supplies” completed in 2011 in association with the University of New Hampshire, Center for Freshwater Biology. The multiple-barrier approach is needed to effectively remove cyanobacteria and their harmful cyanotoxins. 

 

CEI's Report on Cyanobacteria, Initial Assessment of New England Water Supplies

 

For more information on harmful Algal Blooms Cyanobacteria and Cyanotoxins, please contact: Kristen Berger, P.E. Project Manager at 800-725-2550 x399 or [email protected].