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Rise of the CyanoHABs

Cyanobacteria (also known as blue-green algae) are proliferating in the U.S. and worldwide, becoming a serious threat to freshwater resources and public health. Results from NCCOS harmful algal bloom programs are uncovering the secrets of why cyanobacteria are so successful so they can be used to develop new strategies to control them.

Cyanobacteria, which have evolved over 3.5 billion years, thrive in our modern world of warming temperatures and plentiful nutrients. Growing in freshwater, estuarine and marine ecosystems, they discolor and can cause foul odors and taste in drinking water and fish. Many produce a wide variety of toxins that can affect the liver, nervous system, digestive system and skin, and cause illness and death in humans, wildlife, and domestic animals exposed through contact, ingestion, or inhalation. Harmful cyanobacterial blooms are often termed “CyanoHABs.”

CyanoHABs thrive in warm, stratified waters and often use both inorganic and organic forms of phosphorus (P) and nitrogen (N). Some cyanobacteria can also use (“fix”) atmospheric nitrogen (N2), giving them an advantage where that nutrient is limiting growth, since most organisms cannot use N2.

Law- and policymakers usually focus on reducing P to control CyanoHABs. However, lakes and rivers today are increasingly inhabited by non-nitrogen fixing CyanoHABs and contain high concentrations of both P and N.

The studies suggest some tools available for short-term control are (1) increasing water mixing and flushing rates, which reduce the light or time available for CyanoHAB growth, and (2) decreasing nutrient inputs from sediments by dredging or capping with clay. However, in the long term, strict N and P management controls may be needed for the most successful reduction of CyanoHABs. Other options are also being investigated, such as flocculating CyanoHAB blooms with clay.

Learn more about CyanoHABs, why they are thriving, how they do it, and how best to control them from these NCCOS-supported research studies:

Learn more about our harmful algal bloom programs.

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