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Harmful algal blooms, have been making the headlines a lot these days. But what exactly are they? As defined by the National Oceanic and Atmospheric Administration, “Harmful algal blooms, or HABs, occur when colonies of algae – simple plants that live in the sea and freshwater – grow out of control and produce toxic or harmful effects on people, fish, shellfish, marine mammals and birds.”  

Also, known as red tides, blue-green algae or cyanobacteria, these blooms can be found in all 50 states and are a major environmental problem having a severe impact on human health, aquatic ecosystems and the economy.

Before we get into the details of what sets these blooms off and how you can prevent them, let’s try and get something straight. The terms “blue-green algae” and “cyanobacteria” get used interchangeably and this can cause some confusion. Which one is it, an algae or a bacteria? Cyanobacteria are actually in the bacterial phylum but have characteristics common to algae. They obtain their energy through photosynthesis and are the only photosynthetic single-celled organism able to produce oxygen. Most cyanobacteria produce a blue accessory pigment called phycocyanin giving the cells a bluish color when in high concentration, hence the more common term, blue-green algae. Because of the confusion that these two terms cause, the blue-green algae name is being eliminated from literature to avoid conflict. 

HABs generally occur when temperatures are warmest (late summer into early fall) and during extended periods of dry weather with low wind levels. Some HABs look like spilled paint or pea soup. Some look foamy, streaky or like wool. They can range in color as well. Anywhere from green, blue-green, brown, black, white, purple, and red. Algal blooms are naturally occurring and, when not excessive, are beneficial to lake and pond ecosystems. As stated above, it’s when they grow out of control and produce toxins that these blooms are considered a problem. The only way to determine if an algal bloom is actually an HAB is to have a professional look at it under a microscope. And to make things more confusing, scientists are unable to explain when or why these algal species release their toxins. Is it purely due to weather conditions or is it a defense mechanism? No one can really say one way or the other yet.

One thing we do know is that a major contributor to HABs is phosphorus. Phosphorus can come from livestock waste runoff, fertilizers and eroding soils. Heavy rain storms transport sediment carrying phosphorus to lakes and ponds thereby feeding potential HABs. Limiting the amount of sediments that enter your waterbody is one way to help prevent the potential occurrence of a HAB. This can be done by not directing any storm water runoff directly into your lake or pond and making sure there is a good, established vegetative buffer around your waterbody to intercept sediment and nutrients.

It is important to stay out of the water if there is a possibility of HABs and not to let children or pets play in HAB debris on shore. According to a factsheet provided by the Pennsylvania Sea Grant, some signs of HAB poisoning in humans are rashes, blisters and hives, and eye and nose irritation. If swallowed, abdominal pain, diarrhea, vomiting, numbness in lips, tingling in fingers and toes, dizziness, and headaches may occur. Signs that your pets, livestock or other wildlife have been poisoned by water containing HAB toxins are staggering, difficulty breathing, convulsions, salivation, weakness and vomiting. See a doctor if you or your children might be ill from HAB toxin and contact your veterinarian for sick pets.  

More information on HABs can be found at the following websites: www.epa.gov, www.noaa.gov and www.paseagrant.org.


The Bradford County Conservation District is committed to helping people manage resources wisely.  You can visit the Bradford County Conservation District at 200 Lake Rd in Wysox across from the Wysox Fire Hall. Contact us at (570) 485-3144 or visit our web page at www.bccdpa.com.