The Algal Bloom Action Team created this FAQ document for educator use in the fall of 2020. Please feel free to direct audiences directly to this page, copy this language into state-based outreach materials, or use as a reference in educational programming.
Please Note: You cannot tell if an algal bloom is harmful or producing toxins just by looking at it. In general, keep out of the water if there are visible scums or the water appears bright green, blue-green, red, or pink. Keep your pets from drinking or playing in the water.
GENERAL INFORMATION
What is this green stuff?
What kind of algae is it?
Why are harmful algal blooms a problem?
What types of algae are considered HABs?
What are cyanobacteria?
Are harmful algal blooms toxic?
Which toxins do harmful algal blooms produce?
What factors regulate harmful algal bloom growth?
Should I test my pond water for algal toxins?
What can I do to prevent harmful algal blooms?
IDENTIFYING, MONITORING, AND TREATING HARMFUL ALGAL BLOOMS
How can we identify algae?
Are occurrences of harmful algal blooms increasing?
How long should I expect this bloom to last?
Are there differences in how harmful algal blooms react in reservoirs versus lakes?
Are or can HABs be a problem in streams?
How long do the toxins persist?
What should we monitor to better predict harmful algal bloom outbreaks?
Should I treat an existing bloom?
How do I get rid of algae in my pond naturally?
Which chemicals are recommended?
Will using chemicals affect the other aquatic plants growing in my pond/lake?
What treatment methods besides chemicals can be used to treat algal blooms?
Do home remedies like vinegar, copper pennies, or baking soda kill pond algae?
Will chelated copper affect any other plants or organisms?
Are there any alternatives to copper available for use as algaecides?
Who do we call to treat it?
How much will treatment cost?
HUMAN HEALTH AND HARMFUL ALGAL BLOOMS
Can I safely swim in the greenish colored water?
What are the risk levels for direct contact (touching) with harmful algal blooms?
What are the risk levels for ingesting (drinking) water contaminated with harmful algal blooms?
What should we do if a person has been exposed?
ANIMAL HEALTH AND HARMFUL ALGAL BLOOMS
What should we do if an animal has been exposed?
How can we prevent harmful algal blooms from contaminating our pet’s/livestock’s water source?
How long do pets/livestock need to avoid waters recently exhibited a bloom?
LANDSCAPE NUTRIENT MANAGEMENT PRACTICES AND HARMFUL ALGAL BLOOMS
How can we eliminate the problem?
OTHER RESOURCES
Where can I find more resources on harmful algal blooms?
******************************************************************************************
What is this green stuff?
Algae are terrestrial and aquatic organisms that produce energy through photosynthesis. They are a primary food source for other organisms and produce oxygen during their photosynthetic process. Rapid growth of algae, called algal blooms, occurs naturally across aquatic landscapes. One group of bacteria, cyanobacteria, has similar photosynthetic characteristics and functions in aquatic systems.
What kind of algae is it?
While some harmful algal blooms will have a distinctive look, many can be difficult or impossible to differentiate from harmless algae with the naked eye.
Why are harmful algal blooms a problem?
Recreation, land value, drinking water, and human/animal health can all be negatively affected by increased HABs. Their decomposition (and even nighttime respiration in smaller volumes of water like ponds) can result in a loss of oxygen from the water causing aquatic habitat shifts, aquatic species death, and a downturn for the tourism economy.
What types of algae are considered HABs?
Harmful algal blooms in the North Central Region of the United States are mainly caused by several types of cyanobacteria, commonly referred to as blue-green algae.
What are cyanobacteria?
Cyanobacteria, often referred to as blue-green algae, are common in nature and often increase drastically in late summer and early fall. Their excessive growth, often resulting in blooms, is encouraged by increases in nutrients (particularly phosphorus and nitrogen from soil and nutrient leaching from agricultural systems or municipal sewage wastes), warm water temperatures, sufficient light, and calm conditions. Many blooms, called harmful algal blooms (or HABs) are capable of producing dangerous toxins.
Are cyanobacteria toxic?
It depends. Not all cyanobacteria produce toxins, but if and when they do, the toxins can cause mild to serious health issues to humans and animals. The neuro and liver toxins that are produced by cyanobacteria can produce symptoms of poisoning within 20 minutes of ingestion. These symptoms include weakness, staggering, difficulty in breathing, convulsions, and in some cases, death.
Which toxins do harmful algal blooms produce?
There are over 80 known cyanotoxins produced by HABs; three of the more prominent ones are microcystin, cylindrospermopsin, and anatoxin-a. Microcystins, which are hepatotoxins (liver toxins), are likely the most prevalent cyanotoxins in the environment. These cyanotoxins are produced by multiple cyanobacteria, including some of the more common species in freshwater systems such as Microcystis, Planktothrix, Oscillatoria, Dolichospermum (also known as Anabaena), and Aphanizomenon. Saxitoxin, a neurotoxin, can be produced by both cyanobacteria and some algal species. This toxin is mainly associated with red tides and shellfish poisoning in marine systems.
What factors regulate harmful algal bloom growth?
There are many factors that affect the growth and bloom of harmful algae in lakes and other waterbodies. Main factors relate to weather (especially temperature, sunlight, and wind-induced turbulence), upstream watershed management (including nutrient and sediment loads), and water conditions (available nutrients, the ratio of nitrogen to phosphorus, pH, dissolved oxygen, and turbidity). Blooms happen when the right combination of factors are met. HABs are usually most prominent in late summer and early fall.
Should I test my pond water for toxic algae?
Positively identifying HABs is a specialized skill, even among water professionals. A microscope is essential. If you don’t have relevant training, familiarize yourself with local professionals who do. Further, even if HABs are identified, you can’t visually detect if they are producing toxins.
What can I do to prevent harmful algal blooms?
Know which labs, universities, or state agencies can help in identifying whether an algal bloom is actually a HAB. The actions of an individual can have watershed-level impacts locally and downstream. Individuals should be encouraged to think holistically when considering actions on their property. Decrease phosphorus and nitrogen use near water bodies as HABs need these nutrients to grow. Don’t feed waterfowl, such as ducks and geese, as their excrement may increase nutrient input into the water body. Talk with your neighbors about best management practices for reducing HABs. Encourage forums that involve researchers, agency personnel, practitioners, farmers, and riparian and other landowners to discuss how HABs can be managed or prevented. Hold programs to teach people about HABs and human health issues. Participate in discussions, workshops, and seminars to learn about the latest research and activities to reduce and manage HABs. Lead by example through signage, statements, and testimonials to peers and the public regarding efforts to mitigate nutrient losses and HABs and health-related concerns. Farmers, golf course managers, and homeowners should focus on the efficiency of nitrogen and phosphorus use and apply fertilizer using the right source, timing, rate, and placement. Identifying and reporting the presence of HABs help determine their patterns of occurrence and can help alert the public when a concern arises. To help in this effort, the Centers for Disease Control and Prevention has launched the One Health Harmful Algal Bloom System (OHHABS), a voluntary reporting system available to all state and territorial health departments to help track HAB occurrence.
How can we identify algae?
While some harmful algal blooms will have a distinctive look, many can be difficult or impossible to differentiate from harmless algae with the naked eye. A fluorometer or optical probe that can detect the pigment phycocyanin is a useful tool in determining the presence of a bloom (although not in identifying the responsible organism). Identify local literature regarding “jar” and “stick” tests. Microscopic colonies of planktonic blue-green algae cannot be lifted from the water on a stick; long, filamentous colonies of green algae can. Common planktonic blue-green algae (HABs) will often float to the surface of a jar of water; planktonic green algae and diatoms will settle to the bottom
Are occurrences of harmful algal blooms increasing?
HABs are increasing in frequency worldwide. Occurrences and severity of harmful algal blooms may increase with warmer temperatures and increased phosphorus runoff from land application of fertilizers and animal waste, soil runoff, and municipal sources.
How long should I expect this bloom to last?
Under continuing favorable conditions, blooms may last for several weeks. Some cyanobacteria can survive under ice and throughout winter conditions. However, blooms usually do not persist; rain, heavy winds or cooler temperatures may inhibit or break up blooms.
Are there differences in how harmful algal blooms react in reservoirs versus lakes?
When researchers refer to HABs in their research related to bodies of water, they often use reservoirs and lakes interchangeably.
Are or can HABs be a problem in streams?
HABs can be a problem in any body of water, including streams and large rivers. Researchers are working to understand HABs in diverse waters.
How long do the toxins persist?
It depends largely upon microbial activity that breaks down toxins and exposure to sunlight.
What should we monitor to better predict harmful algal bloom outbreaks?
Continuous records of HAB-driving factors (weather, watershed management) and available statistical models can be used for HAB prediction. Occasional water sampling during long drought periods and increased agricultural activity in a watershed can be used for early detection of growth of cyanobacteria. If HABs have been seen in the past in the lake, a simple monitoring of weather conditions (air temperature and precipitation) near the lake (e.g., www.cocorahs.org, a community-led weather station network) and watershed management (crop planting and harvesting, fertilizer application, barren soil) can be used to increase awareness of potential blooms.
Should I treat an existing bloom?
Successful treatment will end the production of any new toxins, but the dying cells can release toxins back into the water. Thus, be cautious about using the water after treatment.
How do I get rid of algae in my pond naturally?
Just like land plants, all algae need an adequate supply of nutrients, particularly phosphorus and nitrogen, for growth. By reducing nutrient runoff into your pond, you will slow their overall growth. This process will likely not occur within the season or perhaps for several seasons. But, eventually, growth will be reduced. Keeping water circulating in the pond (e.g., using diffuser aeration) may also help to slow algal growth, but larger plants may then dominate in the pond.
Which chemicals are recommended?
Although they can be tenacious, blue-green algae respond to commonly used algaecides or chemical flocculants that remove nutrients and suspended particles from the water column. Benthic HABs, or those growing at the bottom of the lake, are even more tenacious and may require the application of different algaecides in series or combining an algaecide, herbicide, and surfactant. Water supplies impacted by HABs should be treated or left unused until tested safe and the bloom has disappeared.
Will using chemicals affect the other aquatic plants growing in my pond/lake?
Possibly. Chemical applications are associated with some environmental risks and should only be trusted to trained and licensed professionals in public or common waters. Be certain to adhere to label guidelines if you choose to apply a chemical algaecide to your own private waters.
What treatment methods besides chemicals can be used to treat algal blooms?
In addition to nutrients, algae need sunlight to photosynthesize and grow. Any method that blocks sunlight may deter algal growth. This includes long term solutions such as planting trees that provide shade over the water; or shorter term methods such as planting native aquatic plants that will compete with algae. Non-toxic dyes that color the water and decrease algal photosynthesis may be used in some situations, but research on their effectiveness is limiting. If they are used, these nontoxic dyes should be used mainly in calm, non-flowing waters with no inlet or outlet.
Do home remedies like vinegar, copper pennies, or baking soda kill pond algae?
Home remedies should be avoided. Pesticides and herbicides undergo a rigorous approval process and are labeled to detail safe applications. It is illegal to apply household chemicals without such labels as a pesticide or herbicide; if applied in concentrations high enough to have an effect, there will likely be detrimental side effects to non-target organisms.
Will chelated copper affect any other plants or organisms?
Chelated copper is a blend of two compounds which allows copper to break down and stay in solution for a longer period of time than copper sulfate. Both interfere with enzyme production in the algae. Both of these copper products can be toxic to some submerged plant species, a few species of fish, particularly rainbow trout, and also to zooplankton, tiny crustaceans that eat algae. The toxicity depends on the bicarbonate hardness (alkalinity) of the water, with toxicity decreasing as alkalinity increases. Be certain to adhere to all label guidelines when applying any algaecide.
Are there any alternatives to copper available for use as algaecides?
Sodium carbonate peroxyhydrate, a combination of sodium carbonate and hydrogen peroxide (and also known as sodium percarbonate) can be effective at suppressing some floating algal blooms and has fewer potential unintended residual effects than copper. It can also be applied to benthic blooms (those that attach to a pond’s bottom) to enhance a follow-up application of copper. The herbicides endothall and flumioxazin are also effective on some algae, but tend to be more expensive than products labeled as algaecides. They also may be damaging to some of the larger aquatic plants. Be certain to adhere to all label guidelines when applying any algaecide.
Who do we call to treat it?
Many local pond-management contractors and others licensed to apply pesticides to aquatic habitats will be able treat harmful algal blooms. Further, all states in the North Central Region have state agencies that provide information on permits and regulations concerning the treatment of HABs. If you feel unsure about the quality of the water, you can visit or consult with your state’s HABs monitoring program staff: https://www.epa.gov/cyanohabs/state-habs-monitoring-programs-and-resources
How much will treatment cost?
Treatment costs vary widely. In the long run, putting effort into prevention rather than treatment may save money.
Can I safely swim in the greenish colored water?
Keep out of the water if there are visible scums, or the water appears bright green, blue-green, red, or pink. Also, keep your pets from drinking or playing in the water. Look for any signage that may be posted on public water by management agencies.
What are the risk levels for direct contact (touching) with harmful algal blooms?
Contact with skin toxins (dermatoxins) can cause rashes and skin irritation.
What are the risk levels for ingesting (drinking) water contaminated with harmful algal blooms?
Drinking contaminated water from stagnant ponds or other water-containing structures, like lagoons, can cause sudden death in animals including livestock and pets. These symptoms include weakness, staggering, difficulty in breathing, convulsions, and death.
What should we do if a person has been exposed?
If you were exposed to HABs and are now experiencing symptoms, immediately contact a poison control center or your doctor. Report suspected HAB-toxin symptoms to your state or local department of health.
What should we do if an animal has been exposed?
If you suspect an animal has suffered poisoning from a bloom, immediately contact a veterinarian. If death is caused by a bloom, report it to responsible monitoring agencies. Report suspected HAB-toxin symptoms to your state or local department of health. Report impacted water bodies to responsible monitoring agencies and inform other pet owners and livestock users through community groups or public signage.
How can we prevent harmful algal blooms from contaminating our pet’s/livestock’s water source?
Several prevention steps can be taken to help limit HABs in water sources. Preventing nutrient runoff and circulating stagnant waters are two examples.
How long do pets/livestock need to avoid waters that recently exhibited a bloom?
It depends on whether or not the bloom is from cyanobacteria (also called blue-green algae) or true algae (like green algae or diatoms). The majority of algal blooms caused by true algae are not harmful to pets. But, if the bloom is due to harmful algae or cyanobacteria, even after it disappears, some toxins may be present as they are released from the dying algal cells. It’s difficult to pinpoint a time when the water is again safe for pets. Some contractors are able to test for toxins, but repeat tests or tests for multiple compounds can become expensive. Watch your pet for signs of vomiting, diarrhea, or difficulty in breathing if they drank water from the pond.
How can we eliminate the problem?
Nutrient management practices that provide cost savings to individuals should be emphasized. Private sector partners like certified crop advisers are the front-line messengers who can provide nutrient management information to farmers and landowners. Collaborations with crop advisers are an effective method for sharing information about nutrient management for managing HABs. Watershed associations, coalitions, or management authorities can encourage citizens living in the watershed to adopt management practices that help reduce nutrient runoff. A TMDL (total maximum daily load) can be used to measure progress and establish targets for citizens to achieve. Erosion control and soil quality restoration on both urban and rural landscapes are the best defenses against excessive phosphorus loss. These long-term nutrient management strategies will provide additional benefits to the landowner as well as help retain valuable topsoil. Encourage legislators to develop science-based standards for HAB toxins in recreational and drinking water. Collaborate with lake associations and water citizen groups to post signage about HABs, particularly if they are not well-publicized by state or local agencies. Establish HAB monitoring, reporting, and forecasting programs to help identify where blooms are occurring. A simple monitoring of weather conditions (air temperature and precipitation) near the lake (or at www.cocorahs.org community-led weather station network) and watershed management (crop planting and harvesting, fertilizer application, barren soil) can be used to increase awareness of potential blooms. Farmers and landowners are encouraged to assess their property for nitrogen and phosphorus loss risk potential, and test tile drainage to determine any contribution to nutrient loading downstream. Findings from field and farm assessments and monitoring should be addressed through water quality management strategies and conservation practice implementation. Encourage researchers to seek research opportunities to further knowledge on predicting and controlling HABs, and determining the environmental drivers of HABs and toxin production. Sharing methods and protocols with other professionals for HABs education and response is also encouraged.
Where can I find more resources on harmful algal blooms?
State environmental agencies, University Extension offices, local conservation districts, NRCS, and EPA, as well as farm organizations, private sector companies, and research institutions can provide technical assistance, support, problem troubleshooting, and serve as an informational forum to support practice implementation. State and federal cost-share programs may be available to assist with implementing nutrient management practices. For private waters, there may be contractors in your area that provide identification services. Some public agencies maintain lists of these private entities. Know the relevant contact to report suspected blooms. After reporting a suspected bloom, your state’s department of health may request reports of related illness. The CyAN app is a new collaborative effort by several federal agencies and is publicly available (at present only) to Android devices. It applies an algorithm to flag satellite images for surface blue-green blooms on a map interface that includes more than 2,000 of the United States’ larger lakes and reservoirs.