Harmful Algal Blooms

What is a Harmful Algal Bloom (HAB)?

Microscopic algae are the base of the food web in aquatic systems, providing nutrients and oxygen for the higher trophic levels including benthic macroinvertebrates, fishes, and waterfowl. However, some of these algae are capable of producing toxins that can harm wildlife and/or humans. Algae blooms caused by species capable of producing toxins are called Harmful Algal Blooms or HABs.

Harmful Algal Blooms are a naturally occurring phenomena that can be found in nearly all aquatic environments, including lakes, ponds, rivers, and streams. Natural factors such as water temperature, pH, low water flows, light levels, and nutrient levels influence the growth and abundance of algae. Different algae species have different growth requirements and can bloom under different environmental conditions. Many species of algae tend of bloom in the summer but blooms can occur year round. Some species of algae can produce toxins under certain conditions, many of which are not yet fully understood.

In freshwater systems, HABs are typically caused by a type of algae called cyanobacteria, or blue-green algae. However, not all cyanobacteria species cause HABs. Some common blue-green algae species capable of cyanotoxin production include: Microsystis, Dolichospermum (formerly Anabaena), Aphanizomenon, Planktothrix, and Lyngbya. Additionally, the presence of these species does not confirm the presence of toxins. Only certain strains, in certain ecological and environmental conditions produce toxins.

Toxins produced by cyanobacteria are collectively referred to as cyanotoxins. These toxins can affect the liver, nervous system and/or the skin of people, pets, and wildlife. Children are more susceptible, than adults, to the effects of cyanotoxins. Cyanotoxins may be present before a visible bloom, during a bloom, or after a bloom. Cyanotoxins may persist in the environment for months or years after a bloom. Cyanotoxins and/or cyanobacteria blooms can float downstream affecting other areas. Harmful Algal Blooms are not restricted to lakes; they can form in rivers and streams as well. However, Harmful Algal Blooms tend to occur in calm, stratified waters.

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Micrographs of Common HAB-Capable Species
View micrographs of common HAB-capable species of cyanobacteria and species-specific bloom descriptions.

Quick Links

Reported HABs in WV
Updated August 23, 2023
Report a Bloom - Web Application
An interactive map which will allow you to report an algae bloom.
Report a Bloom - Form
Use this form to provide information about the potential blue-green algae bloom observed.
WV HAB Response Plan
The principal objective of DHHR’s HAB Response Plan is to provide a unified statewide approach to address HABs in West Virginia’s recreational waters and to protect people and animals from toxins produced by cyanobacteria.
Harmful Algal Bloom Story Map
A Closer Look into Harmful Algal Blooms and Toxins
HAB Advisory Maps
If there is a current HAB advisory, a map will be displayed.

What are the Effects of Cyanotoxins?

Cyanotoxins have a wide range of effects as hepatotoxins, neurotoxins, dermatoxins, and endotoxins. Symptoms vary depending on exposure route, duration, and toxin type/concentration.

Hepatotoxins damage the liver. Microcystin, Cylindrospermopsin, and Nodularin are hepatotoxins. Symptoms of exposure to hepatotoxins include abdominal pain, vomiting, diarrhea, liver inflammation, hemorrhaging, lesions, acute pneumonia, and death (within hours to days after exposure). Human cases are often reported from drinking water as well as ingestion of untreated/raw water, contact during recreational activities, and hemodialysis with toxin-laden water.

Neurotoxins are nerve toxins and include Anatoxin-a, Anatoxin-a(s), and Saxitoxins. Symptoms of exposure to neurotoxins include tingling, burning, numbness, drowsiness, staggering, incoherent speech, gasping, convulsions, and respiratory paralysis leading to death (within minutes to hours after exposure). Human deaths have been associated with shellfish consumption (saxitoxins). However, humans can be exposed to these toxins via recreational contact as well. Animal deaths, especially dogs, have been associated with recreational exposure. There is limited data available on neurotoxin exposure via drinking water.

Dermatoxins are skin toxins and include Lyngbyatoxin-a, Aplysiatoxin, and Lipopolysaccharides. Symptoms of exposure to dermatoxins are similar to swimmer’s itch and include skin rashes and eye irritations.

Cyanobacteria cell walls contain an endotoxin (lipopolysaccharide) that can irritate any exposed tissue and are capable of eliciting an immune response, including gastrointestinal distress and fever, when exposed to the intestines.

What Do Harmful Algal Blooms Look Like?

Harmful Algal Blooms (HABs) can be caused by many different types of cyanobacteria and therefore can have different appearances. Some HABs look like spilled paint, pea soup, foam, wool, streaks, or floating green globs. Colors may vary from green, blue-green, brown, white, purple, red, and black. Depending on the algae causing the bloom, surface scums may or may not be present and water may simply appear turbid (cloudy or muddy). See the photo gallery for pictures of Harmful Algal Blooms.

What Causes Harmful Algal Blooms?

The exact mechanism for HABs is not well understood. However, in general, algae blooms typically occur during periods of warmer temperatures and increased sunlight, an abundance of nutrients, and low flow conditions.

Water Temperature
Light Availability
Low Wind/Low Flow Conditions
Nutrients (Nitrogen and Phosphorus)

West Virginia HAB Response Plan

A Harmful Algal Bloom Response Plan was developed as a joint effort by the West Virginia Department of Health and Human Resources (DHHR), the West Virginia Department of Environmental Protection, the West Virginia Division of Natural Resources, the U.S. Army Corps of Engineers, and Local Health Departments. The HAB Response Plan provides a unified statewide approach to address HABs in the recreational waters of West Virginia and to protect people and animals from toxins produced by HABs.

Harmful Algal Bloom Response Plan
The principal objective of DHHR’s HAB Response Plan is to provide a unified statewide approach to address HABs in West Virginia’s recreational waters and to protect people and animals from toxins produced by cyanobacteria.

HAB Advisory Levels

In the event of a HAB with cyanotoxin levels above the Recreational Public Health Watch Advisory threshold, a public advisory will be issued and posted with an ORANGE sign. If toxin levels exceed the Recreational Public Health Warning Advisory threshold, a public advisory will be issued and posted with a RED sign. The table below contains the threshold limits for various cyanotoxins. Examples of the advisory signs are included below.

Threshold Level	Microcystin* (µg/L)	Anatoxin-a (µg/L)	Cylindrospermopsin (µg/L)	Saxitoxin* (µg/L)
General Information Signage	< 6	< 80	< 5	< 0.8
Recreational Public Health Watch Advisory	6	80	5	0.8
Recreational Public Health Warning Advisory	20	300	20	3
* Microcystin and saxitoxin thresholds are intended to be applied to total concentrations of all reported variants/congeners of those cyanotoxins.

HAB Advisory Warning Signs

Public advisories are necessary to inform the public of the health risks associated with exposure to water that contains cyanotoxins. The State of West Virginia will issue two levels of advisories for recreational waters based upon the available evidence as described below. It is recommended that all coordinating agencies post (and remove) advisories according to this plan to ensure consistency in messaging.

HAB General Information Sign

Harmful algal bloom general information signs with the following language may be posted for recreational waters with a history of HAB occurrence or upon confirmation of a potential HAB: “Have fun on the water, but know that blue-green algae are present in many of West Virginia’s recreational waters. Their toxins may be, too. Be alert! Avoid water that: looks like spilled paint; has surface scums, mats or films; is discolored or has colored streaks; has green globs floating below the surface Avoid swallowing water.

Recreational Public Health Watch Advisory

When a potential HAB is confirmed and cyanotoxin levels are equal to or exceed the Recreational Public Health Watch Advisory threshold level (6 µg/L for microcystin)(see Appendix 2, Table 2), a Recreational Public Health Watch Advisory will be issued whether or not a HAB is still present. An ORANGE sign (with black lettering) with the following language will be posted: “A harmful algal bloom (HAB) is present and/or algal toxins have been detected in this area. Swimming and wading are not recommended for children, pregnant or nursing women, those with certain medical conditions and pets.

Recreational Public Health Warning Advisory

A Recreational Public Health Warning Advisory will be issued when cyanotoxin levels are equal to or exceed the Recreational Public Health Warning Advisory threshold level (20 µg/L for microcystin)(see Appendix 2, Table 2). A RED sign (with white lettering) with the following language will be posted (see Appendix 12 for public health warning advisory sign template): “Algal toxins at UNSAFE levels have been detected in this area. Swimming, wading and water activities that create spray are not recommended.

Sign depcting general algae information — General Information Signage

Recreational Public Health Watch Advisory

Recreational Public Health Warning Advisory

What Can I Do If I See a Potential Harmful Algal Bloom?

If you see a potential HAB in public recreational waters, report it either through the Algal Bloom Sightings Reporting App or complete an Algal Bloom Report Form and e-mail the form to West Virginia’s HAB mailbox at HAB@wv.gov.

If possible, submit digital photographs. Close-up (within 2 feet) and landscape photographs showing the extent and location of the algal bloom are helpful in HAB identification. HABs reported in non-public (private) waters may be referred to Local Health Departments for assistance. For sampling in private waters, guidance provided in Appendix 7 and Appendix 8 of the HAB Response Plan can be used to collect samples. Samples can be sent to the West Virginia Office of Laboratory Services (OLS). Additional labs that perform phytoplankton identification and cyanotoxin analysis are listed in Appendix 9 of the Response Plan.

Report a Suspected Algal Bloom

Harmful Algal Blooms Reported in West Virginia

HABs that have been reported this year (last updated August 23, 2023):

Reported	Bloom Location		Agency	Investigation Findings	Status
Reported	Waterbody	Watershed	Agency	Investigation Findings	Status
08/21/2023	Rollins Lake	Middle Ohio South	WVDEP	Findings: HAB genera present: Dolichospermum, Microcystis	No Advisory Posted

HAB Health Advisory Legend

No Advisory
Health Watch Advisory: A harmful algal bloom (HAB) is present and/or algal toxins have been detected in this area. Swimming and wading are not recommended for children, pregnant or nursing women, those with certain medical conditions, and pets.
Health Warning Advisory: Algal toxins at UNSAFE levels have been detected in this area. Swimming, wading, and water activities that create spray are not recommended.