Harmful Algal Blooms

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What is a Harmful Algal Bloom (HAB)?
What are the effects of cyanotoxins?
What do harmful algal blooms look like?
What causes harmful algal blooms?
What is the WVDEP doing to address harmful algal blooms?
What can I do if I see a potential harmful algal bloom?
Have any harmful algal blooms been reported in West Virginia?
Where can I view a list of previous HABs that have been reported in West Virginia?


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. Click here to see micrographs of common HAB-capable species of cyanobacteria and species-specific bloom descriptions.

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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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.

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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.

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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)

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What is the WVDEP doing to address harmful algal blooms?

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. This plan can be found here.

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.

General Information Signage Recreational Public Health Watch Advisory Recreational Public Health Warning Advisory

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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 website http://tagis.dep.wv.gov/algae or complete an Algal Bloom Report Form and e-mail the form to West Virginia’s HAB mailbox at HAB@wv.gov. The form can be found here and in Appendix 5 of the HAB Response Plan.

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.

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Have any harmful algal blooms been reported in West Virginia?

Below are HABs that have been reported this year (last updated September 8, 2020).

Reported Bloom Location Agency Investigation Findings Status
Waterbody Watershed
 8/31/2020 Private Pond/Wheeling  Upper Ohio  WVDEP  non-cyanobacteria HAB genera present: Euglena.  Cyanobacteria HAB general present: Cuspidothrix issatschenkoi, Microcystis No Advisory Posted 
 8/24/2020 Private Pond #2/Grafton Tygart  WVDEP HAB genera present: Cylindrospermopsis, Pseudanabaena/Limnothrix  No Advisory Posted
8/21/2020 Burnsville Lake Dam Tailwaters Little Kanawha WVDEP HAB general present: Dolichospermum with small amount of Microcystis No Advisory Posted
 8/17/2020 Riverlake Estates Lake (private) Coal WVDEP  non-cyanobacteria HAB genera present: Euglena.  Cyanobacteria HAB genera present: small amounts of Cylindrospermopsis, Microcystis No Advisory Posted
8/17/2020 Little Kanawha River, near Tygart Creek Little Kanawha WVDEP "bloom" dominated by non-algae: Watermeal. Note: a few small amount of Dolichospermum and Raphidiopsis present No Advisory Posted
 8/17/2020 Private Pond/Willow Island  Ohio  WVDEP non-cyanobacteria HAB genera present: Euglena sp.   No Advisory Posted
 8/12/2020 Private Pond/Grafton  Tygart  WVDEP bloom dominated by non-HAB green algae: Sphaerocystis.  Note: a small amount of cyanobacteria Phormidium present  No Advisory Posted
 8/10/2020 Alpine Lake (private) Youghiogheny   WVDEP non-cyanobacteria HAB genera present: Euglena  No Advisory Posted


HAB Advisory Maps

There are no current HAB Advisories. If a HAB Advisory were in place a map would appear below.


HAB Cyanotoxin Data

Below are links to view cyanotoxin data for blooms reported in 2020.

Private Pond in/near Wheeling, Upper Ohio River drainage, Ohio County

Private Pond #2 in/near Grafton, Tygart River drainage, Taylor County

Burnsville Lake Dam Tailwaters, Little Kanawha River drainage, Braxton County

Riverlake Estates Lake (private), Coal River drainage, Kanawha County

Little Kanawha River near Tygart Creek, Little Kanawha River drainage, Wood County

Private Pond #1 in/near Grafton, Tygart River drainage, Braxton County


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