Harmful algal blooms (HABs) are caused by a complex set of physical, chemical, biological, hydrological, and meteorological conditions. Many unanswered questions remain about occurrence, environmental triggers for toxicity, and the ability to predict the timing, duration, and toxicity of HABs.
Freshwater and marine algal blooms can be called harmful because they lower dissolved oxygen concentrations, alter aquatic food webs, leave ugly scums along shorelines, produce taste-and-odor compounds that cause drinking water and fish flesh to taste bad, or produce toxins so potent they poison organisms in the water and on the land.
Building knowledge to protect the Nation's water quality
Many different types of algae can cause harmful algal blooms (HABs) in freshwater ecosystems. The most frequent and severe blooms typically are caused by cyanobacteria, the only known freshwater algae with the potential for production of toxins potent enough to harm human health. Cyanobacterial harmful algal blooms (cyanoHABs) are of increasing global concern. CyanoHABs can threaten human and aquatic ecosystem health. Economic damages related to cyanoHABs include the loss of recreational revenue, decreased property values, and increased drinking-water treatment costs.
Nationwide, toxic freshwater cyanobacterial harmful algal blooms have been implicated in human and animal illness and death in at least 43 states. In August 2016, at least 19 states had public health advisories because of cyanoHABs.
What are cyanobacteria?
Cyanobacteria are naturally occurring microscopic organisms. Although they are true bacteria, they function more like algae in aquatic ecosystems. For that reason, they typically are considered to be part of algal communities, which is why they often are called "blue-green algae". Cyanobacterial blooms can appear as discolorations in the water or paint-like scums at the water surface. Typically, the blooms are blue-green in color, but they also can be yellow, red, or brown.
Cyanobacteria are notorious for producing a variety of compounds with water-quality concerns. Cyanobacteria produce taste-and-odor compounds that people are sensitive to at very low concentrations (even parts per trillion) in drinking water. Taste-and-odor compounds can accumulate in fish flesh making taste bad, an important concern for the aquaculture industry.
Of greater concern than unpleasant taste and odor is the production of toxins that affect human health. Human ingestion, inhalation, or contact with water containing elevated concentrations of cyanotoxins can cause allergic reactions, dermatitis, gastroenteritis, and seizures.
Understanding cyanoHABs
USGS National Water-Quality Program scientists are leading a diverse range of studies to address cyanoHAB issues in water bodies throughout the United States, using a combination of traditional methods and emerging technologies in collaboration with numerous partners. However, despite advances in scientific understanding of cyanobacteria and associated compounds, many questions remain unanswered about the occurrence of cyanoHABs, the environmental triggers for toxicity, and the ability to predict the timing and toxicity of cyanoHABs.
Advanced warnings at time scales relevant to cyanoHAB management (hours to days) would allow proactive, rather than reactive, responses to potential events. Sensors that measure cyanobacteria in near real-time show promise for use in early warning systems.
The ability for cyanobacteria to produce cyanotoxins as well as taste-and-odor compounds is caused by genetic distinctions. By analyzing those distinctions, we can gain a greater understanding of the world of cyanoHABs, an understanding that may lead us to new ways to combat this threat. USGS is developing field and laboratory methods to quantify cyanobacteria and associated compounds that include field protocols, field guides, sample preparation techniques, development of assays, and molecular tools.
Nutrient enrichment: A key factor in occurrences of cyanoHABs
One of the key causes of cyanoHABs is nutrient enrichment. When nutrients from agricultural and urban areas are transported downstream, they can cause cyanoHABs that can impair drinking-water quality and require closure of recreational areas.
The USGS, in cooperation with local, state, federal, tribal, and university partners, is pioneering new monitoring, assessment, and modeling approaches to better understand nutrient sources, their transport, and their role in cyanoHABs development.
Tracking the water quality of the nation’s streams and rivers
The USGS monitors nutrient concentrations and flux at key sites nationwide. Annual data are featured at the website, Tracking Water Quality of the Nation's Rivers and Streams.
In addition, the USGS uses advanced optical sensor technology to track nitrate levels in real time at more than 140 sites nationwide. These data provide real-time information, improve load calculations, and advance our understanding of processes controlling nutrient variability. The data are publicly available at the website, WaterQuality Watch.
Identifying Nutrient Sources and Hotspots
USGS models of nutrient concentrations and loads in streams provide an important tool for identifying nutrient sources. Estimates derived from these models provide insights into which areas and sources are contributing the largest amounts of nutrients to local streams, lakes, and reservoirs. The models also enable the tracking of nutrients and their sources from local streams to the Nation’s estuaries and the Great Lakes. See website, Tracking the Source and Quantity of Nutrients to the Nation's Estuaries.
Other USGS HABs Research
U.S. Geological Survey Environmental Health Toxins and Harmful Algal Blooms Research Team
Follow the links below to find additional web pages on HABs.
Harmful Algal Bloom Toxins in Alaska Seabirds
Harmful Algal Bloom (HAB) Cooperative Matching Funds Projects
Harmful Algal Bloom monitoring in the Finger Lakes region, New York
Are Naturally Occurring Algal Toxins in Water Resources a Health Hazard?
Algal and Other Environmental Toxins — Lawrence, Kansas
Harmful Algal Blooms (HABs)
Harmful Algae Blooms (HABs)
Cyanobacterial (Blue-Green Algal) Blooms: Tastes, Odors, and Toxins
Follow the links below to access data or web applications associated with harmful algal blooms, cyanotoxins, and cyanobacteria.
Data and model archive for multiple linear regression models for prediction of weighted cyanotoxin mixture concentrations and microcystin concentrations at three recurring bloom sites in Kabetogama Lake in Minnesota
Find links to publications on harmful algal blooms, cyanotoxins, and cyanobacteria below.
Cyanotoxin mixture models: Relating environmental variables and toxin co-occurrence to human exposure risk
Toxic cyanobacterial blooms, often containing multiple toxins, are a serious public health issue. However, there are no known models that predict a cyanotoxin mixture (anatoxin-a, microcystin, saxitoxin). This paper presents two cyanotoxin mixture models (MIX) and compares them to two microcystin (MC) models from data collected in 2016–2017 from three recurring cyanobacterial bloom locations in Ka
Cyanotoxin occurrence in large rivers of the United States
Cyanotoxins occur in rivers worldwide but are understudied in lotic ecosystems relative to lakes and reservoirs. Eleven large river sites located throughout the United States were sampled during June–September 2017 to determine the occurrence of cyanobacteria with known cyanotoxin-producing strains, cyanotoxin synthetase genes, and cyanotoxins. Chlorophyll-a concentrations spanned the range from o
Cyanobacterial harmful algal blooms and U.S. Geological Survey science capabilities
Field and laboratory guide to freshwater cyanobacteria harmful algal blooms for Native American and Alaska Native communities
Relations between DNA- and RNA-based molecular methods for cyanobacteria and microcystin concentration at Maumee Bay State Park Lakeside Beach, Oregon, Ohio, 2012
Water samples were collected from Maumee Bay State Park Lakeside Beach, Oregon, Ohio, during the 2012 recreational season and analyzed for selected cyanobacteria gene sequences by DNA-based quantitative polymerase chain reaction (qPCR) and RNA-based quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Results from the four DNA assays (for quantifying total cyanobacteria, total M
Comparison of two cell lysis procedures for recovery of microcystins in water samples from silver lake in Dover, Delaware, with microcystin producing cyanobacterial accumulations
Below are news stories associated with this project.
- Overview
Harmful algal blooms (HABs) are caused by a complex set of physical, chemical, biological, hydrological, and meteorological conditions. Many unanswered questions remain about occurrence, environmental triggers for toxicity, and the ability to predict the timing, duration, and toxicity of HABs.
Freshwater and marine algal blooms can be called harmful because they lower dissolved oxygen concentrations, alter aquatic food webs, leave ugly scums along shorelines, produce taste-and-odor compounds that cause drinking water and fish flesh to taste bad, or produce toxins so potent they poison organisms in the water and on the land.
Building knowledge to protect the Nation's water quality
Many different types of algae can cause harmful algal blooms (HABs) in freshwater ecosystems. The most frequent and severe blooms typically are caused by cyanobacteria, the only known freshwater algae with the potential for production of toxins potent enough to harm human health. Cyanobacterial harmful algal blooms (cyanoHABs) are of increasing global concern. CyanoHABs can threaten human and aquatic ecosystem health. Economic damages related to cyanoHABs include the loss of recreational revenue, decreased property values, and increased drinking-water treatment costs.
Nationwide, toxic freshwater cyanobacterial harmful algal blooms have been implicated in human and animal illness and death in at least 43 states. In August 2016, at least 19 states had public health advisories because of cyanoHABs.
Toxic cyanobacterial harmful algal blooms (CyanoHABs) have been implicated in human and animal illness and death in at least 43 States in the United States. In August 2016, at least 19 States had public health advisories because of CyanoHABs. What are cyanobacteria?
Cyanobacteria are naturally occurring microscopic organisms. Although they are true bacteria, they function more like algae in aquatic ecosystems. For that reason, they typically are considered to be part of algal communities, which is why they often are called "blue-green algae". Cyanobacterial blooms can appear as discolorations in the water or paint-like scums at the water surface. Typically, the blooms are blue-green in color, but they also can be yellow, red, or brown.
Cyanobacteria are notorious for producing a variety of compounds with water-quality concerns. Cyanobacteria produce taste-and-odor compounds that people are sensitive to at very low concentrations (even parts per trillion) in drinking water. Taste-and-odor compounds can accumulate in fish flesh making taste bad, an important concern for the aquaculture industry.
Of greater concern than unpleasant taste and odor is the production of toxins that affect human health. Human ingestion, inhalation, or contact with water containing elevated concentrations of cyanotoxins can cause allergic reactions, dermatitis, gastroenteritis, and seizures.
Understanding cyanoHABs
USGS National Water-Quality Program scientists are leading a diverse range of studies to address cyanoHAB issues in water bodies throughout the United States, using a combination of traditional methods and emerging technologies in collaboration with numerous partners. However, despite advances in scientific understanding of cyanobacteria and associated compounds, many questions remain unanswered about the occurrence of cyanoHABs, the environmental triggers for toxicity, and the ability to predict the timing and toxicity of cyanoHABs.
Advanced warnings at time scales relevant to cyanoHAB management (hours to days) would allow proactive, rather than reactive, responses to potential events. Sensors that measure cyanobacteria in near real-time show promise for use in early warning systems.
The ability for cyanobacteria to produce cyanotoxins as well as taste-and-odor compounds is caused by genetic distinctions. By analyzing those distinctions, we can gain a greater understanding of the world of cyanoHABs, an understanding that may lead us to new ways to combat this threat. USGS is developing field and laboratory methods to quantify cyanobacteria and associated compounds that include field protocols, field guides, sample preparation techniques, development of assays, and molecular tools.
Nutrient enrichment: A key factor in occurrences of cyanoHABs
One of the key causes of cyanoHABs is nutrient enrichment. When nutrients from agricultural and urban areas are transported downstream, they can cause cyanoHABs that can impair drinking-water quality and require closure of recreational areas.
The USGS, in cooperation with local, state, federal, tribal, and university partners, is pioneering new monitoring, assessment, and modeling approaches to better understand nutrient sources, their transport, and their role in cyanoHABs development.
Illustration of nutrient sources of cyanobacterial harmful algal blooms. Tracking the water quality of the nation’s streams and rivers
The USGS monitors nutrient concentrations and flux at key sites nationwide. Annual data are featured at the website, Tracking Water Quality of the Nation's Rivers and Streams.
In addition, the USGS uses advanced optical sensor technology to track nitrate levels in real time at more than 140 sites nationwide. These data provide real-time information, improve load calculations, and advance our understanding of processes controlling nutrient variability. The data are publicly available at the website, WaterQuality Watch.
Identifying Nutrient Sources and Hotspots
USGS models of nutrient concentrations and loads in streams provide an important tool for identifying nutrient sources. Estimates derived from these models provide insights into which areas and sources are contributing the largest amounts of nutrients to local streams, lakes, and reservoirs. The models also enable the tracking of nutrients and their sources from local streams to the Nation’s estuaries and the Great Lakes. See website, Tracking the Source and Quantity of Nutrients to the Nation's Estuaries.
New technology is helping the USGS monitor harmful algal blooms. Other USGS HABs Research
U.S. Geological Survey Environmental Health Toxins and Harmful Algal Blooms Research Team
- Science
Follow the links below to find additional web pages on HABs.
Harmful Algal Bloom Toxins in Alaska Seabirds
Elevated ocean temperatures are linked to the development of harmful algal blooms (HABs). Toxins from these blooms may pose health threats to marine organisms, including seabirds. Since 2015, the USGS has worked with a variety of stakeholders to develop testing methods and research projects to better understand the geographic extent, timing and impacts of algal toxins in Alaska marine ecosystems...Harmful Algal Bloom (HAB) Cooperative Matching Funds Projects
New projects from coast to coast will advance the research on harmful algal blooms (HABs) in lakes, reservoirs and rivers. The vivid emerald-colored algal blooms are caused by cyanobacteria, which can produce cyanotoxins that threaten human health and aquatic ecosystems and can cause major economic damage.Harmful Algal Bloom monitoring in the Finger Lakes region, New York
Background: Harmful algal blooms (HABs) are increasingly a global concern because they pose a threat to human and aquatic ecosystem health and cause economic damages. Cyanobacterial HABs (CyanoHABs) represent a substantial threat to drinking-water supplies, aquatic ecosystem health, and safe recreational uses of freshwater resources in New York. Toxins produced by some species of cyanobacteriaAre Naturally Occurring Algal Toxins in Water Resources a Health Hazard?
A growing number of human gastrointestinal, respiratory, dermatologic, and neurologic effects, as well as dog and livestock illnesses and deaths, in the United States have been linked to exposures to algal blooms in recreational lakes and stock ponds. Some of the blooms contain cyanobacteria, which have the potential to produce cyanotoxins in freshwater systems. However, the connection between...Algal and Other Environmental Toxins — Lawrence, Kansas
About the Laboratory The Environmental Health Program collaborates with scientists at the Organic Geochemistry Research Laboratory (OGRL) in Lawrence, Kansas, to develop and employ targeted and non-targeted analytical methods for identification and quantitation of known and understudied algal/cyanobacterial toxins. The laboratory contructed in 2019 is a 2,500 square foot modern laboratory facility...Harmful Algal Blooms (HABs)
The USGS collaborates with local, state, federal, tribal, university, and industry partners to conduct the science necessary to understand the causes and effects of toxic HABs and inform water management and public health decisions. USGS is characterizing the life cycle of HABs, their asociated toxins, and the genes responsible for cyanotoxin production. This work is enhancing the ability of Great...Harmful Algae Blooms (HABs)
Cyanobacterial harmful algal blooms (HABs) are increasingly a global concern because HABs pose a threat to human and aquatic ecosystem health and cause economic damages. Toxins produced by some species of cyanobacteria (called cyanotoxins) can cause acute and chronic illnesses in humans and pets. Aquatic ecosystem health also is affected by cyanotoxins, as well as low dissolved oxygen...Cyanobacterial (Blue-Green Algal) Blooms: Tastes, Odors, and Toxins
Freshwater and marine harmful algal blooms (HABs) can occur anytime water use is impaired due to excessive accumulations of algae. In freshwater, the majority of HABs are caused by cyanobacteria (also called blue-green algae). Cyanobacteria cause a multitude of water-quality concerns, including the potential to produce taste-and-odor causing compounds and toxins that are potent enough to poison... - Data
Follow the links below to access data or web applications associated with harmful algal blooms, cyanotoxins, and cyanobacteria.
Data and model archive for multiple linear regression models for prediction of weighted cyanotoxin mixture concentrations and microcystin concentrations at three recurring bloom sites in Kabetogama Lake in Minnesota
Multiple linear regression models were developed using data collected in 2016 and 2017 from three recurring bloom sites in Kabetogama Lake in northern Minnesota. These models were developed to predict concentrations of cyanotoxins (anatoxin-a, microcystin, and saxitoxin) that occur within the blooms. Virtual Beach software (version 3.0.6) was used to develop four models: two cyanotoxin mixture (MI - Multimedia
- Publications
Find links to publications on harmful algal blooms, cyanotoxins, and cyanobacteria below.
Cyanotoxin mixture models: Relating environmental variables and toxin co-occurrence to human exposure risk
Toxic cyanobacterial blooms, often containing multiple toxins, are a serious public health issue. However, there are no known models that predict a cyanotoxin mixture (anatoxin-a, microcystin, saxitoxin). This paper presents two cyanotoxin mixture models (MIX) and compares them to two microcystin (MC) models from data collected in 2016–2017 from three recurring cyanobacterial bloom locations in Ka
AuthorsVictoria Christensen, Erin Stelzer, Barbara C. Scudder Eikenberry, Hayley T. Olds, Jaime F. LeDuc, Ryan P. Maki, Jack E. Norland, Eakalak KhanCyanotoxin occurrence in large rivers of the United States
Cyanotoxins occur in rivers worldwide but are understudied in lotic ecosystems relative to lakes and reservoirs. Eleven large river sites located throughout the United States were sampled during June–September 2017 to determine the occurrence of cyanobacteria with known cyanotoxin-producing strains, cyanotoxin synthetase genes, and cyanotoxins. Chlorophyll-a concentrations spanned the range from o
AuthorsJennifer L. Graham, Neil Dubrovsky, Guy Foster, Lindsey R. King, Keith Loftin, Barry Rosen, Erin StelzerCyanobacterial harmful algal blooms and U.S. Geological Survey science capabilities
Cyanobacterial harmful algal blooms (CyanoHABs) are increasingly a global concern because CyanoHABs pose a threat to human and aquatic ecosystem health and cause economic damages. Despite advances in scientific understanding of cyanobacteria and associated compounds, many unanswered questions remain about occurrence, environmental triggers for toxicity, and the ability to predict the timing, duratAuthorsJennifer L. Graham, Neil M. Dubrovsky, Sandra M. EbertsField and laboratory guide to freshwater cyanobacteria harmful algal blooms for Native American and Alaska Native communities
Cyanobacteria can produce toxins and form harmful algal blooms. The Native American and Alaska Native communities that are dependent on subsistence fishing have an increased risk of exposure to these cyanotoxins. It is important to recognize the presence of an algal bloom in a waterbody and to distinguish a potentially toxic harmful algal bloom from a non-toxic bloom. This guide provides field imaAuthorsBarry H. Rosen, Ann St. AmandRelations between DNA- and RNA-based molecular methods for cyanobacteria and microcystin concentration at Maumee Bay State Park Lakeside Beach, Oregon, Ohio, 2012
Water samples were collected from Maumee Bay State Park Lakeside Beach, Oregon, Ohio, during the 2012 recreational season and analyzed for selected cyanobacteria gene sequences by DNA-based quantitative polymerase chain reaction (qPCR) and RNA-based quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Results from the four DNA assays (for quantifying total cyanobacteria, total M
AuthorsErin A. Stelzer, Keith A. Loftin, Pamela StruffolinoComparison of two cell lysis procedures for recovery of microcystins in water samples from silver lake in Dover, Delaware, with microcystin producing cyanobacterial accumulations
A collaboration was developed between Abraxis, LLC, the State of Delaware Department of Natural Resources and Environmental Control Division of Water Resources Environmental Laboratory, the University of Delaware, and the United States Geological Survey to investigate the efficacy of the QuikLyse procedure developed by Abraxis, LLC as an alternative cell-lysis technique suitable for use with an exAuthorsKeith A. Loftin, Michael T. Meyer, Fernando Rubio, Lisa Kamp, Edythe Humphries, Ed Whereat - News
Below are news stories associated with this project.