HABs FAQs
Frequently Asked Questions about Harmful Algal Blooms
Impacts of Harmful Algal Blooms (HABs)
What are the impacts of Harmful Algal Blooms (HABs)?
Harmful algal blooms (HABs) have far-reaching impacts on ecosystems, human health, and economies. HABs can harm the environment through the production of potent toxins that disrupt ecosystems, harm aquatic life and contaminate the food web. Even blooms that do not produce toxins can cause harm by depleting oxygen levels, leading to dead zones and fish kills. Marine mammals, such as manatees, dolphins, and sea lions, are particularly vulnerable to algal toxins, which can cause illness, disorientation, or death. Human health is directly impacted through toxic seafood consumption, respiratory irritation from aerosolized toxins, and skin irritation from contact with contaminated water. Economically, HABs cause significant losses in fisheries, aquaculture, and tourism while increasing costs for monitoring and mitigation. They also pose social challenges by reducing access to clean water and safe seafood, disproportionately affecting vulnerable communities.
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Are toxins always present during a HAB event?
It depends on the species populating the bloom and the environmental conditions. Toxins are not always present during a harmful algal bloom (HAB) event, as species that produce toxins can vary their production depending on several factors. While some algae species produce harmful toxins, not all species involved in a bloom are toxin-producing, and even toxin-producing species may not always produce toxins. Environmental conditions such as nutrient levels (particularly nitrogen and phosphorus), light, temperature, salinity, pH and biological interactions can influence toxin production. Additionally, stress factors including ecological resource competition or changes in water chemistry may either enhance or suppress toxin synthesis. This variability underscores the importance of monitoring both algal biomass and toxin levels to assess the risks associated with HABs accurately.
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Do HAB events always discolor the water?
Harmful algal blooms (HABs) can discolor the water green, blue, orange, brown, or red but also can be colorless. The color and intensity of a bloom depends on the specific types of algae causing the HAB. It is important to remember that some HAB are not brightly colored and may be difficult to see. Most often the “red tide” is the most recognizable harmful bloom in marine waters, as its name suggests; it is characterized by shades of red and brown caused by species of phytoplankton (most commonly dinoflagellates). The concentration of these algae cells contain pigments that give off its respective appearance, when large quantities of cells containing photosynthetic pigments are present in marine waters, the color will appear more intense.
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Types of Harmful Algal Blooms (HABs)
Are all types of HABs the same?
HABs are very diverse and can be caused by a variety of different types of algae. There are numerous types of harmful species that commonly bloom in different aquatic environments and in different geographic regions. In marine waters, there are two types of phytoplankton that are mostly commonly responsible for HABs: dinoflagellates and diatoms. Cyanobacteria is a plant-like bacteria that is sometimes found in marine waters, but most commonly blooms in freshwater and estuarine environments.
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What types of HABs are the most common along the U.S. West Coast?
The most common harmful algal blooms (HABs) along the U.S. West Coast are caused by species that produce domoic acid, saxitoxins, and okadaic acid. Pseudo-nitzschia (a diatom) produces domoic acid, which causes amnesic shellfish poisoning (ASP) and is often associated with nutrient-rich upwelling events. Alexandrium (a dinoflagellate) produces saxitoxins, responsible for paralytic shellfish poisoning (PSP), and thrives in warmer, nutrient-enriched coastal waters. Dinophysis (another dinoflagellate) produces okadaic acid, leading to diarrhetic shellfish poisoning (DSP), and typically blooms in calm, stratified waters. These species pose significant risks to marine life, human health, and shellfish industries.
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Are there other types of HABs on the West Coast that are of emerging concern?
Several emerging HAB types are occurring along the U.S. West Coast. Several species of dinoflagellates have bloomed including Lingulodinium, Akashiwo, and Prorocentrum have been linked to HAB events. Other types of phytoplankton like raphidophytes, in particular Heterosigma and Chattonella, have been documented to cause harmful impacts to fisheries and wildlife. Additionally, blooms of cyanobacteria, which are most prevalent in freshwater and estuarine environments, produce cyanotoxins which can be transferred through the watershed into coastal areas. Cyanotoxins have been found in coastal seafood and have cause mortality events in wildlife such as Southern Sea Otters.
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Do HABs only occur in the ocean?
Harmful algal blooms (HABs) can occur in a variety of aquatic systems including in marine, estuarine, and freshwater systems. In freshwater, cyanobacteria (sometimes also called blue-green algae) are responsible for most HAB events. Notably, cyanobacterial HABs have been documented in all 50 states in the U.S. Notably, these types of HAB have been found in all 50 states in the U.S. Many types of cyanobacteria have the ability to produce toxins, known as cyanotoxins. The most common cyanobacteria that produces harmful blooms is called Microcystis and produces a suite of cyanotoxins called microcystins.
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Causes of Harmful Algal Blooms (HABs)
What causes HABs?
There are many factors that contribute to the formation of HAB events, including physical, chemical and biological factors. Some of the main factors include: nutrient levels, water temperature, salinity, water flow, and pH. High levels of nutrients in water can promote the formation of HABs by supporting high levels of phytoplankton growth. Nutrient enrichment can be caused through a variety of factors including anthropogenic factors like pollution. One of the emerging factors is climate change and global warming. Since many HAB forming species thrive in warm waters, climate change is expected to increase bloom occurrences and severity.
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Does nutrient pollution cause HABs?
Yes, nutrient pollution is one of the most critical factors involved in HAB events. Nutrient pollution includes increased amounts of nitrogen and phosphorus in water, and this is often a result of agricultural and urban runoff. These nutrients are derived from fertilizers, sewage, and overland runoff. Nutrient pollution can increase the growth of many types of algae, which, in turn, increases their density in the water and increases the likelihood of a HAB event.
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How is climate change anticipated to affect HABs?
Climate change is anticipated to increase the incidence of HAB events in the future. Climate fluctuations are expected to lead to an increase in air and water temperature, these water conditions combined with stormwater runoff are preferable growing conditions for many species that form HABs.
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HABs Monitoring
What are the different ways to identify when a HAB event occurs?
Harmful algal bloom (HAB) events can be identified through a variety of approaches. One of the most common methods is the collection of water samples from the environment for species identification, pigment analysis, and toxin detection. Another common approach is to establish continuous monitoring stations to measure factors such as photosynthetic pigments, temperature, salinity, and dissolved oxygen using buoy-based or moored sensors. More advanced technologies, such at as underwater, autonomous microscopes are also becoming increasingly used to automatically collect and image water samples, looking for HAB forming species. More advanced molecular techniques that utilize environmental DNA are also being used increasingly to detect HAB events. Remote sensing technologies, such as satellite imagery and ocean color sensors, complement these efforts by detecting algal pigments and temperature anomalies over larger areas. Monitoring data is also used in computer forecasting models in an effort to predict when a HAB event might occur in the future.
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What systems are in place to monitor for HABs?
Multiple monitoring systems are in place along the U.S. West Coast to detect harmful algal blooms (HABs). Public health monitoring is conducted by all West Coast states and Tribes to protect against the consumption of seafood contaminated with HAB toxins. Additional HAB monitoring is conducted to detect the initiation of HAB events through collaborative networks including California Harmful Algal Bloom Monitoring and Alert Program (Cal-HABMAP) and Olympic Region Harmful Algal Bloom (ORHAB) Partnership. Community science initiatives (such as NOAA’s Phytoplankton Monitoring Network) and marine mammal stranding networks further enhance detection and response efforts.
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What types of technologies are being developed to enhance HABs monitoring?
Newer technologies and monitoring initiatives include the development of predictive models and the establishment of autonomous monitoring systems that utilize novel robotics approaches. Some recent examples of these efforts include the California Imaging Flowcytobot Network (CA IFCB Network) and California-Harmful Algae Risk Mapping (C-HARM), which have been developed in recent years to further enhance these monitoring efforts and support more rapid detection, tracking, and prediction of HAB events.
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Bioluminescence
Is bioluminescence a harmful algal bloom event?
Bioluminescence occurs when there is an abundance of algae containing specific dinoflagellate species (a type of plankton) that have the ability to bioluminesce (emit light). When a bioluminescent algae is disturbed, it emits a blue glow caused by a chemical reaction between the algae and oxygen. A bioluminescent bloom alone does not indicate whether the algae is releasing toxins. This is because there are many types of dinoflagellates that can produce bioluminescence, some are harmful to humans and animals, while others are not. The toxicity of a bioluminescent bloom depends on the specific type of dinoflagellates in the water, and whether the right conditions were met in order for toxins to be produced.
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Photo Credits: Woods Hole Oceanographic Institution and California HABMap.