Harmful algal blooms, commonly referred to as HABs, occur due to the rapid growth of specific species of algae. HABs are most often the results of cyanobacteria blooms, though other algae species can also form HABs. Certain species of cyanobacteria can produce toxins that can cause severe illness and even death in fish, wildlife, pets, and humans.
Cyanobacteria
Cyanobacteria are microscopic organisms naturally present in lakes worldwide and are one of the most common and abundant microorganisms in freshwater ecosystems. Previously, they were referred to as “blue-green algae,” but they are a type of bacteria capable of photosynthesis. Their unique combination of photosynthetic pigments, which include various types of chlorophyll, carotenoids, and phycobilins, give them a bluish-green appearance, hence the term “blue-green algae.”
Cyanobacteria are an ancient group of organisms and were the first organisms on the planet known to produce oxygen. You can thank cyanobacteria for helping to transform Earth’s atmosphere into an oxygen-rich environment capable of supporting more complex forms of life. The oldest known fossils on Earth are of cyanobacteria, which are referred to as stromatolites. The oldest known stromatolites are from the early Archean eon dating back 3.5 billion years.
Human Health Impacts of a Harmful Algal Bloom
Harmful Algae Produce Toxins
Under specific conditions, certain species of cyanobacteria may produce toxins. These toxins can pose a serious risk of severe illness or death to birds, pets, mammals, and fish. Though not all harmful algal blooms contain toxins, there is no way of telling whether toxins are present without laboratory testing. In addition, toxin presence and concentration can vary significantly from one location to another and over time. Therefore, it is necessary to assume that a harmful algal bloom may be toxic and should be avoided.
There are four toxins commonly found in blooms:
Microcystins
Microcystin is a hepatotoxin that affects the liver, kidneys, and reproductive system. Microcystin is not readily broken down by the body, allowing it to bioaccumulate through the food web. The toxin is absorbed through the gastrointestinal tract into the bloodstream. Abdominal pain, vomiting, diarrhea, headaches, and pneumonia are all potential health effects of exposure to the toxin. In severe cases, especially with smaller animals, hemorrhagic shock is possible. Some studies suggest the toxin is also carcinogenic, but the evidence is limited. The toxin is produced by species belonging to the genera Microcystis, Planktothrix, Dolichospermum, Fisherella, Gloeotrichia, Nodularia, Nostoc, and Oscillatoria. Microcystin is the most common cyanotoxin and is frequently tested for when harmful algal blooms occur.
Cylindrospermopsin
Cylindrospermopsin is a hepatotoxin similar to microcystin; it affects the liver and kidneys. Studies of mice exposed to the toxin showed hemorrhages of the lungs, liver, kidneys, small intestines, and adrenal glands. The toxins are produced by certain species of genera Raphidiopsis, Aphanizomenon, Umezakia, Dolichospermum, and Lyngbya.
Anatoxins
Anatoxins are a type of neurotoxin that affects the central nervous system. Similar to microcystin and Cylindrospermopsin, anatoxins are absorbed by the gastrointestinal tract. The toxin can reduce muscle activity, causing labored breathing, loss of coordination, gasping, convulsioins, and in severe cases, death. The most significant threat is to pets, livestock, and wildlife that drink large quantities of water with the toxin. Certain species of the genera Chrysoporum, Cuspidothrix, Raphidiopsis, Cylindrospermum, Dolichospermum, Microcystis, Oscillitora, Planktothrix, Phormidium, Tychonema, and Woronichinia are capable of producing this toxin.
Saxitoxins
Saxitoxins are commonly associated with paralytic shellfish poisoning (PSP) in marine environments. They are produced by dinoflagellates and certain species of cyanobacteria and can be found in freshwater systems. They are produced by certain species in genera Aphanizomenon, Dolicospermum, Lyngbya, Planktothrix, and Raphidiopsis.
Harmful Algal Blooms Impact on Water Supplies
Cyanotoxins present a significant public health threat to public drinking water supplies. Significant costs can be occurred by municipalities if their water supply is threatened by the presence of cyanotoxins. In addition, public health advisories may be posted warning people with private water systems of the potential danger. HABs can also create taste and odor issues with water, which do not have human health impacts but make water less desirable to consume.
The EPA has established Health Advisories for Microcystins and Cylindrospermopsin under the Safe Drinking Water Act. Heath Advisories are informal guidance for federal, state, and local officials managing water systems. No federal regulations under the Safe Drinking Water Act or Clean Water Act pertain to cyanotoxins.
The threat of harmful algal blooms to water supplies is particularly notable in the Finger Lakes region of New York. The United States Geological Survey (USGS) and the New York State Department of Environmental Conservation (NYS DEC) have deployed advanced equipment in Owasco Lake and Seneca Lake to monitor and study harmful algae on the lakes. HABs are common in many Finger Lakes, providing drinking water to over one million people.
Recreation
HABs threaten not only drinking water supplies but also the recreational use of our freshwater bodies. Swimming, or even boating, through a harmful algal bloom, can result in exposure to toxins. In extreme cases, toxins can be aerosolized and cause respiratory distress. Accidental ingestion of water can harm people, pets, and wildlife. In many cases, dogs are particularly susceptible to toxin exposure from swimming among harmful algae and then licking their coats afterward.
If a harmful algae bloom is present, avoiding swimming in or boating through it is best. An official government organization will often issue a health advisory and close beaches. Closing public beaches can result in significant economic impacts, especially in areas where tourism is a major part of the local economy.
Environmental Impacts of Harmful Algae
Harmful algal blooms, or HABs, are a growing concern for many reasons. Not only can they cause severe illness and death in humans, pets, and wildlife, but they can also significantly impact aquatic ecosystems. For example, HABs can lead to the depletion of dissolved oxygen (DO) levels in water bodies and the death of aquatic life.
When massive blooms of harmful algae die off, they are decomposed by bacteria. The decomposition process utilizes oxygen, which can threaten fish and other forms of aquatic life. Extremely low DO concentrations in a lake result in anoxic conditions, meaning the water lacks sufficient DO to support aquatic life. Large areas of low DO are often referred to as “dead zones” because of the threat they pose to fish and other life.
Lake Erie is well-known because of a large ecological “dead zone” due to algal blooms. At certain times of the year, large swaths of the lake are depleted in oxygen due to algae blooms. Significant efforts have been made to reduce nutrient pollution fueling the algae blooms in the lake.
Economic Impacts of Harmful Algae
Harmful algae can cause extensive property damage and disrupt local economies. As discussed above, HABs can impact drinking water, recreation, and fishing opportunities on a lake. State and federal governments are investing millions of dollars to study and prevent harmful algae from blooming because of concerns over the economic impacts.
As mentioned previously, when HABs affect water supplies, like in the Finger Lakes, municipalities may be forced to spend millions on additional treatment and monitoring. The impacts on recreation can also influence property values, affecting homeowners’ and local government’s tax base.
Environmental Conditions That Lead To HABs
Nutrients
The availability of nutrients, particularly nitrogen and phosphorus, is one of the most critical factors in the formation of harmful algal blooms. HABs are most often associated with freshwater bodies that have nutrient pollution occurring within their watersheds. Therefore, it is particularly important to limit nutrient pollution, reduce phosphorus and nitrogen runoff from farms and limit the use of fertilizers on lawns and gardens.
Warm Temperatures
Harmful algal blooms tend to occur when temperatures and high and there is lots of sunlight. Some research suggests that HABs will become more common due to climate change. In some cases, HABs have been reported on remote water bodies with limited nutrient pollution, and it is believed climate change is one of the primary causes. Warming water temperatures also can impact nutrient cycling within a lake, which may further increase the likelihood of a HAB.
Calm Conditions
Many forms of cyanobacteria have the ability to regulate their buoyancy, a unique adaption among phytoplankton. Blooms typically occur during periods of high temperatures, clear sunny skies, and calm conditions. Slow-moving waters, including those of large rivers, are susceptible to a HAB event. Under these conditions, cyanobacteria can position themselves in the water column to maximize the availability of both light and nutrients.
HABs are often associated with shallow or stagnant water bodies. Periods of drought or low precipitation reduce flushing rates which may result in a proliferation of harmful algae.
Identifying HABs
Identifying a harmful algal bloom can be tricky, as they can vary significantly in appearance. Some HABs may cause the water to appear green, red, or brown. Others may cause the water to foam or form scum on the surface. In some cases, HABs may not impact the appearance of the water at all.
HABs can have many different appearances. Often, they will look like parallel streams or a sheen on the water surface. They are sometimes described as looking like spilled paint that is green, blue, or white in color. They may also look like dense green clumps or globs on the water surface. Finally, they may simply make the water look like a bright green or blue-green color, similar to a pea soup.
If you suspect that a harmful algal bloom is occurring in your area, it is important to report it to state authorities immediately. This will help them track the bloom and take steps to mitigate its impacts. Many states have HAB reporting forms; we’ve listed some below. If your state isn’t listed, contact your state environmental agency to find out if they have a reporting system.
State Reporting Systems
Help Prevent HABs
Lakefront property owners can play a key role in preventing harmful algal blooms from forming. Some simple things you can do to help prevent HABs include:
- Minimizing the amount of fertilizer you use on your lawn
- Properly disposing of pet waste
- Refraining from feeding geese and ducks near lakes and ponds
- Cleaning up after boating activities
- Avoiding using lawn care products that contain phosphorus
HAB prevention isn’t just on the shoulders of lakefront property owners. Everyone living and working in a lake’s watershed has a role to play. For many lakes, excess nutrients from agricultural runoff are a key component of HAB formation. Farmers can follow best management practices to reduce nutrient runoff into local streams that eventually feed a nearby lake.
Climate change is also an increasingly important factor in HAB formation. Everyone can work to make climate-smart decisions in their lives, including choosing more fuel-efficient vehicles, conducting home energy audits, and supporting climate action at the state and federal levels.
Scientific Research
The scientific community also has a role to play. Additional resources are needed to study HABs, the factors that cause their formation, and the human health effects. Scientific research is still needed to determine the specific conditions under which HABs occur. Many state and federal agencies, along with their university partners, are working to study how human activities and environmental factors lead to the formation of HABs. This research is particularly important for predicting HABs before forming so that water treatment facilities and residents can prepare.
Conclusions
Harmful algal blooms are a serious problem. By taking some simple steps to prevent their formation, we can help protect our lakes, rivers, and streams for future generations. We also need to support the scientific research necessary to understand how HABs impact the environment and human health. With a rapidly changing climate, there is even greater potential for HABs to form in lakes that were previously thought to be at low risk.
