About Algae Blooms

Causes of HABs

Dangers of HABs

Safety Precautions

Preventing HABs

Causes of HABs

What causes an algal bloom? - There is no single factor which causes an algal bloom. A combination of optimum factors such as the presence of good nutrients, warm temperatures and lots of light all encourage the natural increase in numbers of blue-green algae in our waterways. Nature mostly takes care of the temperature and light, but the increased presence of nutrients such as phosphorous is largely due to poor farming practices such as high use of fertilizers and presence of livestock near water supplies, as well as effluent and run-off from towns and cities near waterways. The ponding of water and reducing river flow rates tends to improve the light and sometimes the nutrient environment for algal growth making water turbulance a major factor in bloom develpment. Pesticides and other chemicals may affect the natural grazers which would otherwise control algal growth and their presence increases the risk of blooms.

How do cyanobacterial blooms form? - Cyanobacterial blooms occur when algae that are normally present grow exuberantly. Within a few days, a bloom can cause clear water to become cloudy. The blooms usually float to the surface and can be many inches thick, especially near the shoreline. Cyanobacterial blooms can form in warm, slow-moving waters that are rich in nutrients such as fertilizer runoff or septic tank overflows. Blooms can occur at any time, but most often occur in late summer or early fall. They can occur in marine, estuarine, and fresh waters, but the blooms of greatest concern are the ones that occur in fresh water, such as drinking water reservoirs or recreational waters.

I've heard zebra mussels are causing the blooms. How does that work? - Zebra mussels have been implicated as a factor promoting the formation of harmful algae blooms in the Great Lakes region, particularly for low-phosphorus inland lakes. By removing natural competitors (green algae) and/or altering the chemical composition of the water, zebra mussels may promote HABs. Zebra mussels have been shown to be capable of selecting which algae they consume -- spitting out presumably toxic forms such as Microcystis. By filtering the water, zebra mussels also increase the amount of light reaching the bottom of the lake, which promotes the growth of large benthic forms of algae such as Cladophora which may break free during storms or due to wave action to form floating mats or to wash up on the beaches.

Can you get a blue-green algal bloom in winter? - Yes, however, this is less likely than in summer. Algal blooms can occur any time of year as long as the conditions such as, temperature and nutrients , are right for growing.

Dangers of HABs

What are the dangers of blue-green algae? -

• They spoil water quality when present in large numbers by producing odours or thick scums.
• They can make drinking water smell and taste bad.
• They can make recreational areas unpleasant.
• Dense blooms can block sunlight killing other plants and animals.
• When algae decompose they may use up oxygen in the water and cause fish kills.
• Some cyanobacteria that can produce toxins that are among the most powerful natural poisons known. These toxins have no known antidotes. The toxins are poisonous to humans and may be deadly to livestock and pets.
• CyanoHABs can make people, their pets, and other animals sick. Often, the first sign that an HAB exists is a sick dog that has been swimming in an algae-filled pond. Children are at higher risk than adults for illness from CyanoHABs because they weigh less and can get a relatively larger dose of toxin.

Are all blue-green algae poisonous? - No. There are many species of Blue-green algae. Some are not known to have any toxins, others have one or more different types of toxin. Species known to be toxic may only be toxic at certain times and places within a bloom. Blue-green algae are a natural part of all waterways. Under certain conditions some blue-green algae multiply to bloom levels and may produce toxins which are dangerous to stock and humans.

What species of cyanobacteria form harmful algal blooms in fresh water? - The most common HAB in the Great Lakes region are...

• Microcystis aeruginosa
• Anabaena circinalis
• Anabaena flos-aquae
• Aphanizomenon flos-aquae
• Cylindrospermopsis raciborskii
  

What are the toxins they produce? - Toxins page

What types of illnesses can people and animals get from exposure to HABs? -

• Getting it on the skin may give people a rash, hives, or skin blisters (especially on the lips and under swimsuits).
• Inhaling water droplets from irrigation or water-related recreational activities can cause runny eyes and nose, a sore throat, asthma-like symptoms, or allergic reactions.
• Swallowing water that has toxins in it can cause:
  • Acute, severe gastroenteritis (including diarrhea and vomiting).
  • Liver toxicity (i.e., increased serum levels of liver enzymes). Symptoms of liver poisoning may takes hours or days to show up in people or animals. Symptoms include abdominal pain, diarrhea, and vomiting.
    Kidney toxicity.
  • Neurotoxicity. These symptoms can appear within minutes after exposure. In dogs, the neurotoxins can cause salivation and other neurologic symptoms, including weakness, staggering, difficulty breathing, convulsions, and death. People may have numb lips, tingling fingers and toes, or they may feel dizzy.
  • Paralytic shellfish poisoning (PSP). PSP is caused by consumption of shellfish (e.g., mussels and clams) which bioaccumulate a toxin produced by dinoflagellates (red tide). Dinoflagellates similar to those responsible for PSP are occassionally found in the Great Lakes, but dangerous levels of PSP toxin have not been observed here.
    

How could you be exposed to HABs and toxins? -

• Drinking water that comes from a lake or reservoir with a HAB.
• Drinking untreated water.
• Engaging in recreational activities in waters with HABs.
• Inhaling aerosols from water-related activities such as jet-skiing or boating.
• Inhaling aerosols when watering lawns, irrigating golf-courses, etc. with pond water.
• Using cyanobacteria-based dietary supplements that are contaminated with microcystins.
• Consuming contaminated fish or shellfish (see safety precautions below).

Safety Precautions

How can you protect yourself, your family, and your pets from exposure to HABs? -

• Don't swim, water ski, or boat in areas where the water is discolored or where you see foam, scum, or mats of algae on the water.
• If you do swim in water that might have a HAB, rinse off with fresh water as soon as possible.
• Don't let pets or livestock swim in or drink from areas where the water is discolored or where you see foam, scum, or mats of algae on the water.
• If pets (especially dogs) swim in scummy water, rinse them off immediately - do not let them lick the algae (and toxins) off their fur.
• Don't irrigate lawns or golf courses with pond water that looks scummy or smells bad.
• Report any "musty" smell or taste in your drinking water to your local water utility.
• Respect any water-body closures announced by local public health authorities.
  

Is it safe for livestock to drink water with blue-green algae in it? - No. An alternative safe drinking supply must be found until the water supply is declared safe. Most livestock will prefer not to drink the water if an alternative supply is available.

Are all animals affected the same? - Most important is the amount of exposure to the toxins. Some animals are particularly sensitive. Dogs have sensitive noses and lick their fur to clean themselves, possibly taking in concentrated algae. Fish and water birds appear to be little affected. Most livestock will avoid contaminated water if possible but where they are forced to drink through scum (for example where a fence forces them to the leeward side of a dam) they may die.

Can livestock pick up toxins from irrigated pasture? - Yes. Some of the blue-green algal toxins will remain toxic in a dry form. Continued application of heavily affected waters (say from dairy waste recycling dams) can lead to significant toxin build up on foliage. Although this is a rare occurence requiring special circumstances, this residue can affect livestock.

Is blue-green algae affected water safe to drink after it has been boiled or filtered? - NO. The water needs to be filtered through activated carbon to remove any toxins. Toxins will not be removed by boiling, normal filter systems or adding household disinfectant.

Can I cook with water with blue-green algae in it? - NO. Remember boiling does not remove toxins from the water.
Can I wash clothes and dishes in water with blue-green algae in it? - Where possible use alternative water supplies. If you are unable to find another source take the following precautions:
- Use rubber gloves when handling wet washing or dishes.
- Rinse dishes with uncontaminated water
- Remove surplus water with a tea towel
- If possible give the laundry a final rinse with uncontaminated waer. Sun dry the clothes and air them for a few days.

Can I water fruit and vegetables with contaminated water? - Yes. These do not appear to take up the toxins. However, avoid fruit and vegetables coming into contact with the contaminated water. Make sure you wash the fruit or vegetables in clean water before eating.

Can I eat fish or shellfish caught in water with blue-green algae in it? - You should not eat shellfish as they can concentrate toxins. The liver and gut of fish are also likely to be toxic. Other parts of the fish may be eaten but they must be well cleaned. Further studies need to be done on the build-up of toxins in fish.

Is it safe to swim in water with blue-green algae in it? - Generally no. This will depend on the numbers and type/s of algae present. At even low levels of some blue-green algae, people and animals with sensitive skin may show some allergic reactions to the toxins present in the water. Not all people are sensitive to blue-green allergens and for those who are, the effect increases with increased exposure. The more concentrated the algae and the longer people remain in the water the more severe the symptoms.

Is it safe to boat or canoe in water where there is an algal bloom? - Safety will depend on the level of the blue-green algae. Always avoid skin contact with the water. Not all people are sensitive to Blue-green allergens and for those who are, the effect increases with increased exposure. The more concentrated the algae and the longer people remain in the water the more severe the symptoms.

Will wearing a wetsuit protect me from algal toxins? - No. In fact wetsuits may concentrate algae at the collar and cuff areas and rub cells against the skin. This may cause a particularly strong skin reaction at the points where water enters the suit. Be careful to rinse algae off the suit with fresh water if you have used it where algae concentrations are high.

Will Blue-green algae affect my irrigated crops? - Not directly in relation to toxins. The crops are not known to take up the toxins. However, Blue-green algae are fast growing and can shade and foul rice crops if they occur in bays before the crop establishes a cover above water level. This can cause significant yield loss.

Can I water fruit and vegetables with contaminated water? - Yes. These crops do not appear to take up the toxins directly. However, they should be washed well in clean water as algae may form a residue on their surface and still remain toxic even when dry.

When blue-green algae are present should I pump water from a greater depth?
- Water in deep dams may form layers of different temperature. If there is no alternative water supply, using water from areas not covered by scums, or from deeper (notably cooler) layers in dams MAY reduce algal exposure and risks.

Is the water safe once if the water no longer appears to have a bloom in it?- No. Blue-green algal cells have gas bubbles in them which affect how they float. It is common for blooms to rise to the surface in calm light conditions and sink down at other times, becoming much less evident from the bank. When cells die and break up it can take days for nerve toxins to disintegrate and weeks for liver toxins to disappear. It is best to wait a couple of weeks after a scum forming bloom has gone before using the water.

How to treat people or animals that have been exposed to cyanobacterial toxins? - Get medical treatment right away if you think you, your pet, or your livestock might have been poisoned by cyanobacterial toxins. Remove people from exposure and give them supportive treatment.

Prevention

How can I prevent an algal bloom? - Algae need three things for optimal growth: light, nutrients and high temperatures. Lowering the nutrients, light and temperature available to the blue-green algae in the water supply will help reduce algal growth. The speed at which water is flowing and mixing is important in controlling light and nutrient availability to algal cells. Keeping livestock away from the farm dam or water supply; avoiding run-off into water supply from fertilizers and pesticides; taking some water treatment measures BEFORE a bloom starts; and if practical - changing mixing patterns or covering the dam/water supply to screen out light may help.

How can I help reduce the occurrence of HABs? - Reduce nutrient loading of local ponds and lakes by using only the recommended amounts of fertilizers and pesticides on your yard. Properly maintain your household septic system. Maintain a buffer of natural vegetation around ponds and lakes to filter incoming water.

Can I use chemicals to treat water with blue-green algae in it? - Most chemicals work to PREVENT an algal bloom. Water in small dams can be protected from blue-green algae by dosing with gypsum and alum. These chemicals work by removing phosphorus from the water. Algicides can be used to safeguard water for agricultural use in farm dams BEFORE algal blooms occur. However, if used to treat a bloom, the algicide may cause a release of toxins into the water when it destroys the algae. Algicides may be toxic to organisms that naturally control algal blooms or (if not correctly applied) to livestock and humans. Before using algicides seek advice from the relevant authority.

References

CDC FAQ

Ministry of Water Land and Air Protection FAQ

MRACC FAQ

Marine Institute FAQ

MRACC ID Guide

Cyanobacterial Image Gallery (Purdue)