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New Hampshire Department of Environmental Services

Recreational Exposure to Cyanobacteria (Blue-Green Algae)

Current Advisories
For current posted cyanobacteria beach advisories or lake warnings, check the Current Advisories page.

What You Should Know
Recent attention has been directed toward cyanobacteria Cyanobacteria in New Hampshire Waters Adobe Acrobat Reader Symbol(Fact Sheet WMB-10) in New Hampshire’s lakes and ponds. The presence of cyanobacteria in recreational waters is a great concern of the NHDES Beach Program. Blooms of these primitive cyanobacteria have caused adverse health affects, even death, in livestock, domestic animals and humans.

beach advisory for cyanobacteriaRecreational Exposure
Cyanobacteria blooms are aesthetically displeasing in sight, odor and taste, as well as potentially toxic to domestic animals, livestock, waterfowl and humans. Cyanobacteria are a potential public health danger because they may produce toxins, collectively referred to as “Cyanotoxins,” that can be released into the water when cells die or are consumed by organisms in the food chain. However, the amount of toxin produced varies over time and from lake to lake. A cyanobacteria bloom may produce very little or no toxin in one lake and a later bloom in the same lake could produce a large toxin concentration. Unfortunately, no known method exists for predicting the toxin content of a cyanobacteria bloom. These cyanotoxins target the liver, kidney, the central nervous system, and skin irritants. All cyanotoxins can cause both acute and chronic illnesses. Acute effects, such as skin and mucous membrane irritations, can occur after short term exposure with water containing these toxins. Chronic effects, such as liver, kidney, and central nervous system damage, can occur over a long period of time from water ingestion containing toxins.

Drinking Water Exposure
Although there have been confirmed blooms of cyanobacteria that are capable of producing toxins in lakes and ponds used as sources of drinking water in New Hampshire, it is not known whether cyanobacteria pose a significant threat to New Hampshire’s public water systems, other than as a source of taste and odor issues. In response to the growing concern about cyanobacteria as a threat to public health and an increase in reported bloom occurrences in New Hampshire waterways, NHDES’s Drinking Water and Groundwater Bureau now offers grants to help public water systems implement monitoring programs to monitor for potential cyanobacteria blooms. Also, NHDES’s “CyanoHAB Response Protocol for Public Water Supplies Adobe Acrobat Reader Symbol provides guidance regarding how to respond should a bloom occur within a surface waterbody used as a source of drinking water. More information is available on the Cyanobacteria and Drinking Water – Information for Public Water Systems webpage.

Common Cyanobacteria Species, Toxins and Effects

Genus Common Toxins Exposure Side-Effects
Anabaena Anatoxins (neurotoxin), Microcystins (hepatotoxin) Swimming (skin contact and swallowing water), showering (if drawing water from lake), water sports, boating Nausea, vomiting, diarrhea, general malaise, severe thirst, skin and mucous membrane irritation, staggering, and paralysis
Aphanizomenon Saxitoxins (neurotoxin) Swimming (skin contact and swallowing water), showering (if drawing water from lake), water sports, boating Numbness of lips and mouth extending throughout the body, motor weakness, respiratory and muscular paralysis
Microcystis Microcystins Swimming (skin contact and swallowing water), showering (if drawing water from lake), water sports, boating Nausea, vomiting, diarrhea, general malaise, severe thirst, skin and mucous membrane irritation
Oscillatoria Anatoxins, Microcystins, Aplysiatoxins (dermatotoxin) Swimming (skin contact and swallowing water), showering (if drawing water from lake), water sports, boating Nausea, vomiting, diarrhea, general malaise, skin and mucous membrane irritation

The Beach Program takes a proactive approach when cyanobacteria blooms or scums appear at public beaches. A beach advisory is posted when a potentially toxic cyanobacteria species is present and identified as the dominant algae in the cell count.

You may use the tell-tale signs of cyanobacteria to initially identify its presence in the water, described in the Ecology section below. However, cyanobacteria may only be positively identified to the Genus level by microscopic identification. If you suspect a cyanobacteria bloom is occurring at your lake or pond, please call NHDES immediately at (603) 848-8094 (Beaches/Cyanobacteria Hotline), or (603) 271-0698 (office of A. McQuaid), or and we will conduct a site visit. You may also collect a sample in a clean container (plastic or glass jar) and bring it to NHDES (link to directions to NHDES) to identify. Caution: If collecting a potentially toxic algal sample, avoid contact with skin. Wear water-proof gloves when sampling and/or immediately wash all areas of the body where water contact has occurred.

The University of New Hampshire is currently conducting research on cyanobacteria species in New Hampshire lakes, streams, and the Great Bay Estuary. Research is also being conducted by the Dartmouth  Hitchcock Medical Center on a possible link between cyanotoxins and ALS (Lou Gehrig’s disease)
Links to cyanobacteria related information

You can help keep the cyanobacteria from forming in the first place. Research indicates that their numbers increase as the nutrients in the water increase. To reduce the chances of a bloom occurring, reduce the amount of nutrients, such as phosphates, that enter the water. Homeowners can help by testing their soils before applying fertilizers and, if they must apply a fertilizer, making sure that they apply only what they need. The NH Shoreland Protection Act prohibits the use of fertilizer closer than 25 feet from shore. Also, between 25 and 250 feet from shore, only low phosphate, slow release nitrogen fertilizer may be used. Keeping your septic system maintained will also help keep nutrients from leaching through the soil into nearby streams or lakes.

What exactly are cyanobacteria? Cyanobacteria are photosynthetic, single-celled organisms lacking nuclear membranes, and many are capable of converting nitrogen to usable forms. Some species have resting cells that are dormant when conditions are unfavorable for cell reproduction. The cells remain dormant, normally in lake sediment, until optimum conditions exist to initiate cell reproduction. Cyanobacteria are present in virtually all natural environments including many extreme environments, such as hot springs and glacial ice.

Cyanobacteria commonly occur in nearly all of New Hampshire’s waterways. When present in low numbers they do not cause recreational or aesthetic problems; however, when conditions are optimal, they may form blooms. Factors contributing to blooms include nutrient availability, sunlight and temperature.

Cyanobacteria tend to colonize mesotrophic (moderately productive) or eutrophic Adobe Acrobat Reader Symbol(Fact Sheet BB-3) (highly productive) water bodies, meaning they thrive in nutrient rich waters. Along with nutrient rich conditions they require ample amounts of sunlight to photosynthesize. In order to maximize their potential for photosynthesis, cyanobacteria are unique in that they contain gas vesicles. These vesicles allow cyanobacteria to regulate their buoyancy and depth in the water column, allowing them to out-compete algal species for sunlight. As well as nutrients and sunlight, cyanobacteria seem to thrive in warmer water temperatures and calm (stagnant) conditions for optimal growth. That’s why we typically see cyanobacteria during the summer months, especially August, when there is an abundance of sunlight and water temperatures are the warmest.

Cyanobacteria are also less susceptible to predation, compared to other algal species, and often form colonies or filaments too large for zooplankton to eat. The lack of predation and their competitive nature combined with optimal nutrient concentrations may cause bloom conditions. A cyanobacteria bloom may turn the water a bright green (pea-soup) or bluish-green color and/or produce septic or grassy odor. Cyanobacteria can appear in the form of a scum or film on the surface of the water. A bloom may have the appearance of spilled paint on the water’s surface, car antifreeze, or bluish green chunks floating throughout the water column. A bloom may cover an entire water body or be confined to a cove area and often congregates along the windward shoreline from wind and wave action. See the images at the bottom of this page for examples of blooms.

Cyanobacteria are present in many different forms. Cyanobacteria may form filaments, colonies, or be single celled. Cells vary in size from less than 1 micrometer (µm) in diameter to greater than 20 µm in length. Some colonies made up of single cells may reach greater than 100 µm in diameter. Some colonies or filaments form irregular shapes; while others produce mucilaginous sheaths surrounding the cells.
Cyanobacteria also produce two specialized cell types:

  • Resting cells or akinetes. Akinetes may be released by vegetative cells or attached to filaments. The cells function as an asexual resting state capable of resisting harsh environmental conditions (winter) and can germinate to form new filaments when conditions improve.
Nitrogen fixers or heterocysts. Heterocysts are gas tight and anaerobic, and contain the nitrogenase enzyme. This enzyme enables the cell to convert gaseous nitrogen (N2), from the atmosphere or dissolved in water, into ammonium (NH4+).

Images of Cyanobacteria Blooms

Bow Lake, Northwood
Bow Lake, Northwood, NH (2006)
  Baboosic Lake, Amherst
Baboosic Lake, Amherst, NH (2006)
Lake Monomonac, Rindge
Lake Monomonac, Rindge, NH (2006)
  Webster Lake, Franklin
Webster Lake, Franklin (2005)
Baboosic Lake, Amherst
Baboosic Lake, Amherst, NH
  Oscillatoria bloom
Oscillatoria bloom

NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

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