Idaho DEQ Cyanobacteria Harmful Algal Bloom Information

There are three ways to report a potential cyanobacteria harmful algal bloom (HAB):

• Use the   Report A Environmental Concern  form. Please add photos of the water. Photos are really useful for pre-screening potential blooms.
• Email algae@deq.idaho.gov with a description of the potential bloom. Please include the water body's name, the location of the bloom on the waterbody, and attach photographs. A close-up photograph of the bloom, as well as a wide shot showing the extent of the bloom is helpful.
• Call the DEQ HABs Hotline at 1-866-671-5385.

Please see below for tips on correctly identifying HABs.

The physical appearance of these blooms can be unsightly, often presenting as discolored water, streaks or globs of scum, and/or thick green mats or scum along lake shorelines. The blooms can vary in color. For example, they can appear as a split-pea soup, iridescent green paint, or brown. The pictures below may help in correctly identifying HABs. The USGS has also published a field guide for identifying HABs, which can be accessed  here .

What about other types of algae? Algae in our lakes, ponds, and streams are an essential component of the food web and a healthy aquatic ecosystem. Algae have many forms and colors, and most do not produce toxins. Cyanobacteria (blue-green algae) are the exception.

These infographics from the California State Water Resources Control Board are useful for distinguishing between non-HABs (left) and HABs (right). If you see what you believe is a HAB, stay out of the water and report it using the resources above. You may also perform a simple stick or jar test-  click here for more information .

DEQ staff use several techniques to monitor harmful cyanobacteria in Idaho water bodies. These techniques allow DEQ to identify potential blooms before they begin and estimate a bloom’s cyanobacteria population density. Satellite (remote sensing) technologies allows DEQ staff to remotely monitor water bodies for the following purposes:

• to identify water bodies that may be in the early stages of bloom development,
• to monitor a bloom’s density once high toxin levels are confirmed,
• to determine when toxin concentrations may have returned to safe levels.

DEQ and the Idaho public health districts rely on boaters, fishermen, and anyone who visits Idaho's lakes to let us know when they see a potential bloom, there are simply too many lakes and reservoirs for us to actively monitor. Please email photos, descriptions, and location information to algae@deq.idaho.gov.

• DEQ staff will visit the water body, typically within 1-2 days,
• They will make a visual observation (is a potential bloom visible and how large an area does it cover),
• If it looks like a HAB, staff will collect a sample to see to determine if toxins are present in harmful concentrations.

DEQ uses multiple methods to measure the levels of cyanotoxins and cyanobacteria in surface water. The figure below is an example of the different sampling approaches DEQ takes based on the type of waterbody, and the location of the bloom.

DEQ and the Idaho public health districts work together to issue a health advisory. A health advisory informs the public of where an active, potentially toxic bloom has been confirmed. DEQ staff typically respond to reported blooms by visiting the water body, collecting samples, identifying the potential toxin-producing species, and analyzing the sample for toxins. The public health districts use the sample data and DEQ observations to issue a health advisory. Health advisories are lifted once toxin levels are below the safe threshold. According to the response plan, DEQ has to have two samples below threshold at least one week apart for DHW to lift the advisory

The Department of Health and Welfare Recreational Water Health Advisories and Map can be accessed   here  .

No surface water quality criteria exist for cyanobacteria harmful algal blooms in Idaho at present. However, DEQ utilizes the 2019 EPA updated recommendation for human health recreational criteria thresholds for microcystins and cylindrospermopsin (See Table below). In the following section and in additional resources, you can find out more about cyanotoxins and cyanobacteria.

Cyanobacteria (also referred to as blue-green algae) are photosynthetic bacteria that are ubiquitous in nature and are found in surface waters. Environmental conditions can promote excessive growth of cyanobacteria which can lead to high cyanobacterial cell density, known as blooms. Some cyanobacteria, but not all, have the ability to produce toxins known as cyanotoxins. The abundance of toxin-producing cyanobacteria can vary within the overall cyanobacteria population, from waterbody to waterbody, and over time within a single waterbody.

DEQ tests for both the number of cyanobacteria present in a sample of water (cell density) and cyanotoxin levels. Exposure to cyanotoxins can cause health effects ranging from mild skin irritation and upset stomach to more serious effects including trouble breathing or even death. Anyone with symptoms should seek medical attention. Cyanotoxins can also be particularly harmful to dogs and other animals that may swim in the water. While studies on the health outcomes of human exposure to high densities of cyanobacteria cells are inconclusive, some studies have shown adverse inflammatory health effects. Cell density advisories are an additional measure that can protect against exposure to high densities of potentially toxic-producing cyanobacteria.

DEQ follows thresholds as recommended by EPA for two types of cyanotoxins, Microcystins and Cylindrospermopsin. Since Microcystis is a genus of cyanobacteria that is known to be a high producer of cyanotoxins, DEQ also follows a cell density threshold for that group of cyanobacteria.

Microcystins are a type of cyanotoxin that can be produced by a variety of toxic-producing cyanobacteria genera, including Microcystis, Anabaena, Dolichospermum, Nostoc, Oscillatoria, Fischerella, Planktothrix, and Gloeotrichia. Some of these species can be distributed through the water column, concentrate in the upper layers, or form surface scum depending on environmental conditions. Microcystins typically have a half-life of four to 14 days in surface waters or may persist longer, depending on factors such as photodegradation, bacteria, and the presence of organic matter. Microcystins can persist even after a toxic cyanobacterial bloom is no longer visible.

Cylindrospermopsin is a cyanotoxin that can be produced by a variety of toxic-producing cyanobacteria species, including Cylindrospermopsis raciborskii, Aphanizomenon, Anabaena, Lyngbya wollei, and Raphidiopsis. Some of these species tend not to form visible surface scums, and the highest concentrations of total cyanobacterial cells typically occur below the water surface. The biodegradation of cylindrospermopsin in natural water bodies is a complex process that can be influenced by many environmental factors, including toxin concentration, water temperature, sunlight, and the presence of other bacteria. Half-lives of 11 to 15 days and up to eight weeks have been reported for cylindrospermopsin in surface waters.

  CDC Harmful Algal Blooms Homepage  

 USDA NRCS How to Protect Livestock from Harmful Algal Blooms 

  Idaho Department of Health and Welfare Cyanobacterial Blooms FAQ  

  Idaho Department of Health and Welfare Recreational Waters Homepage   (including water health advisories)

  ITRC HCB Visual Identification Guide  

  ITRC HCB Webpage  

  ITRC Benthic HCB Webpage  

  USGS Freshwater HABs Field Identification Guide  

  EPA Cyanobacterial Harmful Algal Blooms in Waterbodies   

  California Water Board HABs Identification Guide  

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