Harmful Algal Blooms (HABs)

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HAB Basics

HABs are occurring more frequently around Utah in response to increased nutrients in waterbodies and a warmer climate. Harmful algae (cyanobacteria or blue-green algae) naturally grow in waterbodies driven by water temperature and nutrient availability. Cyanobacteria produce toxins that can be dangerous and impact humans, pets and livestock, aquatic life, and agricultural irrigation. It is important to learn how to identify a HAB to help keep yourself and others safe.

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Introduction to Harmful Algal Blooms

A harmful algal bloom is a phytoplankton containing toxic cyanobacteria. Often referred to as HABs, cyanobacteria occur when the concentration of nutrients, temperature, and turbulence in a body of water is just right to promote algal growth.

Identifying Common HABs

To begin identifying algae types, make sure the suspected bloom is not filamentous green algae or duckweed, two common and harmless aquatic plants. If it is not a harmless aquatic plant, then it may be one of the following common HAB types.

General InformationFilamentous AlgaeDuckweedCommon HABs

Harmful algal blooms (HABs) are large growths of cyanobacteria that may change the water color or form surface scums and occur in lakes, reservoirs, ponds, and less frequently in streams. Cyanobacteria can produce deadly toxins that are harmful to human, livestock, and pet health. These tiny plant-like bacteria produce toxins that can attack the kidneys, liver, reproductive and nervous systems, and irritate the skin. Animals and swimmers, which often ingest surface waters, are at particular risk.

Cyanobacteria blooms tend to take two forms:

1. HABs can be suspended throughout the water column. Blooms forming in the water column can look like “pea soup,” green clumps or globules, green mats, or grass clippings.
2. HABs can form a thick surface scum. These scums develop when the cyanobacteria begin to die and cannot control their buoyancy. These scums can be especially toxic. These HABs are often described as looking like “spilled paint” or streaks on the water surface and may change color (green, white, blue, red, purple, brown) over time.

Green algae come in many forms and may look like underwater moss, thick stringy mats, or floating slimy scum. Types of green algae can look a lot like cyanobacteria and grow in similar nutrient-enriched waterbodies. Unlike cyanobacteria, green algae may form long filamentous strands that make up silky “clouds” below the surface or viscous mats on the surface.

The stick test:
Find a sturdy stick or pole and pull it through the algae. If the stick pulls out strands that look like green hair or threads, the mat on the pond is likely filamentous green algae (non-toxic). If not, you may have a harmful algal bloom.

Duckweed are tiny aquatic plants with a grainy or couscous-like texture that can cover the entire surface of calm, nutrient-enriched ponds. They may resemble miniature lily pads and are generally beneficial to the environment. If you collect them using a stick, you will notice their tiny leaves and root structures.

Before entering a waterbody, check the area for HABs (see examples of different HAB types below). It can be difficult to identify the type, so do not worry if you do not know exactly what type of HAB you are seeing. The important thing to remember is if you suspect a HAB is present, do not get in the water or allow children, pets, or livestock to enter or drink the water.

If you think a HAB is present, you can contact the 24-hour Environmental Incidents Line at (801) 536-4123 to notify the Utah Division of Water Quality (DWQ). They will determine if water testing and public health watches are necessary for the waterbody.

You can check the DWQ Recreational Water Monitoring Map to see which monitored waterbodies are currently experiencing health concerns (E. coli and HABs). This is a great practice to do before heading out to a waterbody during the summer.

Photos examples courtesy of DWQ More examples can be found on their website here.

Type of Algae	Picture
Spilled Paint HABs
Clump or Glob HABs
Pea Soup HABs
Green Mat HABs
Grass Clipping HABs
Bright Green HABs
Blue-Green Residue HABs
Benthic HABs