Some Friendly Info on Freshwater Harmful Algal Blooms (FHABs)

Jul 27, 2020 at 11:30am

State Water Resources Control Board, by Erick Burres - Citizen Monitoring Coordinator

Under certain environmental conditions in freshwater systems, single-celled bacteria, called “cyanobacteria”, can increase rapidly in biomass resulting in a “harmful algal bloom” (HAB), which in some cases can produce toxins. HABs can have negative impacts on the environment and raise serious concerns for drinking water sources, recreational use, pets, wildlife, and livestock.  

In California, toxic HABs caused by cyanobacteria (CyanoHABs) have been a recurring and escalating issue throughout the state, particularly in the Klamath River watershed, Clear Lake, Pinto Lake, Sacramento, and San Joaquin River Delta, Lake Elsinore, and East San Francisco Bay Area lakes. Additionally, Copco and Iron Gate Reservoirs, the Klamath River, and Pinto Lake was placed on the State’s 303d list due to impairment caused by cyanotoxins. In 2012, the State’s Surface Water Ambient Monitoring Program (SWAMP) sponsored a statewide workshop in response to the growing concern about cyanotoxins. The Water Boards FHABs program and the California Cyanobacteria and Harmful Algal Bloom Network (CCHAB) have responded by recreating resources for monitoring, reporting, and responding to FHABs. 



How can I report a suspicious bloom, or animal illness or human illness potentially related to a bloom? Reporting any suspected HAB or potential HAB-related illness helps authorities understand where problems are occurring and to respond appropriately. HAB coordinators can also be contacted by phone [call: 1 (916) 341-5357 or call toll free: 1 (844) 729-6466] or email ( 



Identifying a Harmful Algal Bloom 

This quick guide provides a visual comparison of appearance and color and odor that can be helpful in distinguishing non-toxic green algae and aquatic plants from potentially toxic cyanobacteria blooms or harmful algal blooms (HABs). 


Visual Guide to Observing Blooms 

This guide provides images of various algae and cyanobacteria in the field in order to help users identify and report CyanoHABs and other types of harmful algal blooms (HABs). Photographs of non-toxic algae, cyanobacteria, and other organisms of concern are provided in this guide.


SWAMP's California Freshwater Harmful Algal Bloom Field Guide 

This manual is to provide easy-to-use, individually downloadable guidance documents, forms, and standard operating procedures (SOPs) for responding to possible harmful algal blooms (HABs). The topics covered in this field guide are listed on the side of this page for easy navigation. 


CyanoHAB Guidance for Recreational Water Uses 

This voluntary guidance will assist responding organizations, including environmental and public health officials, land and waterbody managers, citizen scientists, and others in responding to inland harmful algal blooms (HABs) in California. 


California Harmful Algal Blooms (HABs) Portal: Are harmful algal blooms affecting our waters? 

The Portal is an informational resource for the public and also functions as a tool to support coordination with statewide partners to address HABs. The content is developed by the California Cyanobacteria and HAB (CCHAB) Network and participating state agencies.  

The content included here focuses on freshwater and estuarine HABs; similar content for marine (coastal) HABs is provided by the California Harmful Algal Bloom Monitoring and Alert Program (CalHABMAP) webpages