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Project: Cyanotoxins

Background and Objectives

Cyanobacteria (also called blue-green algae) are aquatic, photosynthetic bacteria. Cyanobacteria blooms can create a variety of water quality problems such as impairment to recreational uses, reduced aesthetics, lower dissolved oxygen concentrations, taste and odor problems in drinking water, and the production of toxins (called cyanotoxins). Cyanotoxins have caused wildlife mortality and are associated with liver cancer and tumors in humans. Exposure to cyanotoxins can occur by ingestion, inhalation, dermal contact, or aspiration.

Microcystins, the most commonly occurring class of cyanotoxins, last for weeks in the environment under typical ambient conditions. Their chemical stability means cyanotoxins produced in lakes, wetlands, rivers, and streams may have negative effects both locally and in downstream receiving waters, sometimes far from the site of production. As an example, since 2007, over 30 southern sea otters deaths have been attributed to microcystins in and around the Monterey Bay National Marine Sanctuary. Pinto Lake, a eutrophic lake that experiences frequent cyanobacterial blooms and drains to Monterey Bay via the Pajaro River, was identified as the primary source of the toxin. Microcystin-laden water from the Pajaro River, as well as from other tributaries to the Bay, flowed to the coast, where the toxin was biomagnified by bivalves and ultimately consumed by otters.

Cyanotoxins have recently received increased attention at both the national and state levels. A national workgroup was established in 2012, called Inland Harmful Algal Blooms (HABs), and has representatives from over 40 states that participate in regular meetings. The California Cyanobacteria Harmful Algal Blooms Network (CCHABs) was recently established in an effort to coordinate and manage harmful cyanobacteria blooms and effects in freshwater and marine ecosystems throughout California. CCHABs is a network with representatives from federal, state, and local agencies; tribes; and the regulated, academic, and nonprofit communities. While there is currently no formal statewide monitoring program, the long-term goal of CCHABs is to establish one. Voluntary statewide guidance for cyanobacteria monitoring has been established and action levels have already been determined in California in an effort to reduce the potential adverse health effects of cyanotoxins in recreational water bodies.

Because there is currently no statewide monitoring program in place for California, the immediate goal of this project is to estimate the distribution of toxigenic cyanobacteria in the state and the frequency of cyanotoxin production in wetlands, wadeable streams, estuaries, and lakes. Longer-term goals include improving understanding of cyanotoxin impacts on different types of beneficial uses, as well as the environmental drivers for cyanotoxin production in California water bodies.


This project was initiated in 2011 with anticipated completion of the first phase in 2014.


Samples are being collected in conjunction with existing monitoring efforts such as the Southern California Stormwater Monitoring Coalition (SMC), Surface Water Ambient Monitoring Program survey of depressional wetlands, and the San Diego regional reference stream study. Cyanotoxin detection relies on enzyme-linked immunosorbent assay (ELISA) and liquid chromatography-mass spectrometry (LC-MS) analyses. In San Diego depressional wetlands, Solid Phase Adsorption Toxin Tracking (SPATT) bags (a passive sampling device) were also used to screen for microcystins and determine if a more extensive analysis is warranted, thus reducing analysis costs.

Southern California sites analyzed for microcystins in 2011-2012; Note: only 12% of sites were analyzed for additional cyanotoxins beyond microcystins.


Wetlands: Half of sites sampled in spring 2012 were toxic from microcystin and 5% were toxic from saxitoxin. In San Diego, 30% of the sites were toxic based on one-time grab samples; however, the SPATT results showed 83% of sites were toxic for microcystins, indicating that one-time grab samples can miss toxic events. Most of the microcystin concentrations in 2012 were below California action levels and ranged from 0.01 to 1.7 µg/L. Saxitoxin concentrations were < 0.1 µg/L (no saxitoxin action levels are established for California). The results from 2013 showed only 13% of the sites were toxic for microcystins (none for saxitoxin) but the concentrations were very high (1.5 to 22 µg/L) and exceeded the human recreational and subchronic dog action limits (0.7 µg/L and 1.0 µg/L respectively).

Streams: Preliminary results indicate a high occurrence of potentially toxin-producing cyanobacteria, primarily benthic forms, in California streams, as well as a high level of cyanotoxin production (especially microcystins) in Southern California. A survey of nearly 1,000 wadeable streams throughout California documented at least 19 cyanobacterial genera capable of producing toxins, as well as at least six toxin-producing species. Over two-thirds of the stream reaches sampled supported at least one such genus or species. Furthermore, based on one-time sampling, 38% of sites were positive for total microcystins and 5% of sites were positive for saxitoxin. Anatoxin and lyngbyatoxin were also present but only analyzed at a subset of sites. Cyanotoxins occurred in both developed and undeveloped catchments, but were somewhat more common in developed areas.

Cyanotoxin detection (for both microcystins and saxitoxin) correlated with positive toxicity test results (Ceriodaphnia bioassays). Gaining a better understanding of local cyanotoxin impacts on stream biota could prove useful for understanding potential causes of low biotic index scores in stream bioassessment efforts. Monitoring programs involving bioassessment using benthic macroinvertebrates (BMIs) may want to consider including cyanotoxin analysis in order to account for the possibility of cyanotoxins depressing BMI index score results.

Lakes and Estuaries: A focused study of cyanotoxin prevalence in 19 San Diego area lakes and estuaries is ongoing; initial sampling revealed visible cyanobacteria blooms in two of the lakes and their riverine outflows.

Lake Henshaw in San Diego County during a July 2013 toxic cyanobacteria bloom (left); The cyanobacteria bloom was also prevalent in the riverine outflows from Lake Henshaw and positive for microcystins (right)


This project is being conducted in collaboration with the University of California, Santa Cruz; California State University, San Marcos; and San Diego and San Francisco Regional Water Quality Control Boards.


Prevalence of cyanobacteria & cyanotoxins in California water bodies - January 2013 presentation for SCCWRP member agencies introducing this research study.

For more information on Cyanotoxins, contact Betty Fetscher at (714) 755-3237 or Meredith Howard at (714) 755-3263.
This page was last updated on: 6/30/2014