Algae Monitoring

Eel River residents and UC Berkeley combine efforts

The Eel River Recovery Project has been working with the University of California Berkley (UCB) to monitor toxic cyanobacteria, commonly known as blue-green algae. Most algae are non-toxic and are an essential part of the food web (see All About Algae page).

Historically, the Eel River was cold and low in nutrients, but recent developments within the watershed have lead to algae blooms that have proven toxic to dogs. Annual cycles of algae growth vary with flow and temperature, and problems may be minimal in wet years. Watershed residents expressed alarm that the Eel River had become unsafe during early ERRP meetings and then they stepped forward to help monitor to determine the extent and cause of this new problem. Toxic Algae Fact Sheet.

ERRP has helped monitor Cyanotoxins throughout the Eel River basin since 2013 in partnership with UC Berkeley (See report).  Doctoral candidate Keith Bouma-Gregson has taken the lead in the project. See more details, below.
The 2015 results for presence/absence of cyanotoxins at 14 stations show that 77 % tested positive for Anatoxin-A, which has the ability to produce neurotoxins. Ambient levels are not high enough to pose a high health risk at present. The danger is pets and people, especially small children, coming in direct contact with blooms. The highest monthly levels of toxins were measured at Myers Flat, below Sproul Creek, and above Scotia, respectively

The study, also found that:  

• Toxic algae blooms and measured cyanotoxins are highest on the South Fork Eel River from Myers Flat upstream to Leggett.
• Cyanotoxin production peaks in late July and early August.
• Anatoxin-a is a neurotoxin and most common in the Eel River, while liver toxin microcystin is present but only at very low levels.
• The most common types of toxic blue-green algae in the Eel River are Anabaena and Phormidium, with Nostoc also potentially supplying a lesser amount.
• Anabaena tends to form mats on the edges of the river and creates an attractive nuisance for dogs, while Phormidium grows in riffles where contact is less likely.

On February 24, 2016 Regional Water Board staff hosted a public workshop to discuss monitoring, assessment and response strategies for freshwater Cyanobacteria harmful algal blooms (cyanoHABs), and provide information on the prevalence and effects of cyanoHABs. The agenda for the workshop and all presentations are available here.  Read Keith Bouma-Gregson's report to the Water Board about cyanoHABS in the Eel River.

The Thirsty Eel:  Summer and Winter Flow Thresholds that Tilt the Eel River of Northwestern California from Salmon-Supporting to Cyanobacterially-Degraded States.  For Special Volume, Copeia: Fish out of Water Symposium.

Sampling Methods

Solid phase adsorptive toxin tracking (SPATT) samplers placed at various Eel River locations catch cyanotoxin molecules. The concentrations of cyanotoxins allow comparison between sites and years, but do not provide quantitative data that can be compared to public health thresholds. In 2013 and 2014 SPATTs were rotated weekly. In 2015, they were placed for monthly intervals at an expanded number of locations. Automated water temperature probes are also deployed with SPATTs to test for associations between elevated temperatures and algae blooms. UC Santa Cruz is helping by processing the SPATTs.

UCB is Helping the Eel River Community

ERRP is grateful for the continued support of UC Berkeley, which goes beyond the needs of Bouma-Gregson’s doctoral studies.  For instance, UCB assisted the Humboldt County Sheriffs Department in July 2015 by teaching them to identify potentially toxic algae to ensure the safety of cadaver sniffing dogs that searched the river.

Funding for UCB research is being provided in part by a U.S. EPA STAR Fellowship and the National Science Foundation Critical Zone Observatory grant.

Types of Eel River Toxic Cyanobacteria

Anabaena in algae mats

This is the edge water at Phillipsville where dog mortality occurred in 2009.  Floating algae mats likely contain decaying fragments of toxic Anabaena. This cyanobacteria likes warm stream margins and tends to colonize decaying green algae beds as flows drop. Not all cyanobacteria cells produce toxins, and toxins may not be normally released from cells. However, as cells break down or when cells are broken open, toxins may be released.

Anabaena in algae spires

Darker colored Anabaena spires colonize decaying green algae at Phillipsville on the South Fork Eel River. It forms gelatinous masses around the decaying algae that trap oxygen during diurnal photosynthesis and create pencil like spires that are dark green or even blue-green in color. Segments of the spires may slough off and create mats that pose major risk to dogs and children.


Phormidium forms durable mats on cobble, boulders or bedrock in rapids or riffles that range from tan to dark brown in color and may have a velvety or feathery appearance. These mats are capable of producing anatoxin-a, but they present less health risk to pets and people because they grow submerged in riffles. Lack of visible Anabaena mats in the reach of the South Fork Eel at Leggett suggests that Phormidium may be a contributor to elevated levels of cyanotoxins there.


This cyanobacteria species forms brown, beige or blue-green durable gelatinous balls that grow most often in riffles, but sometimes also in shallow pools. Shape of Nostoc may vary to include ear-shaped and blade forms of growth. UCB sampling within patches of Nostoc found some cyanotoxins, but lesser levels than in Anabaena and Phormidium. Similar to the latter, Nostoc tends not to slough off and form mats.

UCB and ERRP Expand Cyanotoxin Monitoring in 2015

Partnership with Round Valley Tribes
ERRP is very pleased for the opportunity to assist the RVIT in monitoring waters of the Reservation and nearby tributaries of the Middle Fork and North Fork Eel River.

The RVIT Environmental Protection Agency staff are benefiting from the cooperative monitoring with ERRP and UCB and hope to build capacity for long term trend monitoring. RVIT EPA also has a strong working relationship with North Coast Regional Board staff that helps them identify pollutants and devise monitoring plans needed to protect beneficial uses of water on the Reservation.

ERRP received a State Water Resources Control Board grant in 2015 to work with small water districts and the Round Valley Indian Tribes to expand cyanotoxin monitoring locations.

Findings from 2013-2014 suggested that only the South Fork Eel River and upper Van Duzen are currently susceptible to toxin cyanobacteria, but more samples were needed on the main Eel River and in major tributaries like the Middle Fork. ERRP also placed SPATTs upstream of water intakes for the Alderpoint and Redway water districts and the lower Eel River at Scotia to supply information to the Scotia Community Services District that is considering options for a river park.


ERRP’s Bruce Hillbach-Barger (center) with Round Valley Indian Tribe's EPA technicians in the field to deploy a SPATT on the Middle Fork Eel just upstream of the Reservation.

Listen to an interview with biologist and Berkeley professor, Dr. Mary Power.  She talks about how reduced flow causes the river to produce more potentially toxic blue-green algae.