Eel River Recovery Project Publishes Five Year Summary of Toxic Algae Findings (2013-2017)

This is a press release from the Eel River Recovery Project:

The Eel River Recovery Project (ERRP) is grassroots group that works with volunteers throughout the watershed to collect scientific data to improve community understanding of the status and trends of river health and fish populations. The group is publishing a report entitled Eel River Cooperative Cyanotoxin Analysis Summary 2013-2017 that discusses the sources of algal toxins, the geographic extent of the problem, and factors that may be stimulating noxious blooms. This study is one of the first in the Western United States to look at cyanotoxin development in a river system, while blooms in lakes and reservoirs are better studied.

Cooperators in the study include the University of California Berkeley (UCB), UC Santa Cruz, and the North Coast Regional Water Quality Control Board (NCRWQCB). Studies were initiated in 2013 under the direction of UCB doctoral candidate Keith Bouma-Gregson who worked with volunteers and set up the study design for assessing toxic cyanobacteria on a basinwide scale. Data were collected weekly in 2013 and 2014 as a basis for Keith’s doctoral dissertation. In 2015-2017, data were collected monthly during summer months.  A total of 332 cyanotoxin sampling devices were deployed at 20 locations throughout the Eel River watershed from 2013 to 2017.

Results indicated widespread occurrence of two types of toxins produced by cyanobacteria: anatoxin-a and microcystin. Dog deaths documented since 2001 were as a result of exposure to anatoxin-a, which is a fast-acting neurotoxin. Microcystin attacks the liver and is a significant problem in the nearby Klamath River, but it occurs at only very low levels in the Eel River basin and has little potential impact on public health presently.

Anabaena on South Fork at Phillipsville. Notes oxygen bubbles trapped in colonies that cause segments to float and drift.

The cyanobacteria Anabaena, the greatest source of anatoxin-a, thrives in warm water, particularly in stagnant water at channel margins. This colonial organism forms on dead and dying Cladophora, the beneficial green algae that fuels the aquatic food chain. Anabaena creates dark green spires that have embedded oxygen bubbles created during photosynthesis. Segments tend to become buoyant in the afternoon and can be loosened by wind and float downstream to form scums and floating mats. When dogs roll in patches of Anabaena or frolic through scums and then lick their fur, they are exposed to a lethal dose of neurotoxins.

The South Fork Eel River had the highest levels of anatoxin-a in most years. In 2013, the highest levels were in the lower reach at Phillipsville; in 2014, the highest levels were measured farther upstream, near Piercy. The pattern changed in 2015, when the highest anatoxin-a levels were measured in the lower Middle Fork, upper Eel, the lower Eel River, and the Van Duzen River near Carlotta, as well as in the South Fork.

Very low flows and high air temperatures in spring of 2015 gave blooms an early start and there were no flushing flows until November. Extremely low late summer flows may also have allowed Anabaena colonization across the entire river bed, as opposed to just in the edges of the stream. The high flow years of 2016 and 2017 had much lower levels of cyanotoxins basinwide.

Although Middle Fork and upper main Eel River locations had higher water temperatures than the South Fork, they rarely had high levels of cyanotoxins. This suggests factors other than water temperature are driving blooms and nutrient pollution is suspected. Summer base flow of the South Fork Eel River has declined from historic levels based on U.S. Geologic Survey data, and this promotes warming and nutrient concentration. This pushes the river past a tipping point from a cold-water/green algae dominated ecosystem to a warm water/cyanobacteria dominated one.

The report acknowledges that direct water diversion plays a role in diminished base flows, but points out that perturbed watershed hydrology may be of equal or greater import. Forests in the Eel River watershed were profoundly altered by post WWII logging. Stands of old growth trees spaced far apart were replaced with dense forests of mixed conifers and hardwoods that use much more water due to increased evapotranspiration. High road densities, another legacy of logging, increase winter peak flows and diminish percolation into the landscape. These two factors effects are likely contributing to decreased summer flows.

In 2016 a dog died along the upper Eel River within the Potter Valley Project at Trout Creek of apparent exposure to cyanotoxins. Lush growth of another anatoxin-a producing species, Phormidium, was found nearby and was the likely source of the toxins. This species prefers fast-moving riffles and can tolerate cold water. It is well studied in New Zealand, where it causes widespread livestock mortality. Further study is needed to understand more about what is causing Phormidium blooms and what level of public health risk they pose in the upper Eel River.

Phormidium mats near Trout Creek on upper Eel River within the Potter Valley Project. Photo courtesy of Rich Fadness, NCRWQCB. 9/15/16.

Eel River below South Fork convergence at Dyerville looking upstream. 8/24/18

ERRP is once again conducting basin wide cyanotoxin and water temperature monitoring in 2018. Low flows are causing significant late summer algae blooms, similar to 2015. Aquatic recreation is not recommended at present on the lower South Fork or lower main Eel River.

Because there is no dedicated funding for cyanotoxin research, ERRP is conducting a fundraising drive to get public support for this important work. Donations can be mailed to ERRP, P.O. Box 214, Loleta, CA 95551 or made on-line at

In addition to the new report, the website has links to Keith Bouma-Gregson’s doctoral dissertation and three related peer reviewed publications. His work and UCB involvement were made possible by an Environmental Protection Agency STAR Fellowship and the National Science Foundation Eel River Critical Zone Observatory grant. Call 707 223-7200 if you want to volunteer or to request monitoring of the river reach or creek near you.

Map of locations of cyanotoxin samplers (SPATTs) placed in the Eel River basin from 2013-2017.



  • Out of curiosity, I wonder how much grant money was spent on the study?

    “nutrient pollution is suspected” looking at the estuaries of almost all the major rivers in America, you can see the algae blooms caused by industrial fertilizer runoff, it’s crazy. It’s gotten so bad that major rivers like the Mississippi have actually developed a “dead zone” running up the river and out into the ocean.

  • Lucky for the “medicine” industry they have legacy of logging to blame for this shit show…First it was the canneries,then it was the dams, then it was the loggers, then it was the vintners, then it was the squawfish. The tens of thousands of years of genera of salmonids were windmilling on top of the fence when the grweed industry shoved them over for the last and final time. Last I checked, fish need clean, cool water to survive… Reap it…

  • Everybody thinks organic fertilizer will solve these problems too. If i had a dollar for every time i heard “but i use organic!” WeLl It StILl GOeS InTo ThE RiVeR aNd FeEdS ThE AlGaE gRoWTh

    • As long as people can spend money on commercial fertilizer and reap a profit from irresponsible use, they will continue to apply way in excess of what produces good growth.

      But most organic at least builds soil, which is less likely to runoff. Bugs and microorganisms like to eat it before it gets too far down hill.

  • Everyone has an opinion but doesn’t know shit! I’m in the river every year fishing for steelhead. Holes that WERE well known to be deep and cold and full of steelhead are completely silted in. Used to be bottomless are now shallow enough to walk across in March. The water is there, it’s just under the silt. Major land slides along the river along with poor property development create mud flows that fill the river. Ask someone who’s in the river, not driving by it. Confusion Hill slide dumps tons of mud in the river every winter. Thus making the river shallow and warm. Get off your ass and make a difference before making a comment.

    • And over the last 40 years there are thousand up thousands of miles of new dirt roads in the county. Where the dust is a foot deep. All going into the rivers and silting in what used to be gravel spawning grounds.

    • Isn’t that a reversal of physics? Last time I checked, dirt/mud is heavier than water and will sink to the bottom. When thes space in these fish holes that are claimed to have been filled in, the water level will actually rise.
      But for entertainment’s sake, if ther dirt/mud was lighter than water, then wouldn’t it be all taken out to sea, even in low flowing times?
      And the explanation that the water is being driven underground is just plain stupid. Any normal person can reason that the amount of rock that would need to be displaced from under the soil for the surface water to all but disappear in the summer months would take million of years. Not just 40 years.
      The entire problem is the Potter Valley Project. Plain and simple. Take the water away from the Eel, and get exactly what we’re getting now. Stop the damming of the Eel River!

      • The Eel river water diverted to Potter Valley is water saved from Winter’s rain. The only affect from the dams on the Eel is slightly warmer water getting released and and higher rate of flow than naturally. Well that and the blockage of spawning areas by the dam

        • A higher rate of flow to the Russian River.

          • Nope, the flow of the Eel is increased during the summer months due to the dam. Don’t believe me? Google it and read up

            • The best explanation of the dam releases I’ve found is on page 56 here:
              I do believe LTL is correct that the summer releases are generally a little higher than the natural flows

              • Nope, those are not the “natural” flows. They are greatly altered by post invasion vegetation alteration, road building and micro and macro climate changes. They were previously altered by native land management practices, particularly human fire use (perhaps less in that part of the landscape because Yuki people may have used far less intentional fire than most other native people).

                Slaughter of the native managed grazing and browsing herds as well as of the predator populations accompanied by european grazing animals en masse converted landscapes from soil holding, water and carbon sequestering bunch grasses to european annuals which are adapted to climates with regular summer rains and actively desiccate soils to ensure dry seeds. Logging of old growth forests reduced the water holding capacities of soils especially in uplands and riparian zones. Road building cut through top soils lowering soil moisture horizons and water tables both above and below the roads. Planting of even aged Doug Fir plantations in areas at the dry limit of Doug Fir’s natural range led to more transpiration of soil and ground water reducing stream flow. Some sources say that open oak woodlands shaded summer soils reducing evaporation; their reduction probably decreased stream flows. Removal of salmon runs reduced phosphorous and nitrogen return to the soils. Alteration of the coastal forests (major reductions of mature Redwood and Tanoak groves) reduced inland humidity and (especially) summer rains.

                Fire suppression which leaves heavy brush, and fire suppression practices (dozer lines and uphill backburns) have also greatly altered landscapes and likely result in less consistent water flow.

                Of course cannabis cultivation and everybody’s roads (including the growers’ roads) have greatly altered the landscape in the rest of the Eel. The attempts to control cannabis via asset forfeiture drove cultivation onto public lands but without additional roads. Cannabis has been a big additional factor in the South Fork but relatively minor (though incredibly intrusive and ugly) in the upper mainstem above the Pillsbury Dam

  • And over the last 40 years there are thousand up thousands of miles of new dirt roads in the county. Where the dust is a foot deep. All going into the rivers and silting in what used to be gravel spawning grounds.

  • Over 30 years guiding all stems of the Eel, in a driftboat and an inflatable cat. That makes me the expert, I guess… Now, you get off your ass…

  • “The report acknowledges that direct water diversion plays a role in diminished base flows, but points out that perturbed watershed hydrology may be of equal or greater import. Forests in the Eel River watershed were profoundly altered by post WWII logging. Stands of old growth trees spaced far apart were replaced with dense forests of mixed conifers and hardwoods that use much more water due to increased evapotranspiration. High road densities, another legacy of logging, increase winter peak flows and diminish percolation into the landscape. These two factors effects are likely contributing to decreased summer flows.”

    Do you have the data for this hypothesis, i.e. what is the percentage of direct human water diversion from the Eel River watershed vs the two other examples you give?

    I have heard other people within the cannabis industry use this same claim, but no one can tell me what they are quoting from. They use this same hypothesis when defending marijuana grows. Does ERRP have documentation, reports, studies or specific scientific facts to back up your claim?

    Can you also explain who or what will benefit from this study, e.g. Eel River Cooperative Cyanotoxin Analysis Summary 2013-2017?

    Has the Cannabis Industry or Festival promoters ever sponsored or provided funding/grants to ERRP’s efforts or specific study ERRP has benefited from?

  • Southpaw, you nailed it. Right you are, sir. Wanna float the main? We can document the travesty mile by mile. Seems like you are on the same page as me. Be well.

    • The river changes, Fernbridge hole is almost completely filled in with gravel while Weymouth is now down to solid.

      The tribs getting sucked dry is the Eel’s biggest prob.

  • Sue humboldt county

    Potter valley deversion it is, all this other blaim game of the people down stream is a smokescreen for extortion and theivery.remember when voting in november its time for new representation for northern ca.the current regime definitely doesn’t have the majority in its best intrest.tear down the damm and the deversion and lets see how the river fairs and heals!!!!!

  • Ltl, The reasons you mention are valid. with the exception of the term “slightly” (your term, not mine) not to fling poo, but the pvp and Scott dam have been killing the river since their installation. The fix, please… Again, not to yawn your observation by any means. The “Steal from the Eel” diversion was another nail in the coffin. When does any rain in that (Eel) watershed fall, but winter?

    • How don’t you understand what I posted? There is zero water “stolen” from the Eel. The water that is diverted to Potter Valley is winter’s rain. That water, if not captured in the reservoirs, it would run right out into the Pacific ocean

  • Exactly! Where it should go in the first place… Zero water stolen? [edit] ZERO? Holy fuck’s sake! IT IS or WAS Eel river water in the first place) How goddamn dare you to minimize the pvp rape… [edit]… The mention of the word “diversion’ [edit] lets everyone reading your [edit] post know what side of the fence you are on!

    • I’m not on a “side” … I’m for the truth. If we keep blaming the state of OUR river on the PVP … nothing will change.

      Honestly, I think the best case scenario would be if the stake holders on the Eel could work a deal with the stake holders on the Russian. A deal which would give the Eel more flow in the early summer when juvenile fish are trying to make their way down stream.

  • Let the Russian river die, except that it died about 25 years ago! Long live the mighty Eel! Fuck the silage/cattle barons in Potter valley, (pot barons included) Don’t blame me, or any other Eel river lover for the defense of MY (our) home river! I hope it floods bigtime this winter, it might just wash the parasites into the ocean. When the damns (sic) come down, the playing field will level…

    • Full disclosure and just to set the record straight; its the East Fork of the Russian River and the headwaters of the Eel River start in Mendocino County, flows into Lake Pillsbury in lake County, flows back through Mendocino County by approx 90 miles before it enters Humboldt County. Don’t get me wrong, I advocate for free flowing streams and the Wild & Scenic Rivers Act. However, I do not consider any river my or our river. We need to get past this. It’s not our river! And it needs to be free flowing all the way to the Pacific, just like the South Fork without Benbow Damn…

  • Have any of the test sites reported dangerous levels this year?

  • Hold on Ed, you forgot to disclose the FACT that “the” river (Main stem) gets chopped in half at P.V.P. at the time of the year when 1-2 year old salmonids need it most, in the early summer, to late fall until rains come. This rape has effected the health of the Eel since it’s inception. The ONLY reason the Russian River exists after about the first of July is the Eel that has been diverted through the P.V.P. Wanna call B.S? Shunt the Eel from the Russian next year, and have a nice walk down a dry gravel ditch that used to be the “Mighty Russian”…

  • Only 1% of the water from the eel is diverted to the Russian.

    • According to Wikipedia, “Reduction in flow occurs in part due to deliberate water diversion from the Eel to the Russian River watershed by the Pacific Gas and Electric Company’s Potter Valley Project, located to the south in Mendocino County. Although the effect on the total annual flow is negligible (only about 3 percent of the total flow of the Eel River) the impact is much larger during the dry season, when the Eel’s already low natural flows are further reduced by diversions.”

      • The next sentence in that quote is “Since 2004 the dams used by the project have been used to provide additional flow to the Eel River during the dry season, primarily to support fish populations.” So are they saying that the same release water above the natural flow in the dry season or that they continue diversion in the dry season? It’s confusing.

      • Who wrote the “wikipedia” article? There’s allot of propaganda concerning the PVP, they all have their reasons and are protecting their own private interests. Let me give you a couple of examples:

        The public will have no idea what is going on, or who controls what until the smoke clears. And there are allot of people, with allot of money gunning for the control of this water and its not Humboldt County…

        If it were up to me, I would make PG$E pay to tear it all down, but its more complicated than that. This system of dams, lakes and diversions has created a new ecosystem, that never existed before. Allot of thought will need to go into this, by someone without a dog in the fight. Have you seen the movie Chinatown? This project was no different during its inception or even today. A long time ago, someone once said; “Whiskey Is for Drinking; Water Is for Fighting Over”, I guess they knew what they were talking about…

  • Kym- if and when it’s available please include a link to the published study

  • I agree with Ed Voice above in questioning the data/foundation for the statement about post WWII logging being the culprit for the low flows and algae blooms.

    WTF!! No mention of the out of control green rushers and mega grows that for the last two decades have been withdrawing water at huge levels to feed these mega grows. The water primarily is taken from the cooler streams and creeks that feed the river, so even more of a problem. In addition, being withdrawn during the most critical time of the year….late summer and fall, when the fish are starting to stage for their runs up the river.

    I say (without any proof mind you) that this type of diversion is more of the cause of our current situation than that from past logging. Some of these grows are into the 20,000 – 30,000 plant range, just one grow! that is a ton of water. Couple this with the over use of pesticides, herbicides, and rodenticides and you have all kinds of chemicals being dumped into the river system making algae blooms more prevalent.

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