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Clear Lake’s (and the World’s) Algae Problem

The problem began in earnest in the late-1920s, when heavy earth-moving equipment set about filling and re-sculpting Clear Lake's shoreline wetlands to “reclaim” them for agriculture, Bradley Mining Company inaugurated an era of intensive open-pit mercury mining outside of Clearlake Oaks, and road construction (and accompanying instream gravel mining) increasingly converted the surrounding landscape into prime habitat for the automobile.

The soil particles disturbed by these activities invariably entered the numerous creek channels that feed the lake. Within a remarkably short period, roughly 85% of the lake's marshes and other wetlands — natural filtration systems, which had existed for thousands of years — had disappeared. According to a 2007 core-sample study by members of UC Davis' ecology professoriate, the volumes of phosphorus and nitrogen that washed into the lake post-1927 increased by a factor greater than ten.

Thus did Blue-green algae blooms start to emerge on a large scale in Clear Lake: widely considered the oldest lake in the United States. Also referred to as Cyanobacteria, the algae thrives in calm, warm, and nutrient-rich waters, which the lake that characterizes Mendocino County's neighboring county provides in abundance.

The year 2014 has seen the highest average temperatures in California since official record-keeping began in the late-1870s. It is also, of course, a year of epic drought. California's agribusinesses are heavily dependent on nutrient-laden fertilizers and pesticides of precisely the sort that foster cyanobacteria blooms. Invariably, cyanobacteria has emerged once again in Clear Lake in the last month. So, too, have other waterways and standing water bodies in the state seen algae blooms.

Cyanobacteria are photosynthetic bacteria that can create a variety of water quality problems, including lowering dissolved oxygen levels and production of toxins (called cyanotoxins). Cyanotoxins have caused wildlife mortality, including in sea lions, and they have contributed to liver cancer and tumors in humans.

The extent to which cyanobacteria pose a health hazard is a source of contention, however. There are untold thousands of types of blue-green algae. Many of them act as little more than a visual nuisance. The known cases of health problems from cyanotoxins are few. In specific areas of California, including some parts of the California Central Coast and the Klamath River basin, the impacts have been more notable.

Lake Pinto in the Santa Cruz County town of Watsonville, for instance, is known for the highest levels of microcystin — the most commonly occurring class of cyanotoxins — in California and possibly the US. The area produces more strawberries than any other region of the country. The agribusinesses in question heavily use fertilizers and pesticides, thereby causing a huge spike in the lake's nutrient levels and, consequently, its cyanobacteria levels.

In addition, blue-green algae is also one factor among several, according to various state, federal, and tribal agency analyses, that likely contributed to the mass die-off of Klamath River salmon in 2002. That year, at least 68,000 adult Chinook salmon died — primarily from a disease called “gill rot” when returning to the river to spawn. Although the primary cause of the problem was warm water temperatures and low flows, resulting from the George W. Bush administration's decision to export prodigious volumes of water to agribusinesses, fluctuations in pH (acidity/alkalinity) and dissolved oxygen levels were also factors in weakening the fish — problems to which the algae directly contribute.

One close observer of the problem in Clear Lake is Sarah Ryan, environmental director at the Big Valley Rancheria Band of Pomo Indians. In early-September, Big Valley Rancheria and the Elem Band of Pomo Indians jointly initiated a task force to monitor cyanobacteria levels in Clear Lake. The task force includes participants from Lake County, Clearlake (the town), Lakeport, and federal and state agencies. In the last four weeks, these parties have conducted weekly monitoring in various areas of the lake.“If there's no monitoring, there's no info,” Ryan says. “The levels we are seeing in Clear Lake are very high in many spots.”So far, the task force has found water around the shorelines of Austin Park, Sulfur Bank Mine Beach (near Clearlake Oaks), and in Clearlake Oaks to show levels of microcystins well above those considered safe for swimmers. As a result, “warning” signs are being posted in those areas. A sample taken near Clearlake Oaks last week contained the most highest cyanobacteria cell counts so far: 17,000 parts per billion (ppb).

By comparison, the highest concentration discovered in the aforementioned Lake Pinto is 2.893 billion ppb. The World Heath Organization considers 20 parts per billion a moderate health risk for recreational use. With regard to drinking water, the WHO regards one part per billion as risky, whereas the State of California has set the threshold at .8 ppb.

The Lake County task force also tested drinking water drawn from the lake for microcystins, the most common cyanotoxin. County and city officials have fielded a number of complaints about the water's taste and odor from local residents in recent months. All four locations that were tested — City of Lakeport, Highlands Water Company, Clearlake Oaks Water Company and Konocti County Water District — measured “non-detectable” for microcystins in finished water.

A Global Problem

Among the various scientists to study Clear Lake's algae problem is Dr. Vladamir Novotny, who directs the Center for Urban Environmental Studies at Northeastern University in Boston. A world-renowned expert on cyanobacteria in water bodies, Dr. Novotny provided a review of a 2002 plan proposed by the Virginia-based corporation TetraTech, which was adopted by the State of California in 2006, for monitoring and reducing Clear Lake's elevated nutrient levels. Novotony was critical of the TetraTech plan.

As Novotny notes, the main contributing factors to cyanobacteria blooms are increasingly common throughout the world: agricultural fertilizer and pesticide run-off, municipal sewage run-off, a rapidly warming planet, and even household cleaning products (destruction of wetlands, of course, is another). Novotny has closely evaluated cyanobacteria's causes and consequences in Central Europe's largest reservoirs, in the Florida Everglades, China, and elsewhere. “In the last twenty years, the problem has reached alarming proportions on a large scale,” Novotny told the AVA. “Harmful algal blooms are becoming endemic in Europe, Asia, and the US.” As Novotny notes, the problem has become more intractable over time. To understand why, it helps to know a few terms commonly used by ecologists: “eutrophic” and “hypereutrophic.” The former refers to a water body rich in nutrients and so supporting a dense plant population. The latter refers to a water body that has become impaired by excessive nutrient concentrations (usually of nitrogen and phosphorus), which render it undesirable for drinking water and other needs.

Along with other leading members of his field, Novotny has come to a devastating conclusion vis-a-vis the feasibility of remedying the cyanobacteria problem. Hypereutrophic water bodies tend to generate forms of cyanobacteria that hibernate in sediment, located in the beds reservoirs and lakes. Unlike forms of cyanobacteria that die off when run-off into the given water body declines, those that hibernate in sediments continue to re-emerge. Simply reducing new nutrient inputs into the water body can have little impact on them.

“You're not only dealing with the influx of nutrients,” Novotny said of hypereutrophic water bodies. “You are dealing with the sediments already in the water bodies, where the cyanobacteria have become established. It can become very difficult and expensive to remove them.”In spite of intensive and extremely expensive efforts to reduce nutrient run-off into the Czech Republic reservoirs and the US's Lake Erie, for instance, Blue-green algae in these hypereutrophic water bodies remains a chronic problem. In one case, the Czech Republic drained a reservoir and hired a fleet of excavators and dumptrucks to remove the sediment. Three years later, the cyanobacteria returned.

Dr. Novotny's most recent journal article, entitled “Advanced (hyper)eutrophication and harmful algal blooms in impoundments — a worldwide problem, its causes and consequences,” provided the following summary of cyanobacteria's increasing number of strongholds within the US: “Cyano-HABs have been ubiquitous in the St. Johns River, Lakes Okeechobee, Apopka and hundreds of smaller lakes in Florida, in the Delaware Reservoir (in 1990s) providing water to New York City, Onondaga Lake in New York State, in the 1980s in Lake Mendota and Lake Delavan, and today Lake Butte des Morts in Wisconsin. They have been recently found in the Charles River in Boston. In the early 2000s, 16% of lakes in Florida were classified as hypereutrophic.”He continued, “The Cyano-HABs have reappeared now also in Lake Erie of the Great Lakes, and the number of cyanobacteria infested water bodies increased during the record breaking hot spell in the south and southwest US. The largest fresh water lake in California, Clear Lake, was eutrophic at the beginning of this century with occasional growth of cyanobacteria.”Novotny further wrote, “[Clear Lake has] provided potable water to several communities and fishing and swimming benefits to the users. Because the responsible agencies failed to protect the lake… today the lake is hypereutrophic, exhibited by massive Cyano-HABs and uses have diminished.”

Mismanagement in Lake County?

Until quite recently, many Lake County officials were all but proclaiming the problem to be over. Even Lake County UC Cooperative Extension Director Greg Giusti, currently a Jerry Brown-appointed member of the North Coast Regional Water Quality Control Board, wrote in a 2008 summary of historic human impacts on Clear Lake's aquatic health that the “county's aggressive approach to erosion control efforts” was “finally abating the chronic nuisance algae.” The following year, the algae blooms returned with a vengeance. They have persisted since then as Lake County's most vexing and widely-known ecological and political problem.

Clear Lake acts as a powerful representative of the greater global problem of cyanobacteria, owing partly to a unique and compelling natural history. The lake is not only widely believed to be the oldest lake in the United States; with a surface area of 68 square miles, it is the largest natural freshwater lake entirely in California.

At one time, the lake arguably enjoyed far greater stature than it does today. Scenes of sheep farms along the lake, or tree-fringed shorelines with the lake's smooth expanse of water rising against an unbroken line of misty hills, and similar images, were popular photographs in 20th century California. Among those who contributed to this popular association of Clear Lake with romantic pastoralism, viewed as increasingly rare in the popular consciousness (even then), was arguably the most influential photographer of the 20th century, Edward Weston. During the mid-20th century, Clear Lake's shores became akin to a blue collar Riviera for the San Francisco Bay Area's working classes.

In many respects, the lake is actually in far better condition than in the 1950s and 60s, when a combination of septic system seepage and applications of heavy pesticide sprays in an attempt to control gnats merited Clear Lake a mention in Rachel Carson's famed 1962 book Silent Spring. Carson cited examples of DDT applications that had caused mass die-off of Western Grebe's and other Clear Lake wildlife. Banning DDT and construction of modern sewage treatment facilities have done a lot to clean things up.

The lake's persistent problem with cyanobacteria, however, is a major problem especially when viewed against a backdrop of global contamination of water supplies with cyanotoxins. And the failure to prevent them raises numerous questions about the ability and willingness of the Lake County power structure to deal with the problem. Next week, I'll examine the recent history of official efforts to prevent the algae blooms, and how it reflects on the powers-that-be within the relevant federal, state, and county regulatory agencies and governments.

(Contact Will Parrish at


  1. Fran Ransley October 24, 2014

    This is one of the best written articles I’ve seen recently on cyanobacteria issues, and unlike many scientific papers, it is simple enough for any lay person of average intelligence to understand. Other than a couple of minor errors probably due to the omnipresent autocorrect, it is excellent.
    “…chronicle nuisance algae.” I think you meant “chronic.”
    I hope for future articles that you will get a chance to interview Dr. Harry Lyons. He’s had his eye on these issues for a long time, and he’s very articulate.

    • AVA News Service October 27, 2014

      Typo corrected. Thanks for letting us know.

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