Harmful Algal Blooms in Clear Lake, California – Circle of Blue

Though poisonings from drinking water are rare, simply being at the lakeshore when blooms are present is a risk. Touching certain cyanotoxins can cause rashes and allergic reactions. That’s why the U.S. Environmental Protection Agency published its guidelines for recreational water. It’s also why the tribes wanted more information about what their members might be exposed to during their ceremonies.

Health hazards do not end with skin contact. In a peer-reviewed study published in April, researchers found that a harmful algal bloom on Nantucket Island, Massachusetts, was releasing anatoxin-a, a neurotoxin, into the air. The researchers speculate that sharp winds sent the toxin airborne, but it is unclear what effect inhaled toxins might have on human health.

The risk of aerosolized toxins is high enough that the Centers for Disease Control and Prevention will begin a study this year to assess airborne exposure in Florida residents who live or work on Lake Okeechobee, St. Lucie River, Caloosahatchee River, and Cape Coral canals — all places with a recent history of severe blooms. Results are expected in 2023.

Though most attention is directed at phosphorus, Paerl says that nitrogen should not be neglected, either. Nitrogen is more manageable, Paerl told Circle of Blue. It can be cut more easily by restricting polluted runoff from streets, farm fields, septic systems, and wastewater treatment plants, while also minimizing erosion. Paerl has studied harmful algal blooms in large lakes worldwide, from Lake Erie to Lake Taihu, in China.

“That’s one thing we are prescribing for many of the large lakes that Clear Lake fits into: not only to reduce phosphorus inputs because it takes so long for the system to clear itself of phosphorus,” Paerl said. “But also deal with nitrogen.”

There is an official process in this country for these nutrient diets. It’s called a total maximum daily load, or TMDL. Written into the federal Clean Water Act, TMDLs are a regulatory tool for reducing pollution in a waterbody. Some TMDLs apply to stream segments of fewer than a dozen miles; others, like the one for the Chesapeake Bay, encompass entire watersheds.

Clear Lake has a nutrient TMDL that was put in place in 2007, but for phosphorus only. It identifies forest roads, country and federal lands, and irrigated agriculture as primary sources of sediment erosion.

Nearly a decade ago, Ryan warned state officials that the TMDL was not effective.

“It is obvious that the measures being taken by the communities in the Clear Lake Basin are not reducing nuisance algal blooms,” Ryan wrote to the State Water Resources Control Board on August 20, 2012.

Karola Kennedy, her partner in developing the cyanobacteria program, also notified the Water Board of concerns about the TMDL. She said that projects to control erosion were not being monitored to assess whether they lived up to their promises. Kennedy did not want the state to extend compliance dates for reducing nutrient flows, which it is still considering.

“The Elem Indian Colony Tribal community does not want to wait another generation for compliance on the nutrient TMDL,” Kennedy wrote on October 3, 2017. “Water quality issues have exponentially worsened in the past decade. We are fearful of what is to come if the responsible parties are given a pass for another generation.”

Kennedy, now the water resources manager for Robinson Rancheria, another Clear Lake tribe, told Circle of Blue that the lack of monitoring for erosion control is still a problem today. “It’s hard to say if those best management practices are truly that. If you don’t monitor them, you can’t manage it.”

The Central Valley Regional Water Quality Control Board is the state agency that oversees the TMDL. Adam Laputz, the board’s assistant executive officer, told Circle of Blue that the board is reviewing the TMDL to see if it should be extended or revised. Laputz said that any revisions would take into account new research in the last 15 years on the causes of harmful algal blooms and could include nitrogen limits or changes to the amount of phosphorus allowed into the lake. But given all the factors that feed the blooms — nutrients, water temperature, wind and water currents — determining whether the TMDL has been effective “is a very difficult question to answer,” Laputz said.

One major project that aims to prevent more nutrient-laden sediments from flowing into the lake and to reverse the loss of wetlands is the restoration of a marsh ecosystem downstream of Middle Creek and Scotts Creek. Located at the northern end of the lake, the site contributes about 70 percent of the sediment and phosphorus that flow into the lake. By one estimate, restoring 1,400 acres of marsh where there are now fields and levees could increase the lake’s wetland coverage by 70 percent and reduce phosphorus inputs for the lake’s upper basin by 28 percent. Those reductions are only on paper right now. The county is still acquiring land for the project and has not started construction.

The Middle Creek restoration is an important step, but larger schemes could be on the horizon. In 2017, an act of the Legislature established a 15-member Blue Ribbon Committee to discuss the restoration of Clear Lake. The act also funded an in-depth research program that is being led by the University of California, Davis. The goal of the program is to observe how water and nutrients move throughout the watershed.

The California Natural Resources Agency said it is working on a grant that will extend funding for the program, which needs more data before it can fine-tune a working model of the watershed and lake dynamics. According to Geoff Schladow, the research program’s principal investigator, the model will provide glimpses of the future. Once the model is running, researchers can tweak variables like nutrient inputs, wind speed, and air temperature to test their effect on the blooms, which tend to concentrate in two of the lake’s sub-basins, the Oaks Arm and Lower Arm. That way, local agencies could issue cyanobacteria forecasts, directing swimmers and boaters away from hazardous areas and warning tourists coming up from San Francisco for the weekend about which beaches to avoid. The tribes, though, cannot simply change the location of their ceremonies.

One theory is that blooms proliferate in the Oaks and Lower arms because the lake is deeper there and phosphorus in the lakebed sediment becomes unbound when oxygen is depleted. This “internal loading,” a legacy of centuries of erosion, is actually the largest source of phosphorus available to fuel cyanobacteria growth in the lake. Schladow said a potential remedy is to inject oxygen in these areas when levels reach critical thresholds. But researchers won’t know whether that’s the case until their model is complete and they can run tests. The results matter not just for scientific discovery but also for fiscal responsibility.

“The truth of the matter is lake remediation costs a lot of money and you can’t afford to get it wrong,” Schladow told Circle of Blue.

Angela De Palma-Dow, the invasive species coordinator for the Lake County Water Resources Department, reiterated that point. Lake County is one of the poorest in California, and there is not a lot of spare cash to throw at false solutions.

“It’s hard for us to put money into a project and have it have a negligible impact on water quality,” De Palma-Dow told Circle of Blue. She hopes the UC Davis study will provide recommendations that are “targeted and relevant.”

Researchers who study Clear Lake are full of praise for the program that Ryan and Kennedy started. It’s hard to imagine so much legislative and scientific attention directed at the lake if not for the work of the tribal governments.

“The fact they’ve been collecting data has raised the awareness in the whole community,” Schladow said. “We would be a long way further back if it wasn’t for those efforts.”

Local officials acknowledge that the tribes are providing a public service that they are not able to fulfill.

“Frankly, there’s no way our county would be able to do that work and we rely heavily on them and what they do,” De Palma-Dow said. “They’re great partners.”

Ryan said that it took many years of cajoling before those partnerships took root and bore fruit. She’ll keep pushing colleagues in county and state agencies, because after all, science without government action to back it up is just not enough.

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