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State, regional boards outline expanded monitoring and response for harmful algal blooms
Summary
State and regional water board staff described expanded monitoring, remote sensing, community science and proposed Bay-Delta Plan provisions aimed at improving detection, public warnings and longer-term controls for cyanobacterial harmful algal blooms across California.
State and regional water board officials described a patchwork of monitoring and new program work aimed at faster detection and public warnings for harmful algal blooms (HABs), while identifying long-term data gaps that will shape future regulation.
The state office of Information Management and Analysis said current HAB work is largely reactive: local partners report suspected blooms, staff confirm and post risk communications, and limited laboratory testing establishes whether toxins are present. The program established under SB 834 pays for regional event response but lacks enough resources for proactive, statewide surveillance and follow-up sampling, officials said.
State staff emphasized that freshwater cyanobacterial blooms (cyanobacteria, often called “blue-green algae”) and estuarine events show different behaviors: benthic mats on substrates and floating planktonic blooms have different exposure pathways and require different monitoring. Officials described a two-tiered approach: event response teams to validate reported blooms and a longer-term plan to expand remote sensing, routine holiday pre-season checks of popular recreation sites, and linkages to federal and university monitoring networks.
The Division of Water Quality said a major next step is shifting some policy work from nutrient numeric objectives toward cyanotoxin-focused objectives and biological condition assessments that can be used to measure harmful effects and guide implementation. That approach would start by developing toxin-specific water-quality objectives and then working on implementation measures to reduce algal biomass, taking into account temperature, flow and shading.
Delta and Bay-specific work was highlighted: the draft 2024 Bay-Delta Plan includes proposed CHAB monitoring provisions that would require targeted phytoplankton and cyanotoxin sampling at identified hotspot locations (for example, Stockton Waterfront, Franks Tract, Victoria Canal and Mildred Island), initially relying on major water-right holders such as the State Water Project and Central Valley Project to implement monitoring during bloom seasons. The Board has contracted USGS to prepare a monitoring design report to help design a coordinated Delta-wide monitoring program and predictive models.
Regional teams described pilot work in remote sensing, a NOAA-funded Bay-Delta data dashboard to integrate many data streams, and community science partnerships (for example, Restore the Delta and tribal groups) that train volunteers to collect visual indices and samples for follow-up lab confirmation. The Division of Drinking Water said it is developing notification and response levels (recommended reporting thresholds) based on OEHHA guidance and is preparing lab methods (including a total saxitoxin method) and intake monitoring guidance for public water systems.
Panelists reported frequent detection of blooms in “backwater” and dead‑end channels of the Delta where residence time and warm, low-flow conditions favor cyanobacteria. They warned that current monitoring is not deep enough to determine trends statewide and called for more resources to answer key management questions: which management actions reduce blooms and toxins, where to prioritize mitigation, and how to integrate remote sensing with on-the-ground sampling.
Officials said immediate priorities are expanding lab capacity for toxin testing, finalizing the Delta monitoring design, building the Bay-Delta dashboard for integrated visualization, and piloting mitigation trials (for example, small mesocosm hydrogen‑peroxide tests for planktonic blooms). They cautioned that benthic mats—common in rivers and some reservoirs—pose different mitigation challenges and that many mitigation technologies are currently reactive and short-term.
The panel urged counties, local water managers and tribes to maintain lines of communication with State and regional boards so public-health advisories, sampling and signage can be put in place quickly. Board staff said the approach going forward will be to combine event response, strategic monitoring at hotspots, improved remote sensing validation and longer-term research to inform future regulatory options.
