Big Valley Band of Pomo Indians details Clear Lake HAB monitoring, reports toxins in water and fish
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Summary
Big Valley Band of Pomo Indians described a tribal‑led Clear Lake monitoring program that began in 2014, documented high microcystin detections in ambient water and fish tissue, found cyanotoxins in some private tap water intakes, and has used signage, community outreach and partner research to inform public health and tribal food‑safety decisions.
Sarah Ryan, environmental director for the Big Valley Band of Pomo Indians, described a tribal‑led monitoring program on Clear Lake and its tributaries that began in 2014 after unusually high toxin detections and community concern. "We started a Clear Lake cyanobacteria task force" and expanded sampling, Ryan said, adding that tribal partners initially used field test strips and microscopy and later sent samples for lab analysis of multiple cyanotoxins.
Ryan presented laboratory results the tribe collected over multiple years, including early analyses she described as "over 2,000 parts per billion" for total microcystin in some samples — well above the caution and danger thresholds the presenters discussed. She said the tribe found detectable microcystin in fish tissue: in a 2017–2023 sample set of 79 fish across 10 species, 65% contained detectable microcystin. Ryan also reported that some private tap water intakes drawing directly from Clear Lake had measurable cyanotoxins after household treatment, and that the team partnered with UC Davis and other researchers on a biomarker study and fish‑tissue analysis.
The Big Valley program uses a mix of grab samples, SPAT bags (for benthic toxin accumulation), microscopy, continuous data loggers and public signage with QR codes linking to the tribe's data portal. Ryan said the tribe's outreach included a Clear Lake Water Quality Facebook page and collaboration with county public‑health officials to update advisory language and signage — changes intended to avoid language such as "no bloom, no problem" when toxins may be present without visible scums.
Ryan described outreach and studies funded through CalEPA and CDC grants, noting a 2021 outreach and tap‑water testing effort that prompted a joint press release with county officials advising some residents not to drink untreated lake water in affected areas. She said the tribe tracks fish kills, has documented large summer fish‑kill events, and uses data loggers to show dissolved oxygen drops during bloom die‑offs, which correlate with fish mortality.
Ryan urged other tribal and local monitoring programs to build microscopy and field sampling capacity, and offered Big Valley's experience as a model for tribal‑led monitoring paired with state partner support.