Klamath River 2007 Blue-Green Algae Summary.pdf

Water samples collected by the Yurok Tribe Environmental Program (YTEP), the Karuk Tribe, BOR, and PacifiCorp detected Microcystis aeruginosa (MSAE) and its toxin microcystin throughout the river from downstream of Upper Klamath Lake to the estuary. Microcystin levels exceeded World Health Organization (WHO) risk guidelines in all monitored reaches. MSAE is a cyanobacterium that releases hepatoxin microcystin upon decomposition, causing health effects in humans and animals including rash, irritation, nausea, vomiting, liver damage, and potentially death. WHO establishes risk thresholds: low risk (20,000 cells/mL, 4 µg/L), moderate risk (100,000 cells/mL, 20 µg/L), and severe risk (10,000,000 cells/mL or visible scum, 200 µg/L). The toxin bioaccumulates in liver and muscle tissue, with chronic exposure causing liver damage. Sampling used churn splitters with Lugol's preservative for algae identification and frozen samples for microcystin testing. Tribal subsistence fishers face heightened exposure risk during salmon runs due to increased contact with contaminated waters. The report highlights significant water quality impairment and health concerns across the Klamath River system.