Extremely high microcystin level detected in Barnes Unit water sample

KLAMATH FALLS, Ore. – ODFW is urging waterfowl hunters and other visitors to use extreme caution after laboratory results revealed exceptionally high levels of microcystin in a water sample collected from the Barnes Unit of the Upper Klamath National Wildlife Refuge.

The sample was taken from an area currently open for waterfowl hunting during the 2025–2026 season.

Microcystin is a cyanotoxin produced by certain harmful algal blooms. Exposure can cause acute liver damage in people and is often fatal to dogs.

ODFW reminds hunters and other visitors that:

• People and pets should avoid contact with water that appears scummy, discolored, or contains visible algal mats.
• Dogs are particularly vulnerable and should be kept away from affected water and from licking wet fur after exposure.
• Hunters should avoid using contaminated water for cleaning gear or handling harvested birds.
• Symptoms of microcystin exposure can include vomiting, diarrhea, weakness, and seizures in dogs, and stomach pain, nausea, vomiting, or liver complications in people.