Humboldt County environmental health officials are warning residents to avoid stagnant areas of local waterways after a dog died shortly after swimming in a slow-moving pool of the Eel River near Scotia on Thursday, July 23. The incident comes as conditions become increasingly favorable for cyanobacteria — microscopic, photosynthetic bacteria commonly known as blue-green algae — and the harmful algal blooms they can produce. Warnings are typically issued in late July or early August, when low river flows and prolonged high temperatures can contribute to cyanobacteria growth in rivers and lagoons.

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• Lost Coast Outpost (Eureka, Calif.): Dog dies after swimming in Eel River; health officials warn of harmful algal blooms